Naturally occurring radioactive materials associated with unconventional drilling for natural gas

Transcription

1 University of Iowa Iowa Research Online Theses and Dissertations Spring 2016 Naturally occurring radioactive materials associated with unconventional drilling for natural gas Andrew Wyatt Nelson University of Iowa Copyright 2016 Andrew Wyatt Nelson This dissertation is available at Iowa Research Online: Recommended Citation Nelson, Andrew Wyatt. "Naturally occurring radioactive materials associated with unconventional drilling for natural gas." PhD (Doctor of Philosophy) thesis, University of Iowa, Follow this and additional works at: Part of the Toxicology Commons

2 NATURALLY OCCURRING RADIOACTIVE MATERIALS ASSOCIATED WITH UNCONVENTIONAL DRILLING FOR NATURAL GAS by Andrew Wyatt Nelson A thesis submitted in partial fulfillment of the requirements for the Doctor of Philosophy degree in Human Toxicology in the Graduate College of The University of Iowa May 2016 Thesis Supervisor: Associate Professor Michael K. Schultz

3 Graduate College The University of Iowa Iowa City, Iowa CERTIFICATE OF APPROVAL This is to certify that the Ph.D. thesis of PH.D. THESIS Andrew Wyatt Nelson has been approved by the Examining Committee for the thesis requirement for the Doctor of Philosophy degree in Human Toxicology at the May 2016 graduation. Thesis Committee: Michael K. Schultz, Thesis Supervisor Tori Z. Forbes R. William Field Michael D. Wichman Adam S. Ward

4 I dedicate this thesis to my friends, family, and colleagues. This work would not have been possible with out their financial, emotional, and intellectual support. ii

5 In nature nothing exists alone. Rachel Carson Silent Spring iii

6 ACKNOWLEDGEMENTS First, I would like to acknowledge my wife, Leah Feazel, for listening to my endless thoughts on the environmental radiochemistry of unconventional drilling. Secondly, I would like to acknowledge my thesis advisors. Dr. Schultz provided me the academic freedom and support to pursue my ideas. Thank you Dr. Schultz for nurturing and promoting my academic development. Thank you Dr. Tori Forbes for going over and beyond your departmental duties and contributing to my academic success. Drs. R. William Field, Michael D. Wichman, and Adam S. Ward, thank you for your support; your thoughts have been valuable in shaping this thesis. Third, I would like to acknowledge everyone who assisted me in the laboratory. Although not a complete list of people who helped along the way, I would especially like to thank Andrew Knight, Eric Eitrheim, Dustin May, Madeline Basile, Ashini Jayasinghe, Mengshi Li, Kyle Kloepping, Amanda Carl, Michael Birmingham, Marinea Mehrhoff, Robert Shannon, Robert Litman, and Adam Johns. Lastly, I would like to thank the program directors and administrators of the Interdisciplinary Human Toxicology Program and the Presidential Graduate Research Fellowship program. Special thanks to Dr. Larry Robertson, Dr. Gabriele Ludewig, Dr. Peter Thorne, Dr. Daniel Berkowitz, Dean John Keller, and Ms. Kathy Klein-Gerling. Without your support, this thesis would not have been possible. iv

7 ABSTRACT As unconventional drilling has emerged as a major industry in the US and around the world, many environmental health and pollution risks have surfaced. One emerging concern is the risk of environmental contamination arising from unconventional wastes that are enriched in naturally-occurring radioactive materials (NORM). Although NORM has been a well-documented contaminant of oil and gas wastes for decades, there are new challenges associated with unconventional drilling. This thesis discusses several of these challenges, focusing on NORM from black shale formations. Chapter 1 provides background information on environmental radioactivity and unconventional drilling. Chapter 2 describes the potential for NORM to migrate into groundwater around unconventional drilling operations. Chapters 3 and 4 describe radiochemical methods developed for the analysis of Marcellus Shale unconventional drilling wastes. Chapter 5 describes environmental partitioning of Marcellus Shale unconventional drilling wastes. Collectively, this thesis attempts to broaden the scientific understanding of NORM in unconventional drilling wastes so that potential environmental impacts may be mitigated. v

8 PUBLIC ABSTRACT Unconventional drilling, commonly referred to as hydraulic fracturing or fracking, has emerged as a major industry in the US and around the world. This industry is aimed at extracting energy (in the form of natural gas or oil) from deep below the earth s surface in previously unreachable geologic formations. As this new industry grows, many environmental health and pollution risks have surfaced. One emerging concern is the risk of environmental contamination arising from liquid and solid wastes that are enriched in naturally-occurring radioactive materials (NORM). Although NORM has been a well-documented contaminant of oil and gas wastes for decades, there are new challenges associated with unconventional drilling. This thesis discusses several of these challenges. Collectively, this thesis attempts to broaden the scientific understanding of NORM in unconventional drilling wastes so that potential environmental impacts may be mitigated. vi

9 TABLE OF CONTENTS LIST OF TABLES... xii LIST OF FIGURES... xiii PREFACE... xv CHAPTER 1: NATURALLY-OCCURRING RADIOACTIVE MATERIALS (NORM) ASSOCIATED WITH UNCONVENTIONAL DRILLING FOR SHALE GAS Abstract Introduction NORM NORM in Marine Black Shales Partitioning in the Subsurface Uranium Series Partitioning at Depth Thorium Series Partitioning at Depth Radioactive Decay, Equilibrium, and Ingrowth Radioactive Decay Radioactive Equilibrium Radioactive Ingrowth Major Stages of Unconventional Drilling Water Acquisition Chemical Mixing Drilling Injection Flowback and Flaring Treatment Research Needs Fate and Transport of 226 Ra-decay Products in Aqueous Environments Behavior and Composition of NORM in Solid Waste Potential Regional Impacts of 222 Rn Conclusion Addendum: Basic Properties of NORM vii

10 Uranium Protactinium Thorium Actinium Radium Radon Polonium Bismuth Lead Thallium References CHAPTER 2: MONITORING RADIONUCLIDES IN SUBSURFACE DRINKING WATER SOURCES NEAR UNCONVENTIONAL DRILLING OPERATIONS: A PILOT STUDY Abstract Introduction Materials and Methods General Sampling Description Determination Radionuclide Activities Results and Discussion Uranium Lead and Polonium Limitations Conclusions Acknowledgments References CHAPTER 3: MATRIX COMPLICATIONS IN THE DETERMINATION OF RADIUM LEVELS IN HYDRAULIC FRACTURING FLOWBACK WATER FROM MARCELLUS SHALE Abstract viii

11 3.2. Introduction Materials and Methods General Flowback Wastewater Sample Surrogate Matrix Methods of Analysis Tested Results and Discussion Chemical Matrix Barium Sulfate Coprecipitation M Empore Radium RAD Disks MnO2 Preconcentration Rn Emanation Measurement by RAD HPGe Gamma Spectroscopy Acknowledgment References CHAPTER 4: UNDERSTANDING THE RADIOACTIVE INGROWTH AND DECAY OF NATURALLY OCCURRING RADIOACTIVE MATERIALS IN THE ENVIRONMENT: AN ANALYSIS OF PRODUCED FLUIDS FROM THE MARCELLUS SHALE Abstract Background Objective Methods Results Conclusions Introduction Methods General Tracers and Standards Sample Description High Purity Germanium (HPGe) Gamma Spectrometry ix

12 Alpha-Emitting Radionuclides MnO2 Coprecipitations Method 1: SR Resin and Silver (Ag) Autodeposition Separation of Polonium Method 2: TRU-Ag-TEVA Separation (Final Method) Method 3: TRU-TEVA for Separation of U and Th Isotope Dilution Alpha Spectrometry Radioactive Ingrowth Modeling Results Radiochemical Disequilibria and Ingrowth Discussion Modeling the Partitioning NORM in Marcellus Shale Th Series Partitioning U Series Partitioning Conclusion Acknowledgements References CHAPTER 5: PARTITIONING OF NATURALLY-OCCURRING RADIONUCLIDES (NORM) IN MARCELLUS SHALE PRODUCED FLUIDS INFLUENCED BY CHEMICAL MATRIX Abstract Introduction Experimental Results and Discussion Field Data NORM in Produced Fluids Environmental Fate of NORM Acknowledgements References CHAPTER 6: CONCLUSIONS Conclusions Chapter 1: Summary x

13 6.3. Chapter 2: Summary Chapter 3: Summary Chapter 4: Summary Chapter 5: Summary Future Directions Future Studies in Liquid Wastes Future Studies in Solid Wastes APPENDIX 1: SUPPLEMENTAL MATERIAL FOR CHAPTER APPENDIX 2: SUPPLEMENTARY INFORMATION FOR CHAPTER S2.1. Expanded Methods S Polonium-210 In-Growth S Thorium-228 In-growth S Uranium Absent S2.2. Supplementary References APPENDIX 3: SUPPLMENTARY MATERIAL FOR CHAPTER S3.1. SI Materials and Methods S General S HPGe Sediment S Polonium and Uranium Preconcentration S Thorium Preconcentration and Separation S Lead S Alpha Spectrometry S Grain size S PXRD S High Resolution Transmission Electron Microscopy S Flowback Filtration U, Th, Ra, Pb, Po S Sediment Sequential Extraction of Ra S Sediment Sequential Extraction of Ba, Pb, Po S Ionic Strength and Ra Partitioning S3.2. Supplementary References xi

14 LIST OF TABLES Table 1-1 Naturally Occurring Radioactive Materials of Interest in Unconventional Drilling Wastes Table 2-1 Activities of Radionuclides from Selected Sites in Southern Colorado Table 3-1 Comparison of 226 Ra Quantitation Methods Table 4-1 Activity, Recovery, and Separation Method for Select Radioisotopes Analyzed by Alpha Spectrometry of Produced Fluids Table 4-2 HPGe Gamma Spectrometry of Produced Fluids Table S1-1 Sample Matrix Table S3-1 Chemical Analyses of Dunkard Creek Sediments Table S3-2 Alpha Spectrometry Dunkard Creek Sediments Table S3-3 High Purity Germanium (HPGE) Gamma Spectrometry of Dunkard Creek Sediments xii

15 LIST OF FIGURES Figure 1-1 The primordial decay series of interest in shale formations Figure 1-2 Uranium (U) trapped in marine organisms and sediments...48 Figure 1-3 Theoretical partitioning model of U and U decay products Figure 1-4 Equilibrium characteristics of selected NORM after a disequilibrium event Figure 1-5 Major stages of unconventional drilling Figure 1-6 Anticipated fates for 226 Ra and 226 Ra decay products in fresh water Figure 1-7 Oxidation of bit cuttings and other solid wastes Figure 1-8 Flaring of unwanted gases Figure 2-1 Activities of NORM in water collected from homes, a river and a municipal building in an area with unconventional drilling operations Figure 2-2 Schematic of possible NORM contamination pathways of groundwater near hydraulic fracturing operations Figure 3-1 Graphic Abstract...86 Figure 4-1 Natural thorium and uranium decay chains Figure 4-2 Activity and alpha spectra of Po, Th, and U Figure 4-3 Theoretical model of NORM partitioning and associated waste in Marcellus Shale Figure 4-4 Theoretical Bateman model of Ra decay product ingrowth and decay Figure 5-1 Dunkard Creek, WV, sampling locations Figure 5-2 Alpha and gamma spectrometry results for select samples near the discharge site at Dunkard Creek, WV Figure 5-3 Particulate and aqueous radiochemistry of Marcellus Shale produced fluids Figure 5-4 Ra and Ra decay products partitioning in Dunkard Creek sediments xiii

16 Figure 5-5 Theoretical depiction of Ba and Ra competition for adsorption on sediments in high and low Ba concentrations Figure S2-1 Schematic of Rapid Separation of U, Th and Po Figure S2-2 Representative Alpha Spectra Figure S3-1. General workflow for sequential extractions Figure S3-2. PXRD spectra for select sediments in Dunkard Creek Figure S3-3. PXRD of sediments from Quaternary Materials Laboratory at the University of Iowa Figure S3-4. Grain Size Triangle Plot of Sediments from Quaternary Materials Laboratory at the University of Iowa xiv

17 PREFACE Unconventional drilling for natural gas rapidly emerged as a major player in energy production in the United States, particularly between the years 2000 and The emergence of a new extractive industry raised numerous environmental health concerns about the potential health risks to workers and the general public, particularly with respect to liquid wastes generated by unconventional drilling. Health risks associated with wastes generated by extractive industries are often assessed by a risk assessment that consists of four steps: (1) hazard identification, (2) exposure assessment, (3) dose-response assessment, and (4) risk characterization. At the time this thesis work began, insufficient data was available to appropriately assess the health risks associated with exposures to unconventional drilling wastes. Some evidence was available that suggested naturally-occurring radioactive materials (NORM) released by unconventional drilling may present health hazards. The work presented in this thesis aimed to identify and characterize the radiological hazards associated with liquid wastes generated by unconventional drilling. In order to contribute to the quickly evolving science investigating the potential environmental impacts of this new industry, all of the chapters in this dissertation were published or submitted for publication in peer-reviewed academic journals prior to compilation of this dissertation. Consequently, the comprehensive review of the field in Chapter 1 does not explicitly lay out the experimental aims. In order to preserve the text in each chapter as published, the experimental aims are presented here in the preface. Chapter 1 provides a comprehensive review of environmental radiochemistry as it relates to unconventional drilling for natural gas. This chapter begins with a discussion on the history of NORM in the natural gas industry, and explaining the chemical processes that lead to partitioning of NORM in the subsurface. This is followed by a discussion of fundamental radiochemical decay and ingrowth processes. The remainder of the chapter discusses what is known about NORM in various stages of unconventional drilling. Lastly, the chapter discusses areas where research is needed. xv

18 Chapter 2 describes a pilot study that investigated the potential for NORM to migrate into drinking water resources in an area with numerous unconventional and conventional natural gas wells. This study does not provide conclusive evidence whether unconventional drinking does or does not increase NORM in groundwater; however, this study serves to highlight the challenges of studying NORM in groundwater near unconventional drilling operations. In depth discussion of methodological and study design challenges are described. Chapter 3 describes a laboratory-based study on the measurement of radium (Ra) isotopes in flowback/produced water from a Marcellus Shale unconventional drilling operation. Due to the high levels of total dissolved solids (TDS) and alkaline earth metals (barium (Ba) in particular), drinking water methods to measure Ra were hypothesized to underestimate the true value of Ra in the produced water. We tested this hypothesis by comparing five commonly used Ra-quantitation methods: (1) barium sulfate (BaSO4) coprecipitation, (2) manganese dioxide (MnO2) pre-concentration, (3) extraction chromatography, (4) radon emanation, and (5) high purity germanium (HPGe) gamma spectrometry. Results and discussion on the methodological challenges of measuring Ra in unconventional drilling produced waters are discussed. Chapter 4 describes a laboratory-based study on the measurement of alphaemitting radionuclides in produced water from a Marcellus Shale unconventional drilling operation. Although MnO2 pre-concentration and extraction chromatography did not work for the determination of Ra isotopes in these samples, we hypothesized that MnO2 pre-concentration followed by extraction chromatography would be an effective way to provide radiochemically-pure fractions of uranium (U), thorium (Th), and polonium (Po). We tested this chemical approach using isotope dilution techniques ( 232 U, 230 Th, and 209 Po). A summary of each chemical approach used, the pros and cons of each method, and the implications of the data obtained is discussed. Chapter 5 describes a laboratory-based study on the environmental partitioning of Ra isotopes in riparian sediments. Due to interferences observed in the measurement of Ra isotopes (Chapter 3), we hypothesized that Ra would not adsorb to sediments as predicted by traditional adsorption-desorption models. We tested this hypothesis by xvi

19 incubating a variety of sediments with Marcellus Shale produced fluids. We observed lower than expected levels of Ra adsorption to sediments. Further experiments described in this chapter attribute the lower-than-expected level of adsorption to ionic strength and chemical composition of the Marcellus Shale produced fluids. Chapter 6 provides a chapter-by-chapter summary and suggested future research directions. xvii

20 CHAPTER 1: NATURALLY-OCCURRING RADIOACTIVE MATERIALS (NORM) ASSOCIATED WITH UNCONVENTIONAL DRILLING FOR SHALE GAS This chapter was accepted for publication on 10 September, This chapter is reprinted with permission. Please refer to: Nelson, A.W.; Knight, A.W.; May, D.; Eitrheim, E.S.; Schultz, M.K. Naturally-Occurring Radioactive Materials (NORM) Associated with Unconventional Drilling for Shale Gas. ACS Books 1.1. Abstract As unconventional drilling has emerged as a major industry in the US and around the world, many environmental health and pollution risks have surfaced. One emerging concern is the risk of environmental contamination arising from unconventional wastes that are enriched in naturally-occurring radioactive materials (NORM). Although NORM has been a well-documented contaminant of oil and gas wastes for decades, there are new challenges associated with unconventional drilling. This chapter will present the origin of NORM in black shale formations. In addition, we present the fundamentals of radioactive decay and ingrowth, so as to provide a foundation for a discussion of the potential for environmental impact of NORM. Finally, within this context, we highlight keyrelatively-unexplored aspects of unconventional drilling that point to the need for further environmental radiochemistry research Introduction Hydraulic fracturing and horizontal drilling for shale gas has emerged as an important technology for supplying energy to the United States and the rest of the world (1-3). Amongst its benefits (for example, reduced land impact compared to conventional natural gas, (4) lower direct CO2 emissions than coal, (5) etc.), unconventional drilling has many unknown and uncharacterized potential environmental pollution risks (6-14). Of the least characterized environmental pollutants generated by new natural gas extraction techniques are naturally-occurring radioactive materials (NORM) (15). At depth, gas-bearing formations such as the Marcellus Shale (northeastern United States), often contain elevated levels of NORM, relative to the terrestrial environment at the 1

21 surface (16); Thus, the identification of elevated levels of NORM is frequently used as an environmental marker of petroleum rich reserves and used to guide drilling operations (17). However, as mining operations proceed to the extraction stage of well development, the relative enrichment in NORM in these materials has the potential to result in coextraction of these NORM (often referred to as technologically-enhanced naturally occurring radioactive materials (TENORM) (18). Co-extraction has the potential to lead to environmental contamination, bioaccumulation of radionuclides and radiation exposure to humans that would have otherwise been confined at depth. Thus, the proliferation of new horizontal drilling and hydraulic fracturing practices and technologies is leading to challenges associated with management of NORM. Some of these challenges, such as management of produced fluids, disposal of solid waste, and bioaccumulation of contaminants from oil and gas operations are well known from offshore drilling operations (19, 20). Other challenges are new and uncharacterized as drilling technologies originally developed for offshore operations are brought into the interior of the country (1). Developing understanding of and management strategies for NORM in these uncharacterized wastes will require input from interdisciplinary teams comprising specialists in industrial hygiene, toxicology, health physics, epidemiology, geology, petrology, atmospheric chemistry, environmental and civil engineering, policy, sociology, and radiochemistry. As radiochemists, our goal is to provide accurate and precise models of past, present, and future levels of radioactivity concentrations to inform appropriate waste management decision-making. Three related concepts are critical to understanding radioactivity concentrations in relation to NORM liberated by unconventional oil and gas mining: (1) geochemical partitioning of radionuclides in the natural decay series; (2) the resulting potential for disruption of natural steady-state radioactive decay relationships in the decay series (referred to as disequilibrium); and (3) the subsequent radioactive ingrowth that occurs after a disequilibrium event. To explain the concept of partitioning, we introduce the physicochemical properties of NORM and how these properties can result in geochemical partitioning (disequilibrium) of specific NORM in solid, liquid, and gas phases. Next, we describe radioactive ingrowth to explain how the radioactivity concentration of radioactive wastes have the potential to increase over time after a disequilibrium event. 2

22 We conclude with a discussion on the major phases of drilling as they relate to radioactivity and provide three research areas that are relevant to environmental public health. Thus, the goal of this perspective is to highlight some of the known challenges and to guide future investigations in environmental radioactivity related to unconventional drilling, with the goal of informing appropriate decision-making for waste management NORM The observation that certain elements are naturally-radioactive dates back to 1896, when Henri Becquerel discovered that uranyl-sulphate crystals spontaneously emitted radioactivity similar to X-rays (21). Madame Marie Curie later observed that all uranium and thorium isotopes were radioactive regardless of their chemical composition (22, 23). She also observed that uranium-containing mineral pitchblende possessed a higher level of radioactivity than compounds prepared from recently purified uranium. This observation prompted Marie Curie and her husband (Pierre Curie) to purify pitchblende and to characterize many of the radionuclides that are now collectively referred to as NORM. Many of the chemical properties that allowed the Curies to separate the various elements are important factors in environmental partitioning. We have provided a brief description of the physicochemical properties of the elements that comprise NORM to provide a basis for subsequent discussion on environmental partitioning (See Addendum: Basic Properties of NORM). We restrict our discussion to elements and isotopes from the three primordial decay series: (1) the actinium ( 235 U) series, (2) the thorium series ( 232 Th series), and (3), the uranium series ( 238 U series, sometimes referred to as the radium series). Note, that another important natural isotope 40 K (t1/2 = x 10 9 years) can be considered TENORM (24). 40 K will be present in all natural sources of K with a natural abundance of %. 25 Each of the primordial decay series is supported by an isotope with an extremely long half-life ( 235 U, 7.04 x 10 8 y, 232 Th 1.4 x y, 238 U 4.47 x 10 9 y) (25). Each of the three primordial NORM decay series noted above comprises a radiogenic progenitor, which supports a series of progeny radionuclides with varying half-lives (μs to millions of years) and different physicochemical properties (gas, particle reactive, 3

23 redox sensitive, etc.). In total amongst the three decay series there are 41 radionuclides from 12 different elements, where each radionuclide has unique decay modes and halflife, and each element has unique chemistry (26). Note, due to these physicochemical and radiochemical properties, each isotope has a different detection strategy (Table 1.1). All three of these decay chains will ultimately decay to one of three stable lead isotopes ( 208 Pb, 207 Pb, and 206 Pb) (Figure 1.1) (21). In general, the specific activity (radioactivity per gram of natural material; e.g., soil, sediment) of radionuclides in the actinium series is substantially lower than the specific activity of 232 Th and 238 U series radionuclides owing to the low natural abundance of 235 U (0.7% the mass of nat U) (25). Thus, we focus on NORM in the 238 U series (14 radionuclides, 8 elements) and 232 Th series (11 radionuclides, 8 elements) (26) NORM in Marine Black Shales The term shale generally refers to fine-grained-sedimentary clays and rocks that have widely differing biogeochemical morphologies and geologic ages (27). The types of shale of most interest to the petroleum and natural gas industries are the so-called, black shales, which are sedimentary rock deposits that became enriched in organic materials and metals originating from marine or brackish water (28). Black shales are characteristically dark in color owing to enrichment of organic content (which in some cases may exceed 10%) via multiple biogeochemical processes (Figure 1.2) (29,30). Over millennia, different biogeochemical processes (thermogenic and microbial), resulted in the reduction of the various organic materials into methane (natural) gas (31). The relatively high level of organic content in black shales is important not only for the production of natural gas, but also has implications for enrichment of NORM. The marine environment from which black shales typically arise are enriched in natural U isotopes ( nat U: 238 U, 235 U, 234 U), with an average of 3.3 μg nat U/L depending on ocean salinity in which the sediment was formed (32). While nat U behaves conservatively in oxic marine environments resulting in a conservative nat U and salinity correlations, this dissolved nat U is concentrated in organic-rich ocean sediments (for example, black shales) by the following mechanisms: (1) inorganic precipitation as U-rich marine waters pass across suboxic, organic-rich sediments (33), (2) microbiological reduction and 4

24 immobilization of nat U (34), and (3) sedimentation of marine organism detritus (35). As hexavalent uranyl (UO2 2+ ) is reduced to tetravalent (U 4+ ) at the anoxic/oxic boundary, insoluble complexes/minerals are formed that lead to enrichment of U in black shales (35). Thus, over millions of years, black shales are enriched in U and radioactive decay products in the U-series and are likely to be found in steady-state radioactive equilibrium with long-lived progenitors (26,36). Thus, at depth in the formation, one can expect that the decay rates of primordial progenitors and radioactive progeny are essentially the same (in secular equilibrium). On the other hand, anthropogenic activities, such as natural gas and petroleum mining in these formations have the potential to disrupt these steady state conditions by co-extraction of specific radionuclides in the primordial series i.e., partitioning of the specific progeny into the extracted liquid and gas phases in the mining process. Although shale formations vary in mineral composition and age, one can describe four overarching biogeochemical properties that can be used to predict the likely behavior (partitioning) of radionuclides from formations at depth: (1) Formations are generally ancient (fossil, > 100 million years old, particularly in the case of the Marcellus Shale), suggesting that radioactive decay products are present and in equilibrium with the supporting progenitor (37); (2) Formations are likely anoxic, reducing environments at depth (38). This has direct implications for the fate and transport of select redox-sensitive radionuclides (e.g., U, Po) and indirect implications by altering the key adsorptive surfaces (for instance, Mn and Fe minerals) (39-41); (3) At depth, microbial reduction of sulphate (SO4 2- ) to form sulfides (H2S, S 2- ) enhances the solubility of heavier alkaline earth metals (Sr, Ba, Ra). The implication is that in environments low in sulphates, there is a higher probability that Ra will be soluble (RaSO4 Ksp = 4.25 x )(42) as evidenced by low SO4 2- brines from the Marcellus Shale region having high levels of Ra isotopes (43-46); and (4) Interstitial fluids in some black shales (Marcellus Shale in particular) are likely high in salinity, which creates conditions that enhances the solubility of Ra (47,48). 5

25 1.5. Partitioning in the Subsurface Based on our investigations of NORM in Marcellus Shale produced fluids we developed a general model to predict partitioning of U-series and Th-series progenitors and radioactive progeny between solid-phase materials (bit cuttings; solid waste generated by drilling) and interstitial brine (flowback/produced fluids) extracted through the unconventional drilling/hydraulic fracturing process. To illustrate the principles of our generalized model, we describe the partitioning of the radionuclides in these series at depth by examining the physico-chemical events that govern the biogeochemical behavior of the radionuclides in these series. We begin with a single atom of apical progenitors 238 U and 232 Th, and examine differences in geochemistry and decay modes that govern the separation of progenitors and radioactive progeny (Figure 1.3) Uranium Series Partitioning at Depth Owing to the geologic history and chemically-reducing conditions of the Marcellus Shale, one can expect 238 U (t1/2 = 4.5 x 10 9 years) to be contained in the crystal lattice of minerals in a reduced-immobile (U +4 ) oxidation state (35). As 238 U decays by alpha-particle emission to 234 Th, it imparts a large amount of energy (often referred to as alpha recoil energy) to the Th nucleus. Alpha recoil energy is sufficient to break chemical bonds in the crystal structure of the rock (49), potentially leading to enrichment of the 234 Th atoms located at the solid-phase interstitial aqueous-brine interface (26,50). Although the geochemistry of Th is not susceptible to changes in oxygen concentration that might arise under environmental conditions, Th is known to be highly particle reactive. These properties predict Th to be relatively immobile via adsorption to mineral surfaces at depth in shale formations (51). Thus, the reducing environment of the Marcellus Shale and particle reactivity of Th predict that U and Th radionulclides are likely to be relatively immobile and unlikely to be extracted into aqueous-phase hydraulic fracturing fluids used for natural gas mining (34,52). Conversely, radioactive decay of solid-phase bound 230 Th results in 226 Ra species that are much more soluble in the interstitial brine due to low sulfate concentrations and high salinity of Marcellus Shale formation water. 6

26 The decay of 226 Ra leads to the formation of the radioactive noble gas 222 Rn, which adds complexity to predictions of the fate of successive decay products. Because 222 Rn is an inert gas with a half-life of nearly four days, gaseous diffusion and partitioning of 222 Rn (and its subsequent decay progeny) from 226 Ra via diffusion through fissures created by hydraulic fracturing events is possible (53). In general, 222 Rn only travels 0.1 m in wet soils by diffusion alone, but long-range transport is possible when coupled with a carrier fluid (54). Given that 222 Rn has increased solubility under high pressure at depth, it is likely that 222 Rn will be contained in the interstitial fluids of the formation only to decay through a series of short-lived isotopes to insoluble radioactive decay product 210 Pb (t1/2 = 22.2 years) (54). More research is needed to determine the effects of the divalent-rich saline environment on the solubility of 222 Rn (55). Careful sample preparation and measurements of flowback water and produced fluids from hydraulic fracturing at the time of extraction have the potential to elucidate more precisely the radioactive steady-state/non-steady-state relationship of 226 Ra and progeny 222 Rn in liquid waste products of unconventional drilling. Differences in the geochemistry of 210 Pb and 226 Ra have provided an opportunity to develop a temporal understanding of geochemical phenomena for decades (56). However, as 210 Pb decays to the redox active element, 210 Po, the fate of 226 Ra progeny becomes less clear. Studies of anoxic marine environments suggest that 210 Po can partition from 210 Pb and concentrate in organic rich particulate phases (57). Other studies show that under low-oxygen conditions, 210 Po is particle reactive and its transport is associated with the migration of Fe or Mn minerals (40,57-59). Although it is currently unknown whether reagents used in hydraulic fracturing fluids will mobilize 210 Po, its transport in the subsurface will likely be coupled with changes in redox conditions, ph, and bulk movement of Fe- and Mn-containing particulates. Given that 210 Po and 210 Pb can separate from one another under certain environmental conditions (60), researchers should measure 210 Pb and 210 Po independently. Use of 210 Po levels as a proxy for 210 Pb radioactivity concentrations may not be appropriate. The potentially high levels of 210 Po in unconventional drilling wastes present a unique opportunity to study fundamental 210 Po processes at depth and in the terrestrial environment. For example, future studies 7

27 could focus on the possible relationships between microorgamisms, sulfur-cycling, and polonium partitioning (61) Thorium Series Partitioning at Depth The fate and transport of the 232 Th series is similar to the previous discussion of the 238 U series. The progenitor radionuclide, 232 Th (t1/2 = 1.4 x years), is insoluble in environmental waters and brines. As 232 Th decays by alpha emission to 228 Ra (t1/2= 5.75 years), the resulting 228 Ra progeny is soluble in the sulphate-deficient, divalent-rich brine. As 228 Ra decays to 228 Ac (t1/2 = 6.15 hours) by beta emission, the fate is uncertain. Generally, Ac forms insoluble complexes and quickly adsorbs to mineral surfaces, but given its short half-life it can be difficult to discern the exact mechanism (62). Then 228 Ac decays by beta emission to the insoluble 228 Th (t1/2 = 1.91 years). Note, the large difference in solubility for 228 Ra and 228 Th gives rise to a chronometer (transient equilibrium model) that has potential to assist in determining the time when samples were removed from the Marcellus Shale (63). The nucleus then undergoes decay to form 224 Ra (t1/2 = 3.63 days), which again solubilizes into the brine. 220 Radon (t1/2 = 55.6 s) then decays by alpha emission to form 216 Po (t1/2 = s), which rapidly emits another alpha particle to form 212 Pb (t1/2 = hours). Similar to 210 Pb in the 238 U decay series, 212 Pb is expected to be insoluble and particle reactive. Next, 212 Pb decays by beta emission to 212 Bi (t1/2 = min), which is also likely insoluble (64). Then 212 Bi branches to two different decay products; 64% of decays are by beta emission to form the very short-lived 212 Po (t1/2 = μs) while the other 36% of decays form 208 Tl (t1/2 = min) (25). Both 212 Po and 208 Tl decay, by alpha and beta particle emissions respectively, to 208 Pb (stable) Radioactive Decay, Equilibrium, and Ingrowth This section describes the fundamental properties (decay, equilibrium, ingrowth) of radioactive materials and how these properties relate to unconventional drilling wastes in general Radioactive Decay Radioactivity (A) is a measurement of the number of decaying atoms in a sample in a given period of time. Radioactive decay of any given atom is a spontaneous event; 8

28 however, mathematical models can predict the decay rate of large groups of atoms (N) of the same isotope. It is observed that isotopes decay by first order kinetics at a rate related to their half-life (t1/2) according the following equations (eq.: 1-3):, eq. (1), eq. (2) eq. (3) Within the context of NORM, progenitor atoms decay by alpha particle (charged helium nucleus, 4 He 2+, α) or beta particle emissions (electron, β - ) to form progeny atoms. After one half-life, exactly 50% of the progenitor of radioactive atoms will exist. After two half-lives, exactly 25% of the progenitor atoms exist. After three half-lives, exactly 12.5% of the progenitor atoms remain. And the pattern continues, such that after every half-life, the continual radioactive decay results in exactly 50% of the remaining progenitor atoms having decayed by the time the next half-life begins. This concept is the foundation for describing the decay of a single radioactive element. However, when considering a radioactive decay series, the radioactive-progenitor atom decays to a radioactive-progeny atom, which in turn, decays to a radioactive-second-progeny atom. This pattern continues with progenitors providing the input of atoms to progeny and the progeny providing the input of atoms for successive progeny, until reaching a stable decay product. This relationship can be quantified by a differential equation described by Bateman in 1910 (65). 9

29 Radioactive Equilibrium For the purposes environmental monitoring, the concentration of progeny, second progeny, or atom further along in the decay series may be of more interest than the progenitor. For instance, the concentrations of 226 Rn (t1/2 = 1600 y), 222 Rn (t1/2 = d), 210 Pb (t1/2 = 22.2 y), 210 Pb (t1/2 = d) may be of greater interest in the natural gas industry than the progenitor, 238 U (t1/2 = 4.5 x 10 9 y). In a closed system that has not been disturbed for millions of years (such as in an ancient, fossil shale formation at depth) the radioactivity concentrations of 226 Ra and 222 Rn are in radioactive equilibrium (steady state) with the progenitor, 238 U, where the radioactivity associated with 226 Ra, 222 Rn and 238 U are equal. However, during an event where this closed system is disturbed (such as unconventional drilling to extract natural gas) the physicochemical differences of certain NORM can result in a radiochemical disequilibrium (non-steady state), where the subsequent progeny radioactivity concentrations are not equal to the progenitor. During a disequilibrium event, progeny may partition from progenitor atoms, as well as other progeny atoms further in the decay chain. For instance, 226 Ra experiences elevated solubility in shale formations in hydraulic fracturing flowback water, while its progeny ( 222 Rn, 210 Pb, 210 Po) and supporting atoms higher in the decay chain ( 238 U, 234 Th, 234 Pa, 234 U, 230 Th) remain insoluble, resulting in partitioning of 226 Ra from its progenitors and progeny (63). Given that the progenitors have been removed, the radioactivity of 226 Ra will decrease at the rate of its half-life (1600 y). Because 226 Ra is unsupported by its progenitor radionuclides, its decay can be modeled using the basic radioactive decay equation described above (eq. 2). However, the activities of the progeny (including 222 Rn, 210 Pb, 210 Po) will increase through a process known as radioactive ingrowth Radioactive Ingrowth Radioactive ingrowth is important to consider when estimating the long-term risks associated with radioactivity liberated by unconventional drilling (63). The most precise way to describe radioactive ingrowth is through derivations of the Bateman equation (eq. 6 & 7), yet in practice, there are two scenarios where simplification of the Bateman equation may prove useful: secular equilibrium and transient equilibrium. Secular 10

30 equilibrium refers to a closed-system scenario in which the half-life of a supporting isotope is much longer than the decay product (e.g., 226 Ra: t1/2 = 1600 y; and 222 Rn: t1/2 = d). Immediately after a partitioning event that results in disequilibrium, time (t0), the progeny ( 222 Rn) will begin to grow in at a rate determined by its own half-life until it equals the activity of the supporting atom ( 226 Ra). Note, the progeny will grow into equilibrium with the progenitor with an activity ratio of 1:1, but the atomic ratio will not be 1:1 as this ratio related to half-lives (eq. 4): When the activities of the two nuclides become equal, which occurs after approximately 6-10 half-lives of the progeny (e.g., ~30 days for 222 Rn and ~150 years for 210 Pb, Figure 1.4A, 1.4B ), the progeny is said to be in secular equilibrium with the progenitor (e.g., 226 Ra). This relationship can be modeled using a simplified secular equilibrium equation (eq. 5): In contrast, transient equilibrium refers to a scenario in which the half-life of the progenitor is only slightly greater than that of the decay product (e.g., 228 Ra, t1/2 = 5.75 y; and 228 Th, t1/2 = 1.91 y). In this case, as with secular equilibrium, immediately after a partitioning event that results in disequilibrium, time (t0), the progeny ( 228 Th) will begin 11

31 to grow in at a rate related to its own half-life. 21 However, the progenitor ( 228 Ra) in this case is decaying on a time scale of similar magnitude as the progeny, and although the activity of the progenitor is initially larger than the progeny ( 228 Th), over time the activity of the progeny will exceed the activity of the progenitor (Figure 1.4C). The significance of this phenomenon is that several years after disequilibrium occurs, the activity of 228 Ra will be less than the activity of its decay products ( 228 Th, 224 Ra, 212 Pb, 212 Bi in particular). Note, 228 Th ( 228 Th t1/2 >> 224 Ra t1/2) will then support subsequent progeny in the decay series (Figure 1.4D). This relationship between 228 Ra and 228 Th can be modeled using a simplified transient equilibrium equation (eq. 6): Although these simplifications may be useful to explore the relationship between any two isotopes in a series, they are limited when modeling the complete decay series is desired. For instance, if concentrations of 210 Pb and 210 Po (decay products of 238 U) or 228 Th and 224 Ra (decay products of 232 Th) are needed, then the Bateman equation must be used. The following equations (eq. 7 & 8) can provide the radioactivity concentrations of any decay product in any decay series using standard spreadsheet software: By assuming that the activities/atoms of decay products are zero at some starting time, (t0), one can easily model how long it will take each decay product to reach equilibrium with a progenitor. For example, when hydraulic fracturing flowback fluids are initially captured at the surface of the earth they are enriched in 226 Ra. Investigations 12

32 from our laboratory indicate that decay products may be absent from the flowback; however, given the nature of radioactive materials the decay products will ingrow. 63 By modeling 226 Ra-decay product ingrowth using the Bateman equation, we can show that 222 Rn activities steadily ingrow, approaching equilibrium in ~30 days (in a closed-system where 222 Rn cannot escape). The decay products of 222 Rn with short half-lives ( 218 Po, 214 Pb, 214 Bi, 214 Po) quickly follow the ingrowth of 222 Rn. The result is that the total radioactivity due to 226 Ra and its decay products will increase by a factor of approximately six in 30 days as the short-lived progeny approach secular equilibrium with 226 Ra (Figure 1.4E). Further, the total radioactivity will continue to increase for nearly 100 years as the long-lived 210 Pb grows into the sample (Figure 1.4F). The 210 Bi will relatively quickly establish equilibrium with 210 Pb since it has a relatively short halflife. The final radioactive decay product in the series 210 Po with a half-life of days takes approximately 3 years to reach equilibrium with 210 Pb and will then will continue to increase until establishing secular equilibrium with 226 Ra. Although this theoretical discussion of a closed-system is useful for illustrating how radioactivity behaves, closed-system models may not be suitable for environmental systems. Shale formations at depth likely behave as a closed-system, until disturbed by unconventional drilling. The drilling process is quite extensive and comprises multiple stages that generate, reuse, or dispose of large volumes of solid or liquid materials that open the system to different environmental conditions Major Stages of Unconventional Drilling Unconventional drilling can be broken down into six major stages, including: (1) water acquisition, (2) chemical mixing, (3) drilling, (4) injection of hydraulic fracturing fluids, (5) releasing well pressure (flowback/produced fluids and gas flaring), and (6) treatment or storage of liquid and solid wastes (Figure 1.5) (66). Each of these stages has distinct characteristics and environmental considerations that help determine which radionuclides to expect throughout the drilling process. 13

33 Water Acquisition One hallmark of unconventional drilling operations is the tremendous volume of water required (67,68). Some operations in the Marcellus Shale region (Eastern US) have been documented to use up to 40,000 m 3 of water for a single fracture (16). Unsurprisingly, the potential for straining fresh water resources is a concern, particularly at the local scale and in the arid Western US (69). In addition to these concerns, the cost of acquiring water has led many operators to pursue new wastewater purification technologies that allow for the reuse or recycling of flowback/produced fluids (70). One drawback with reusing such fluids is that flowback and produced fluids may be enriched in Ra isotopes (43,44). Although some of the treatment technologies may remove Ra isotopes, they may not simultaneously remove other NORM (71). For recycling technologies to effectively remove radioactivity from produced fluids, they must consider the nature of radioactive ingrowth. Undertreated/untreated recycled fluids may contain 228 Ra-decay products such as 228 Ac, 228 Th, 220 Rn, 212 Pb, 212 Bi, 208 Tl and 226 Ra-decay products such as 222 Rn, 214 Pb, 214 Bi, 210 Pb, and 210 Po Chemical Mixing A major source of controversy surrounding unconventional drilling in the United States is the large volume of unspecified chemicals used in hydraulic fracturing fluids (72). At the federal level in the United States, these chemicals and chemical blends have largely been exempted from disclosure due to trade secret protection (73). In recent years many companies have identified the majority of the chemicals, which are listed well-bywell in publicly accessible databases (for example, FracFocus.org) (74). Some of the disclosed constituents of fracturing fluids (including acids, reducing agents, organics, chelators) are known to interact with NORM (72). For example, uranium mobility is enhanced when complexed with citrates a known constituent of hydraulic fracturing fluids (75). Additionally, hydraulic fracturing fluids are acidified with hydrochloric acid (11), a reagent that is commonly used in laboratories to solubilize NORM. Without detailed information on the chemicals introduced to the formation, it is difficult to predict how NORM will interact when it comes in contact with hydraulic fracturing fluids. 14

34 Further, the complexity, quantity, and diversity of chemical blends used as hydraulic fracturing fluids suggest a case-by-case analysis of each well is necessary Drilling Drilling operators have used gamma-ray-log-detectors for decades to find target formations due to the well known correlation between gas productivity and radioactivity (76). Historically, natural gas wells were vertical (conventional well), and thus only a relatively small portion of the well was in the target formation of higher radioactivity. Advances in horizontal drilling now allow operators to drill down and laterally through the formation for thousands of meters (1). The result is significantly larger surface area of the unconventional well in the formation in comparison to conventional, vertical wells. In order to make space for the well, material must be removed from the depth. The material that is removed is referred to simply as cuttings, (77) or commonly as bit cuttings or drill cuttings. Although values vary from well-to-well, one report indicated a single horizontal well may produce 250,000 kg of bit cuttings (77). Since a large portion of these bit cuttings comes from the higher radioactivity formation, the bit cuttings can be expected to be enriched in radioactivity. A recent report indicates that radioactivity concentrations of 238 U in vertical cuttings were between 40 and 70 Bq/kg, whereas concentrations in horizontal cuttings exceeded 300 Bq/kg (78). Horizontal bit cuttings can similarly be expected to be enriched in insoluble U-series decay products, such as Pa, Th, Po, and Pb isotopes Injection Once the well has been drilled and the casing has been installed, hydraulic fracturing fluids are pumped into the well at tremendous pressures (up to 800 kpa) (11). In some cases industry will inject radioactive tracers into the well to check for inter-well connectivity or to measure flow rates (79). Most of the radioactive materials used at this stage are gamma-emitting radionuclides that decay to a stable product. Thus, the phenomenon of radioactive ingrowth that is observed for the natural decay chains is not observed; radioactivity associated with these tracers will decrease over time. Additionally, many of the tracers have relatively short half-lives (ex: 131 I t1/2= days) 15

35 and will consequently decay to stable decay products in a short period of time, unlike the natural decay chains which will produce radioactive decay products for millennia. The greatest potential for lasting radioactive contamination during the injection stage is in the event the high pressure causes the well casing to fail. The frequency of casing failure in unconventional gas wells, albeit debatable, is more likely than in conventional wells (80). Estimates of casement failure rates are quite variable with rates suggested from 1-2% to as high as 6.3% (11,81). If a casing failure were to occur, there is the potential for fluids from the well, containing NORM (from recycled fluids and interstitial fluids) or radioactive tracers, to leach into aquifers (82). Although this scenario is unlikely, there have been reports of signatures unique to the Marcellus Shale formation appearing in shallow domestic wells near hydraulic fracturing operations (83,84). To our knowledge, no comprehensive studies have been performed to identify levels of NORM present in groundwater around drilling operations. Due to the natural occurrence of NORM in most groundwater the impacts of drilling operations will be difficult to assess (85). Without a well-controlled, longitudinal study that has pre- and post- drilling data, conclusions may be prone to confirmation bias Flowback and Flaring After the well has been fractured, the pressure at the wellhead is lowered to allow gases and fluids to return to the surface. Initially, returned fluids, termed flowback, consist largely of the hydraulic fracturing fluids that were injected (11). Over time, the well will continue to release fluids, termed produced fluids. These fluids are typically much higher in total dissolved solids (TDS), salinity, and NORM (44,46). Over time, a well releases increasingly complex fluids that may be enriched in Ra isotopes naturally present in the fractured formation. Although Ra isotopes may be selectively solubilized in flowback/produced fluids, over time, 228 Ra-decay products such as 228 Ac, 228 Th, 220 Rn, 212 Pb, 212 Bi, 208 Tl and 226 Ra-decay products such as 222 Rn, 214 Pb, 214 Bi, 210 Pb, and 210 Po will ingrow (63). In addition to liquid wastes, natural gas wells produce large volumes of gaseous waste. This gaseous waste includes hydrogen sulfide, volatile organic compounds (VOCs), natural gas, and radioactive Rn gas (86). Flaring and/or venting are common and 16

36 necessary practices at natural gas extraction sites, for safety, environmental, and economic reasons (87). Although the extent to which flares reduce the environmental impact of produced gases is debatable (88), it will have no effect on the radioactivity of Rn gas. Surprisingly little attention has been paid to the extent/impacts of Rn gas during the flaring stage, even though Rn is a well-known contaminant of natural gas streams (89-91). One article has suggested that increased 222 Rn levels in natural gas extracted from shale will increase radioactivity concentrations in homes (from use of stoves and space heaters) in New York State, resulting in an additional 1,182-30,448 lung cancers (92). More data on the levels of 222 Rn in natural gas streams at the source and end-point are needed to validate this assessment. Very little is known about the levels Rn on drilling sites, though a recent report indicates that levels of 222 Rn on Marcellus Shale drilling sites are in the range of ambient background 222 Rn concentrations in the US (7-26 Bq/m 3 )(78). As studies are designed to address radiological exposures associated with 222 Rn, both on drilling sites and downstream, careful consideration of 222 Rn decay products is needed. The long-lived progeny of 222 Rn, 210 Pb and 210 Po, can adsorb to dusts and accumulate into higher organisms (93-96) Treatment The final stage of unconventional drilling is treatment of solid and liquid wastes. Little peer-reviewed information is available about the composition of NORM in wastes from the Marcellus Shale region and their potential to migrate into the environment (15). To date, reports on NORM associated with unconventional drilling have largely focused on three components of the radioactivity: gross alpha/beta levels (97), analysis of Ra levels (43,44,98-100), and gamma spectrometry (101). Gross alpha/beta levels are a simple screening technique for radioactivity in environmental samples (102,103), but they do not indicate which radionuclides are present in the waste. Thus, it is not feasible to determine whether the level of radioactivity will increase, persist, or decrease over time without subsequent analyses. Analysis of Ra levels in flowback and produced fluids liquid waste from Marcellus Shale unconventional drilling has proven challenging, and can be underestimated (in some cases > 100 fold) due to matrix interferences (43). Traditional drinking water methods and other wet chemistry methods for Ra isotopes do not work on the complex brines from the oil and gas fields (43). Methods such as gamma 17

37 spectroscopy or radon emanation are superior for these samples as they are less affected by matrix composition (43). However, analysis of Ra isotopes alone does not provide information on the total radioactivity, which can increase substantially for over 100 years resulting from the ingrowth of the radiogenic progeny (63). Gamma spectroscopy is used to measure select gamma-emitting radionuclides in the natural decay series (63,101). In some cases, measurements of gamma-emitters can be used to infer radioactivity concentrations of radionuclides that are not gamma-emitters (example, gamma emissions from 228 Ac can be used to infer 228 Ra levels). However, due to partitioning events in the subsurface, analysts cannot assume all radionuclides will be in equilibrium (example, 228 Ac levels cannot be used to infer levels of its decay product 228 Th) (63,85). Gamma spectrometry alone cannot fully characterize the levels of NORM present, particularly with respect to Ra decay products ( 228 Th, 222 Rn, 210 Pb and 210 Po). Without comprehensive analyses of NORM in these wastes (i.e. gamma spectrometry and alpha spectrometry), the levels of exposure will remain relatively unknown. Most environmental monitoring reports of Marcellus Shale waste have focused on 226 Ra associated with liquid waste (i.e. flowback and produced fluids) and dose rates from solid waste (i.e. bit cuttings and drill cuttings) (43,44,46,63,98,104) Liquid Waste In the US, oil and gas operations are exempt from many federal environmental protection regulations, such as the Safe Drinking Water Act (the so-called Halliburton Loophole ) (105). Further, the levels of NORM in oil and gas wastes are not regulated at the federal level, but rather at the state level (106). Thus, treatment options for liquid wastes differ from state-to-state due to a combination of regulations, economics, and local geology (107). The major treatment options in the US for liquid wastes from unconventional drilling are: (1) direct discharge (i.e. spraying on roads) (2) chemical treatment at wastewater treatment plants, (3) deep surface injection, and (4) recycling (77). The Marcellus Shale region provides an interesting case study on how state regulations can affect the handling of liquid wastes. In Pennsylvania in particular, radioactivity in liquid wastes has proven to be a controversial issue (15). Since 18

38 unconventional gas exploration and production in the Marcellus Shale region began in 2003 (76), there was a rapid surge in drilling and waste generation across the region (107). In 2014, for example, over 8000 active wells generated an estimated 5 billion liters of flowback and produced fluids (107). Liquid wastes in Pennsylvania are largely disposed of at wastewater treatment plants as there are no suitable deep-well injection sites (107). This practice has resulted in cases of contaminated sediments downstream from these facilities (78,98). Despite high profile publications on Ra contamination from untreated or undertreated flowback and produced fluids, a recent report from the State of Pennsylvania indicates that waste treatment facilities are still poorly equipped to remove Ra from unconventional drilling wastes (78). However, it is important to note that many drilling operators in the Marcellus Shale region are moving towards flowback recycling practices (70,108). As liquid waste management continues to shift towards recycling, the volume of produced liquid waste containing Ra to be treated and disposed at the surface will decrease. Radium isotopes appear to be liberated from the Marcellus Shale and soluble in the liquid waste (44,46,63), which is consistent with historical observations of disequilibrium in oil and natural gas brines from conventional operations (109). Two major complications with handling these wastes are (1) the large volume of brines produced (>5 billion liters in 2014 in PA alone) (107), and (2) the high levels of dissolved solids and divalent cations (Sr, Ca, Ba) present in the liquids, which can interfere with treatment processes aimed at removing Ra (67). When wastewater treatment plants are not equipped to handle these high levels of divalent cations, flowback and produced fluids wastes may flow through the wastewater treatment plant untreated or undertreated (98, ). Discharges of undertreated waste may result in the accumulation of these divalent cations in sediments of riparian environments (98). This was recently evidenced by a report, in which the investigators documented that levels of 226 Ra and 228 Ra in sediments immediately downstream of the Josephine Wastewater Treatment Facility in Pennsylvania, USA, were several orders of magnitude higher than background levels upstream of the facility (98). Due to the high levels of Ra isotopes, the plant operator now plans to dredge the contaminated sediments(113). Other waste operators in Pennsylvania have experienced similar challenges in removing Ra 19

39 from complex hydraulic fracturing wastes (78,114). In response to these challenges, several groups have suggested mixing in high-sulphate coal mine drainage as an approach to precipitate Ba and Ra isotopes as insoluble sulphate complexes from the liquid waste of the Marcellus Shale (115,116) Solid Waste There are numerous methods available for the disposal and treatment of solid wastes generated in the drilling process, including biological and non-biological treatments (117). In some states, solid waste is disposed of in landfills, though in other states, like Oklahoma, bit cuttings and drilling muds are tilled into agricultural soils (77,118). Given the mass of solid waste generated by unconventional drilling (up to 250,000 kg / well) (77), there is surprisingly little information available on their radioactivity content. Most readily available information available arises from newspaper reports of trucks turned away from landfills after tripping radiation alarms. For example, one truck carrying Marcellus Shale bit cuttings was turned away from a Pennsylvania landfill, because the radioactive emissions from the load exceeded the allowable radiation threshold. The dose rate from these bit cuttings was measured at 0.96 μs/hr, which exceeded the Pennsylvania threshold of 0.5 μs/hr (104,119). In another case at the Meadowfill Landfill in West Virginia, a truck was turned away when bit cuttings measured 2.12 μs/hr, exceeding the allowable limit of 1.5 μs/hr (120). While these events of solid waste exceeding the allowable dose thresholds invariably raise criticism and concern from citizens, the risk of radiation exposure (including Rn) to the general public is likely minimal (78,121). Although assessments of radioactivity dose rates are useful from a health physicist s perspective, dose rates provide little information about the elemental and isotopic composition of these materials. Only recently has limited information about the composition ( nat U, 232 Th, 228 Ra, and 226 Ra levels) of the bit cuttings become available from a report by the State of Pennsylvania (78). More detailed radiochemical assessments of the elemental and isotopic composition are critical to determine the equilibrium status, ingrowth potential, and likelihood for NORM to migrate into the surrounding environment. 20

40 1.10. Research Needs There are many important research questions concerning NORM that have recently surfaced as unconventional drilling expands around the world. Three unanswered questions in the context of environmental radiochemistry are: (1) the fate and transport of 226 Ra decay products in freshwater environments, (2) the behavior and composition of NORM in solid waste from NORM-enriched shale formations, and (3) regional impacts of 222 Rn gas released from 226 Ra containing wastes, flares, and natural gas streams Fate and Transport of 226 Ra-decay Products in Aqueous Environments As mentioned earlier, Ra from unconventional drilling waste can enter riparian environments (98). This observation has raised numerous questions about the fate and transport of Ra and methods to remove it from complex liquid wastes produced by unconventional drilling (115,116,122); however little research has been performed on Ra decay products. Due to radioactive ingrowth processes, wastes that contain natural Ra isotopes ( 228 Ra, 226 Ra, 224 Ra, and 223 Ra) will generate Ra decay products. Importantly, because Ra decay products have different physicochemical properties than Ra, methods that are designed to remove Ra from liquid wastes will not necessarily remove Ra decay products. The three Ra decay products of greatest interest are: 222 Rn, 210 Pb, and 210 Po, because these isotopes possess radiochemical (sufficiently long half-lives) and physicochemical (unique chemistry from the supporting 226 Ra) properties that allow for partitioning in the environment and possible bioaccumulation in higher organisms (94,95,123). On-going studies in fresh waters in West Virginia by our laboratory indicate that Ra decay products have accumulated in sediments to a level nearly five times that of 226 Ra (Figure 1.6) (124). The mechanism of 210 Pb and 210 Po enrichment in sediments is still under investigation. One possibility is that 226 Ra is more soluble in this environmental system and is constantly removed from the system, but steady inputs of 210 Pb and 210 Po into the lake readily accumulate onto mineral surfaces in lake sediments. Currently, we are investigating the role of seasonal fluctuations in the observed disequilibrium. Alternatively, dissolved 222 Rn may be transported in effluent discharge pipes as the result 21

41 of 226 Ra scale formation (125). A steady stream of 222 Rn could result in the enrichment of 222 Rn-decay products, including 210 Pb and 210 Po, in water columns and sediments of seasonally anoxic lakes (126,127). Previous research indicates that excess 210 Po (disequilibrium with 210 Pb) is likely to occur in the summer in anoxic lake bottoms as Fe and Mn minerals are reduced to soluble phases (126). Further studies on 210 Pb and 210 Po levels are needed to elucidate their speciation, potential for migration, and exposure risks Behavior and Composition of NORM in Solid Waste To date, there have been no peer-reviewed scientific investigations on the radiochemistry of unconventional drilling solid waste. Numerous questions beckon, such as how redox sensitive elements (U, Fe, Mn, etc.) will behave when removed from depth, and how alteration of redox sensitive elements will affect the mobility of NORM. For example, as described earlier, U was trapped in shale formations in its reduced, immobile, +4 oxidation state. When brought to the surface, bit cuttings will be exposed to an oxidizing environment, which will likely result in the oxidization of U 4+ to hexavalent UO2 2+ (Figure 1.7) (128). Once in the 6+ oxidation state, U may more readily leach off of bit cuttings into the surrounding environment (129). It is difficult to assess the extent and rate of U oxidation as well as the potential for U 6+ to leach from bit cuttings without more data. Though, some lessons may be gleaned from the American West, where U mine tailings were stored along the banks of the Colorado River (130). Oxidized U 6+ from these tailings traveled into ground water, prompting years of research and attempts to reduce the mobile U to the immobile, U 4+ with bioremediation (131). In areas, such as Oklahoma, where bit cuttings and drilling muds are directly applied to fields, we expect a similar fate of U as described in mine tailings from CO. In other regions where bit cuttings are stored in landfills, such as the Marcellus Shale, we suspect that leachates will contain measurable quantities of U though the risk to the public is likely minimal (78). Non-radioactive, redox sensitive elements are also important to consider in assessing the fate and transport of NORM. Further research is needed to investigate the potential for 222 Rn, 210 Pb, and 210 Po to migrate through the environment. As an aside, measurements of 238 U are sometimes performed by mass spectrometry. Yet, given the alpha recoil enrichment processes that we described above, 22

42 234 U will likely not be in secular equilibrium with 238 U. As a result, determining 238 U activity by its mass and applying the assumption that 234 U activity is equivalent could underestimate the true radioactivity attributed to U isotopes (85). Furthermore, activity ratios of 234 U/ 238 U may provide valuable information for predicting NORM migration at contaminated sites (132). Thus, we recommend that when possible, isotopic nat U levels be measured by alpha spectrometry or another suitable method (63) Potential Regional Impacts of 222 Rn 226 Ra sources constantly produce 222 Rn gas. Considering that liquid waste from the natural gas industry is known to contain enriched levels of 226 Ra, very little attention has been given to 222 Rn. Researchers have known that 222 Rn is present in natural gas, though it is currently unclear what levels are present in shale gas and whether these levels pose a hazard (92,133,134). Although a recent report from the State of Pennsylvania indicates levels of 222 Rn are low in commercial gas, the levels of 222 Rn released during fugitive gas emissions and flaring of unwanted gases were not investigated (78). Since 222 Rn is not combustible, flaring will not remove its radiologic hazards. Once delivered to the atmosphere, 222 Rn will form decay products, which are known to fallout in particulates and in precipitation (Figure 1.8) (135,136). The progeny of 222 Rn, such as 210 Pb and 210 Po, could then be taken up by plants (such as tobacco), accumulate in lake bottom sediments, and ultimately organisms in the region (126,137). We suspect any increases in 222 Rn levels and 222 Rn products ( 210 Pb and 210 Po) will require well-controlled longitudinal studies, as many drilling operations occur in areas with relatively high levels of background 222 Rn (138) Conclusion NORM is a well-documented contaminant of conventional oil and natural gas equipment and wastes. Many of the challenges associated with NORM management in conventional wastes apply to the management of unconventional drilling wastes. The complexity and scale of wastes produced by unconventional drilling have proven difficult to handle in even the most developed of nations with decades of experience in natural gas production. When waste management protocols are inadequate, enriched levels of NORM from unconventional drilling activities can enter the environment. Most attention to date 23

43 with respect to NORM in unconventional drilling waste has focused on the risks of Ra isotopes entering aqueous environments. Given the natural ingrowth processes of radioactive decay products, wastes that are enriched in Ra isotopes will either contain Ra decay products or produce Ra decay products. Thus, studies on the fate and transport of NORM liberated by unconventional drilling operations should include Ra decay products. Similarly, studies of solid waste should include progenitors of Ra isotopes. NORM is comprised of multiple elements and isotopes of different physicochemical and radiochemical properties that play a role in environmental partitioning and any potential human exposure. Further studies are needed to characterize NORM solid, liquid, and gaseous wastes generated by unconventional drilling operations Addendum: Basic Properties of NORM Uranium Although uses of uranium (U, [Rn]5f36d17s2) date back to 79 CE, when the Romans used U to add yellow to ceramic glazes, the discovery is credited to a German chemist, Martin Heinrich Klaproth, in 1789 (52,139). Klaproth dissolved pitchblende in nitric acid then neutralized the solution with NaOH and precipitated yellow sodium diuranate and concluded this was a new element. He later named the new element after Uranus, the primordial Greek god of sky, because of its yellow colour and the recent discovery of the planet Uranus eight years earlier (139). There are three naturally occurring isotopes of U, 238 U (t1/2= 4.468x10 9 years, α), 235 U (t1/2= 7.04x10 8 years, α), and 234 U (t1/2= 2.455x10 5 years, α) (25,140). The behavior of U in the environment is greatly dependent on the redox conditions. While in U 6+ (as UO2 2+ ) is the most stable cation in oxidizing conditions, it is readily reduced to U 4+ in anoxic conditions. In general, U forms strong inorganic and organic complexes, but the strength of the species depends on the oxidation state (26). U 4+ : F - > PO4 2- > SCN - >NO3 - > Cl - UO2 2+ : CO3 2- > PO4 2- > SO4 2- In the case of Marcellus Shale, the formation is rich in U due to the accumulating U 6+ -carbonate (UO2CO3) species from the ancient ocean (35,141). Now, the conditions are very reducing, immobilizing U and reducing it to U 4+, therefore, U will be recovered 24

44 with the bit cuttings. Once U is exposed to ambient conditions, it will be oxidized to U 6+ and will be soluble Protactinium Protactinium (Pa, [Rn]5f 2 6d 1 7s 2 ) was first isolated by William Crooks in 1900 when he dissolved uranyl nitrate in ether but he was unable to characterize it as a new element, so he named it uranium-x (142). In 1913, Fajans and Göhring fully characterized uranium-x as new element and named it brevium because of the short halflife of 234m Pa (142). Finally in 1917, a German group (Hahn and Meitner) and a British group (Soddy and Crankston) independently discovered another isotope of Pa with a longer half-life and named it proto-actinium (later changed by IUPAC to protactinium), because it was the progenitor of actinium (4). There are two naturally occurring radionuclides of Pa, 234 Pa (t1/2= 6.7 hours, β - ) and 231 Pa (t1/2= 32,760 years, α). 26, 143 In general, Pa exists as a pentavalent cation and forms strong affinity for inorganic complexing ligands: F - > SO4 2- >> NO3 - > Cl - > ClO4 - In the environment, Pa is known to readily hydrolyze to form insoluble colloidal species, but in the presence of a high concentration of strong inorganic ligands, Pa may remain soluble (26,142). In the conditions such as the Marcellus Shale, it is likely that Pa will be largely insoluble due lack of strong complexing ligands (i.e. F - and SO4 2- ), and would be potentially recoverable in the bit cuttings Thorium Thorium (Th, [Rn] 6d 2 7s 2 ) was first documented in 1823 in Norway. Morten Thrane Esmark found a black mineral on the island of Løvøya and presented it to his father, mineralogist Jens Esmark, and he could not identify the sample (144). Jens Esmark sent the sample to a Swedish chemist, Jöns Jakob Berzelius, who in 1828, concluded it was a new element and named it after Thor, the Norse god of thunder (144). There are six naturally occurring isotopes of Th, 234 Th (t1/2= 27.1 days, β - ) 232 Th (t1/2= 1.4x10 10 years, α), 231 Th (t1/2= hours, β - ), 230 Th (t1/2= 75,400 years, α), 228 Th (t1/2= years, α), and 227 Th (t1/2= days, α) (26,145). Generally, Th exists as a tetravalent actinide and is redox inactive in the environment. Because Th 4+ is the 25

45 dominant species, Th remains largely insoluble and but its mobility is greatly controlled by the ability to form complexes with organic and inorganic ligands: F - > PO4 2- > SCN - >NO3 - > Cl - While Th remains insoluble, it can coordinate strongly with particles in the environment and be mobilized by their transportation (26). In the Marcellus shale, Th will remain insoluble and be recoverable with the bit cuttings. However, 228 Th, originating from 228 Ra, will grow into secular equilibrium in the recover fluids Actinium Actinium (Ac, [Rn] 6d 1 7s 2 ) was discovered in 1899 by a French chemist, named André-Louis Debierne, when he isolated it from pitchblende residues of Marie and Pierre Curie radium extraction. The name originates from the Greek word aktis, meaning beam or light, because of the eerie blue glow of Cerenkov radiation emitted from actinium (146). There are two naturally occurring isotopes of Ac, 228 Ac (t1/2= 6.15 h, β - ) and 227 Ac (t1/2= years, β - )(26). Chemically, Ac behaves as a trivalent cation similar to the lanthanide elements, remaining mostly insoluble and ph inactive (146). Within the conditions in the Marcellus Shale, Ac will remain largely insoluble and is expected to be associated with solid/particulate phases. However, 228 Ac, originating from 228 Ra, will grow into secular equilibrium in the recovered fluids Radium Radium (Ra, [Rn]7s 2 ) was first discovered by Marie and Pierre Curie in 1898 in the form of radium chloride by extraction from pitchblende (21). The name radium originates from the Latin word radius, meaning ray, referring to radium s intense production of energy rays (147). There are three common naturally occurring isotopes. 224 Ra (t1/2 = 3.66 d) and 228 Ra (t1/2 = 5.76 y) are found in the 232 Th decay series; 226 Ra (t1/2 = 1599 y) is found in the 238 U decay series. Ra is not redox sensitive and is found in the +2 oxidation state in nature (42). Owing to its highly basic behavior, Ra is not easily complexed. Ra does however form simple ionic salts. Radium sulphate and Ra carbonate are very insoluble, while Ra hydroxide, chloride, bromide, and nitrate are all soluble (42). Radium tends to precipitate (and coprecipitate) with all barium, most strontium, and most lead compounds as ionic salts. Due to the low sulphate concentrations in the Marcellus 26

46 Shale, Ra isotopes are expected to remain soluble in interstitial fluids, flowback, and produced fluids Radon Radon (Rn, [Xe]4f 14 5d 10 6s 2 6p 6 ) was discovered in 1900 by Dorn, who called it radium emanation (139). Yet, since 1923 the element has been known as radon. Each of the primordial decay series includes an isotope of Rn: 219 Rn (t1/2 = 3.96 s, sometimes referred to as actinon) belongs to the actinium series, 220 Rn (t1/2= 55.6 s, sometimes referred to as thoron) belongs to the thorium series, and 222 Rn (t1/2= days, commonly referred to as simply as radon). Radon is the heaviest noble gas, and is thus relatively chemical inert. Rn is relatively soluble in water, though the effects of high saline environments may significantly alter its partitioning between various phases in the subsurface (55). In the subsurface Rn is expected in brines (supported and unsupported) (148), organic layers (149), and in natural gas streams (89). Although Rn is relatively soluble in aqueous solutions, when liquids containing Rn are exposed to the atmosphere (open system) Rn gas will partition into the air as predicted by Henry s Law. Furthermore, solids containing 226 Ra will produce 222 Rn (150) Polonium Polonium (Po,[Xe]4f 14 5d 10 6s 2 6p 4 ) historically referred to as Radium F, was the first element discovered by Madame Marie Curie during her investigations of pitchblende (139). Polonium was named after Poland, the home country of Marie Curie. It is one of the rarest elements, with natural abundances of only 100 μg of 210 Po per ton of uranium ores (151). Investigations of the speciation and chemistry of Po is difficult as all known isotopes and isomers are radioactive. Furthermore, analysis of its chemistry is complicated by its volatility at temperatures over 100 C, Po is volatized, thus preventing the use of high temperature environmental sample preparations (152). There are several naturally-occurring Po isotopes, most of which have extremely short halflives: 218 Po (t1/2 = min), 216 Po (t1/2 = sec), 215 Po (t1/2 = x 10-3 sec), 214 Po (t1/2 = x 10-6 sec), 212 Po (t1/2 = x 10-6 sec), and 211 Po (t1/2 = sec). The longest-lived naturally-occurring Po isotope is 210 Po (t1/2 = days). Po is theorized to form the -2, +2, +4, and +6 valence states (151), though the environmentally relevant 27

47 valence states are likely +2 and +4 (153). Po is readily dissolved in dilute acids, but can be easily concentrated on manganese oxides or iron hydroxide surfaces even in complex samples. Interestingly, some investigators have discovered that only a portion of total Po is extracted by iron hydroxides, suggesting that multiple valence states and species of Po may coexist under certain conditions (61). Po is an elusive element that often behaves in unexpected ways; however, under the strong reducing conditions of shale formations it is expected that Po will be particle reactive and mostly associated with bit cuttings/drill cuttings. Importantly, Po isotopes will ingrow into phases that contain either supporting Ra or Rn isotopes. We believe the environmental transport mechanism and ultimate fate of 210 Po (and its progenitor, 210 Pb) liberated by unconventional drilling will be one of the most interesting and challenging research questions in the coming years Bismuth Bismuth (Bi, [Xe] 4f 14 5d 10 6s 2 6p 3 ) was first discovered in the 15 th century and identified as a distinct element by Potts and Bergmann in 1739 (154). The name bismuth originates from the German words, weisse masse, meaning white mass. For centuries, Bi was confused with Pb. 139 There are several naturally-occurring radioactive isotopes including: 215 Bi (t1/2 = 7.6 min), 214 Bi (t1/2 = 19.9 min), 212 Bi, (t1/2 = min), 211 Bi (t1/2 = 2.14 min), and 210 Bi (t1/2 = day). Until recently, 209 Bi was thought to be the heaviest stable isotope; however, new evidence suggests that this isotope emits lowenergy α-particles with an extremely long half-live (t1/2 = 1.9 x year) (155). Bi is most commonly found in the +3 and +5 oxidation states and tends to form insoluble complexes (64,139). Given this tendency, Bi is expected to adsorb to particulate and mineral phases. In practice 214 Bi and 212 Bi are important gamma emitting isotopes for determining levels of supporting Ra isotopes (156) Lead Lead (Pb, [Xe] 4f14 5d10 6s2 6p2) has been in common use for thousands of years and is renowned for its toxicity. 139 The word lead has Anglo-Saxon roots, yet the abbreviation Pb is derived from the Latin word plumbum. Radioactive Pb has numerous applications in radiochemistry, geology, and medicine. Naturally-occurring radioisotopes of Pb include: 214 Pb (t1/2 = 26.8 min), 212 Pb (t1/2 = hour), 211 Pb (t1/2 = 36.1 min), 28

48 and 210 Pb (t1/2 = 22.2 year). The 238 U, 235 U, and 232 Th decay series all decay to a stable Pb isotope ( 206 Pb, 207 Pb, and 208 Pb, respectively). Pb exhibits two oxidation states in solutions, the +4 oxidation state, or more commonly the +2 state (157). Pb is insoluble when complexed with halides, sulphates, carbonates, phosphates, and sulphides, but soluble when complexed with nitrates, nitrites, citrates or acetates (157). In the environment, Pb tends to be relatively immobile, thus making it a useful pollution indicator (158). 214 Pb and 212 Pb are important isotopes for determining gamma emissions of supporting Ra isotopes (156). Due to (1) the difficulty in measuring 210 Pb in comparison to other gamma-emitting NORM, and (2) the natural ingrowth of 210 Pb from 226 Ra source, we believe the fate and transport of 210 Pb associated with unconventional drilling wastes is one of the most interesting and challenging areas of environmental radiochemistry research Thallium Thallium (Tl, [Xe] 4f 14 5d 10 6s 2 6p 1 ) was discovered independently by Lamy and Crookes in 1861 (159). The name thallium is derived from the Greek word thallos, meaning green shoot in reference to the green light it emits in spectrometers (139). There are two relevant radioactive isotopes of Tl: 208 Tl (t1/2 = min) of the 232 Th series and 207 Tl (t1/2 = 4.77 min) of the 235 U series. Thallium has two observationally stable isotopes; 203 Tl and 205 Tl. Tl is most commonly found in a +1 or +3 oxidation state as ionic salts. In the +1 state Tl behaves similarly to potassium (K), which in part explains its chemical toxicity. In reducing environments, Tl is expected in the +3 state, where it behaves similarly to aluminium (III, Al) (159). Tl is commonly soluble, even in the carbonate form, but can be precipitated as a +1 ion with hydrogen sulfide, potassium chromate, potassium iodide or thionalide. Co-precipitation of thallium (III) in small amounts is possible with iron (III) hydroxide. Given the low atomic abundances and short half-lives of 207 Tl and 208 Tl, their potential to partition likely plays a minimal role in the gross transport of NORM from unconventional drilling wastes through the environment. In practice, the reliable gamma emissions from 208 Tl are important for monitoring 224 Ra and associated progeny. 29

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66 Figure 1-1 The primordial decay series of interest in shale formations: actinium ( 235 U) series (left), uranium ( 238 U) series (middle), and thorium ( 232 Th) series (right). All half-lives are from the National Nuclear Data Center (NuDat). 47

67 Figure 1-2 Uranium (U) trapped in marine organisms and sediments as an explanation for the increased levels of U and U decay products in marine black shale formations. 48

68 Figure 1-3 Theoretical partitioning model of U and U decay products at depth in shale formations (Adapted with permission from reference 63). 49

69 Figure 1-4 Equilibrium characteristics of selected NORM after a disequilibrium event as modeled by the Bateman equation. (A) 222 Rn grows into secular equilibrium with 226 Ra in less than 30 days. (B) 210 Pb grows into secular equilibrium with 226 Ra after 100 years. (C) 228 Th establishes transient equilibrium with 228 Ra. (D) 224 Ra approaches secular equilibrium with 228 Th. (E) 226 Ra decay products increase total radioactivity approximately 6-fold within 30 days. (F) Activity of 226 Ra decay products increase for more than 100 years formations (Adapted with permission from reference

70 Figure 1-5 Major stages of unconventional drilling as they relate to environmental radiochemistry. 51

71 Figure 1-6 Anticipated fates for 226 Ra and 226 Ra decay products in fresh water environments. 52

72 Figure 1-7 Oxidation of bit cuttings and other solid wastes may mobilize U and other NORM into ground water and other water resources. formations (Adapted with permission from reference 63). 53

73 Figure 1-8 Flaring of unwanted gases may result in regional increases of 222 Rn-decay product fallout. (Adapted with permission from reference 63). 54

74 Table 1-1 Naturally Occurring Radioactive Materials of Interest in Unconventional Drilling Wastes. Element Uranium (U) Expected forms Isotopes α/β/γ a Half-life S/L/G b Isotopic Detection c U 4+ reduced, particle reactive, expected in shale formation; U 6+ oxidized, mobile, expected to form under some conditions at the surface of the earth 238 d α 4.468x10 9 y S MS, AS, HPGe ( 234 Th, 234m Pa) 235 α, γ 7.04x10 8 y S MS, AS, HPGe 234 d α 2.455x10 5 y S MS, AS Protactinum (Pa) Pa 5+ particle reactive 234 m γ m S HPGe 234 β 6.7 h S HPGe ( 234m Pa) Thorium (Th) Th 4+ particle reactive 234 β, γ 27.1 d S MS, HPGe 232 α 1.4x10 10 y S MS, AS 230 α 75,400 y S MS, AS 228 d α y S AS Actinium (Ac) Ac 3+ particle reactive 228 β, γ 6.15 h S/L HPGe Radium (Ra) Ra 2+ soluble at depth 228 d β 5.75 d S/L HPGe ( 228 Ac) and surface, solubility 226 d α, γ 1600 y S/L HPGe (direct or 214 Bi, dependent on salinity 214 Pb) and chemical matrix 224 d α, γ d S/L HPGe (direct or 212 Bi, Pb) Radon (Rn) Rn, noble gas 222 d α d S/L/G Emanation 220 α 55.6 s S/L Emanation Polonium (Po) Po 2+, Po 4+ unclear which form, particle reactive 218 α m S/L/G N/A 216 α s S/L N/A 214 α 164.3x10-6 s S/L/G N/A 212 α x 10-6 s S/L N/A 210 d α d S/L/G AS Bismuth (Bi) Bi 3+ particle reactive 214 β, γ 19.9 m S/L/G HPGe 212 β, γ m S/L HPGe, AS 210 β d S/L/G N/A Lead (Pb) Pb 2+ particle reactive 214 β, γ 26.8 m S/L/G HPGe 212 β, γ h S/L HPGe 210 d β, γ 22.2 y S/L/G HPGe a (α) alpha-emitter; (β) beta-emitter; (γ) gamma-emitter b (S) expected to be present and/or generated in solid wastes (bit cuttings); (L) expected to be present and/or generated in liquid wastes (flowback/produced fluids); (G) expected to be present and/or generated gas streams (flaredwaste gases and natural gas) c (MS) mass-spectrometry; (AS)alpha-spectrometry; (HPGe) high purity germanium gamma-spectrometry Emanation radon emanation d key isotopes of interest in environmental fate and transport 55

75 CHAPTER 2: MONITORING RADIONUCLIDES IN SUBSURFACE DRINKING WATER SOURCES NEAR UNCONVENTIONAL DRILLING OPERATIONS: A PILOT STUDY This chapter was accepted for publication on 6 January, 2015, published online 23 January, 2015, and available in print April, This chapter is reprinted with permission. Please refer to: Nelson, A. W.; Knight, A. W.; Eitrheim, E. S.; Schultz, M., Monitoring radionuclides in subsurface drinking water sources near unconventional drilling operations: a pilot study. J. Environ. Radioact. 2015, 142, Abstract Unconventional drilling (the combination of hydraulic fracturing and horizontal drilling) to extract oil and natural gas is expanding rapidly around the world. The rate of expansion challenges scientists and regulators to assess the risks of the new technologies on drinking water resources. One concern is the potential for subsurface drinking water resource contamination by naturally occurring radioactive materials co-extracted during unconventional drilling activities. Given the rate of expansion, opportunities to test drinking water resources in the pre- and post-fracturing setting are rare. This pilot study investigated the levels of natural uranium, lead-210, and polonium-210 in private drinking wells within 2000 m of a large-volume hydraulic fracturing operation before and approximately one-year following the fracturing activities. Observed radionuclide concentrations in well waters tested did not exceed maximum contaminant levels recommended by state and federal agencies. No statistically-significant differences in radionuclide concentrations were observed in well-water samples collected before and after the hydraulic fracturing activities. Expanded monitoring of private drinking wells before and after hydraulic fracturing activities is needed to develop understanding of the potential for drinking water resource contamination from unconventional drilling and gas extraction activities Introduction The application of unconventional drilling (i.e., the combination of hydraulic fracturing and horizontal drilling) techniques to extract natural gas and oil is rapidly 56

76 expanding throughout the world (1, 2). Although the current political and economic landscape is favorable for expanded natural gas exploration, many have voiced concerns for potential environmental and public health impacts (3-5). One of the most important issues to be considered is the impact of unconventional drilling on local and regional water resources (6,7). Within this context, concern about potential contamination of drinking water resources by naturally occurring radioactive materials (NORM) liberated by unconventional drilling activities is on the rise (8). Emerging reports indicate that unconventional drilling activities may contaminate ground water, as evidenced by increased levels of methane gas and other geologic signatures apparently originating from the natural gas-bearing formations (9,10). Similarly, NORM have the potential to contaminate ground water by numerous mechanisms, including, but not limited to: flowback water spills on the surface, leakage of flowback from containment ponds, well casing failure, and introduction of new/larger fractures to the subsurface (11). Through any of these processes, NORM contained either within the formation or in wastes removed from the formation (bit cuttings, brine, gas streams), have the potential to partition into groundwater. The potential for migration through the formation depends on the physical-geochemical (redox state, ph sensitivity, gas/solid) and radiochemical properties (half-life, decay products) (12). Studying the impacts of unconventional drilling on NORM levels in private drinking is challenging for several reasons. In the United States (US), landowners are not required to monitor private drinking water wells for radionuclides (13). Consequently, there are no large publically-accessible databases of NORM levels in private drinking wells in regions with drilling activities. Although the need to monitor private drinking water wells is recognized (14), access to wells can be difficult and requires explicit permission from landowners. Another challenge is that scientific studies often lack critical temporal perspective (i.e. pre- and post- drilling), as drilling activities often outpace the ability for scientists to commence a well-controlled study. Thus, given that NORM is present in most groundwater, source-term attribution of NORM found in drinking water wells can be challenging. Taken together, these observations and the 57

77 paucity of well-controlled studies complicates a scientific assessment of the relationship between unconventional drilling activities and NORM mobilization into ground water. An opportunity for a small pilot study arose to investigate the potential for mobilization of NORM into groundwater due to unconventional drilling activities. Based on our experience with produced fluids from the Marcellus Shale region of the US, we focused our pilot study on levels of natural uranium ( nat U: 238 U, t1/2 = years; 235 U, t1/2 = years; 234 U, t1/2 = years), lead-210 ( 210 Pb, t1/2 = 22.2 years), and polonium-210 ( 210 Po, t1/2 = 138 days) in private drinking wells (with permission) in the north San Juan Basin of southwestern Colorado, USA (12). This area was chosen because we were able to obtain a sample of water that was collected weeks before a hydraulic fracture that occurred in January, Additionally, the San Juan Basin is a unique location to study the connection between drilling and NORM, as the region is renowned for fossil fuel resources and natural uranium ( nat U) deposits (15). In 2000 over 80% of the US coalbed methane was extracted from the San Juan Basin, mostly from the Fruitland formation (late Cretaceous) (16). Most (90%) of this gas is extracted from an area termed the Fairway, which is hydrostatically over-pressured (17). In addition to large volumes of natural gas, wells in this area produce large volumes of water with mg/l total dissolved solids (TDS) (17). Like many oil and gas rich regions in the world, the San Juan Basin is experiencing a boom in unconventional drilling, as operators seek to extract oil and natural gas from deeper shale formations (18). Many landowners are concerned that these expanded unconventional drilling operations may introduce contaminants into drinking water resources. Thus, the goal of this pilot project was to determine if levels of nat U, 210 Pb, and/or 210 Po significantly changed in the year following a hydraulic fracture in a relatively small sub-geographical area within an area of intensive unconventional drilling activity Materials and Methods General All reagents were ACS reagent grade or higher. NIST-traceable certified reference materials (CRM's, Eckert Ziegler Radioisotopes, Atlanta, GA USA) were used to prepare 232 U tracer (92403) and 209 Po tracer (92565), as previously described (19). All 58

78 half-lives and alpha-emission energies, with the exception of 209 Po, were extracted from the United States National Nuclear Data Center (NNDC Brookhaven National Laboratory, US Department of Energy). Emission energy of 209 Po was extracted from NNDC; however, we chose to use a half-live of years for 209 Po based on reports from the literature (20). All uncertainties are standard uncertainties with a coverage factor k = 1, unless stated otherwise (21). For all laboratory experiments, the analyst was blinded from the source of samples. Unless otherwise explicitly stated, all reported radioactivity concentrations were decay corrected to 2 January, 2013, 8:00 AM CST using standard differential equations (22) Sampling Description Duplicate groundwater samples from three private residences in the Fairway of the San Juan Basin in southwestern Colorado, USA; one surface water sample; and one municipal water sample were collected on 2 January, 2013 based on standard collection methods (23). For all water samples, 1 L was collected and acidified (ph 2 using concentrated HNO3), at least one week prior to analysis. An additional groundwater sample from residence A was collected by the owner on 22 January, Private drinking water wells ranged from approximately m in depth according to information obtained from Colorado Division of Water Resources ( Wells were approximately 2000 m from an unconventional well that was hydraulically fractured in January 2012 with 750,000 L of hydraulic fracturing fluid at a depth of 2400 m, according to information from FracFocus Chemical Disclosure Registry ( Additionally, within a 3 km radius of the homes, there are approximately 131 natural gas wells (12 of which were horizontally drilled) and 28 natural-gas/produced-water storage pits according to publically available information from the Colorado Oil and Gas Conservation Commission (COGCC, Municipal water (purified from surface water) was collected from a city recreation center. Surface water was collected downstream of the site of a former U smelter. Note that surface and municipal water samples were collected upstream of any drilling activity in the region. 59

79 Determination Radionuclide Activities 250 to 500 ml aliquots of acidified samples were analyzed for activities of nat U, 226 Ra, 210 Po, and 210 Pb using established methods (19, 24, 25). Briefly, 238 U, 235 U, and 234 U were determined by preconcentration with FeOH3, separation on TRU resin (Eichrom Technologies, USA) and TEVA resin (Eichrom), and prepared by CeF3 microprecipitation, as previously described (19). 250 ml glass vials were hermetically sealed and stored for 30 days prior to quantitation of 226 Ra by 222 Rn emanation using a RAD7 as recommended by the manufacturer (Durridge Company, Inc., USA). 210 Po activities were determined by preconcentration with FeOH3, separation on Eichrom SR- Resin, and autodeposition on Ag disks (24). 210 Pb was determined by holding samples for 467 days and measuring 210 Po as previously described (26). Approximately 3.5 half-lives of 210 Po had elapsed, suggesting that if modeled by secular equilibrium, the 210 Po had grown in to 90% of the supporting 210 Pb activity. Alpha spectra of U and Po isotopes were collected on vacuum-controlled alpha spectrometers (Alpha Analyst, Canberra Industries, USA) employing passivated ion-implanted silicon detectors (PIPS, Canberra) with a source to detector distance of approximately 10 mm as described by us previously (19). Contamination of detectors was prevented by use of thin-films (27). Activities were determined using standard isotope dilution techniques (28) Results and Discussion Uranium Alpha spectra indicated that ground water samples collected from private drinking water wells had varying activities of U isotopes (Fig. 2-1A, Table 2-1). The activities of 238 U in groundwater samples were mbq/l and the activities of 234 U were mbq/l. These levels of U do not exceed maximum contaminant levels (MCL; 30 μg/l or 750 mbq/l) established by the United States Environmental Protection Agency (US EPA), but 234 U/ 238 U ratios ranged from 1.7 to as large as 10, suggesting alpha-daughter recoil has greatly enriched 234 U in some samples (29). Notably, levels of U isotopes did not significantly change from pre-hydraulic fracture to post-hydraulic fracture at Home A. This observation suggests that U enrichment attributed to drilling activities has either 60

80 not occurred or that any nat U plumes have not yet entered drinking water supplies. Importantly, the MCL of nat U in drinking water is often determined by the mass of nat U. The majority (99%) of nat U is comprised of 238 U, meaning the mass of 238 U is used to calculate total U activity, under the assumption that the activity of 238 U and 234 U are equal (30). Our results suggest that the groundwater may not be in equilibrium, thus by measuring nat U by mass, the true activity of nat U may be greatly underestimated Lead and Polonium 210 Pb and 210 Po are the longest-lived radioactive decay products of 222 Rn, and are thus indicators of the accumulation of 222 Rn. The US EPA does not publish specific guidelines for evaluating 210 Pb or 210 Po concentrations in drinking waters. Consequently, little monitoring is performed for these radionuclides and little is known about their levels in drinking water sources, particularly from unregulated groundwater wells (31). When we tested for 210 Pb (average recovery 44%) and 210 Po (average recovery 30%), we found relatively low levels, each below recommended gross-beta and gross-alpha levels, respectively (Fig. 2-1B, Table 2-1). Levels of 210 Po ranged from 1.8 ± 0.7 mbq/l to 15.4 ± 1.6 mbq/l in groundwater. Note, because of sample holding time (>one year) and the number of elapsed 210 Po half-lives (>3), we were unable quantitate 210 Po levels in the pre-fracture sample from Home A. After holding samples for over one year, we remeasured 210 Po to estimate 210 Pb, based on the principles of secular equilibrium. Levels of 210 Pb ranged from 7.6 ± 0.5 to 25.0 ± 1.2 mbq/l, post-fracture. The higher levels of 210 Pb relative to 210 Po in ground water samples is likely due to differences in particle reactivity and mobility of Pb and Po in the aquifer. We observed a potential increase in levels of 210 Pb at Home A, one year after the hydraulic fracturing operation. However, large uncertainties and small sample size of this pilot study limit the scope of any conclusions based on these data. Some stakeholders are concerned that contamination from hydraulic fracturing may be introduced to drinking water aquifers through: (1) 222 Rn migration from geologic formations due to introduced fractures, (2) 226 Ra contamination arising from spills, or (3) 226 Ra and/or 222 Rn migration through cracked well-casing. Thus, although we noted a slight increase in 210 Pb, our data does not suggest that increases of NORM in groundwater have occurred outside the range of natural variations (Fig. 2-2). 61

81 Limitations Opportunities to sample private drinking water resources in the pre- and postdrilling setting are rare and this study represents a pilot investigation of important natural radionuclides of interest within this context. Apparent increases in 210 Pb observed at Home A in this study are not statistically significant and are limited by the small number of samples collected and analyzed. The levels of 226 Ra were below detection limits for our instrumentation, thus we were unable to determine its equilibrium status with 210 Pb. Further studies are needed to expand the scope and range of future work to enable statistically significant conclusions. Future studies are expected to include assessment of the levels of 222 Rn in ground water. More sensitive methods to determine the activities of 226 Ra, such as MnO2 coprecipitations traced with 133 Ba (32), can also be employed to improve detection limits for 226 Ra Conclusions As national and global demand for oil and natural gas expands, fossil-fuel-rich regions of the world will likely experience more exploratory and commercial unconventional drilling activities. New drilling techniques have been introduced to the San Juan Basin region, allowing operators to extract oil and natural gas from previously unreachable formations, such as the Morrison formation, Mancos Shale, and Gallup Sandstone (18, 33). Some of these formations are known to contain significant concentrations of NORM, such as the Morrison formation, from which 150,000,000 kg of U3O8 were extracted from between 1948 and 1986 (34, 35). Given the presence of NORM in underlying strata, there is the potential for unintended contamination of drinking water sources (aquifers) by radionuclides (e.g., U isotopes, Ra isotopes, 210 Pb, and 210 Po). These potential contamination events will likely be isolated to areas near the drilling operations, in regions where most drinking water is supplied from aquifers. Yet, many of the private wells used to extract drinking water from such aquifers are unlikely to be monitored by state and local environmental/public health agencies. Thus, there is a need to expand monitoring of these wells, particularly before drilling operations take place. Limited sample size and scope limits any conclusions based on the data presented here. However, this pilot study provides a basis upon which to build future expanded 62

82 studies to develop a more detailed understanding of the potential impact of co-extracted NORM on drinking water resources Acknowledgments We would likely to kindly acknowledge the owners of wells sampled in this study for allowing us obtain samples. Funding for these experiments was provided by the U.S. Nuclear Regulatory Commission (NRC-HQ-12-G ) 63

83 2.7. References 1. Kerr, R. A. Natural Gas From Shale Bursts Onto the Scene. Science 2010, 328, Annual Energy Outlook 2014 Early Release; U.S. Energy Information Administration, U.S. Department of Energy, Washington, D.C., Howarth, R. W.; Ingraffea, A.; Engelder, T. Natural gas: Should fracking stop? Nature 2011, 477, Howarth, R.; Santoro, R.; Ingraffea, A.. Methane and the greenhouse-gas footprint of natural gas from shale formations. Clim. Change 2011, 106, Goldstein, B. D.; Kriesky, J.; Pavliakova, B. Missing From The Table: Role of the Environmental Public Health Community in Governmental Advisory Commissions Related to Marcellus Shale Drilling. Environ. Health Perspect. 2012, 120, Gregory, K. B.; Vidic, R. D.; Dzombak, D. A. Water Management Challenges Associated with the Production of Shale Gas by Hydraulic Fracturing. Elements 2011, 7, Vidic, R. D.; Brantley, S. L.; Vandenbossche, J. M.; Yoxtheimer, D.; Abad, J. D.. Impact of Shale Gas Development on Regional Water Quality. Science 2013, 340, Brown, V. Radionuclides in Fracking Wastewater: Managing a Toxic Blend. Environ. Health Perspect. 2014, 122, A50-A Osborn, S. G.; Vengosh, A.; Warner, N. R.; Jackson, R. B. Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, Warner, N. R.; Jackson, R. B.; Darrah, T. H.; Osborn, S. G.; Down, A.; Zhao, K.; White, A.; Vengosh, A. Geochemical evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania. Proc. Natl. Acad. Sci. U. S. A. 2012, 109,

84 11. Study of the potential impacts of hydraulic fracturing on drinking water resources: progress report. US Environmental Protection Agency, Washington D.C. (USEPA Publication 601/R-12/011) Nelson, A. W.; Eitrheim, E. S.; Knight, A. W.; May, D. M.; Mehrhoff, M. A.; Shannon, R.; Litman, R.; Burnett, W. C.; Forbes, T. Z.; Schultz, M. K. Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale. Environ. Health Perspect. 2015, 123, Basic Information about the Radionuclides Rule. US Environmental Protection Agency, Washington, D.C DeSimone, L.A. Quality of water from domestic wells in principal aquifers of the United States, Overview of major findings. U.S. Geological Survey Circular, 2009, Finch, W.I.; Huffman, A.C.; Fassett, J.E; Ridgley, J.L.; Zech, R.S.; Condon, S.M.; Alief, M.H.; McLemore, V.T. Coal, uranium, and oil and gas in Mesozoic rocks of the San Juan Basin: anatomy of a giant energy-rich basin: Sandia Mountains to Mesita, New Mexico June 30 July 7, Am. Geophys. Union 1989, Ayers Jr, W. B. Coalbed gas systems, resources, and production and a review of contrasting cases from the San Juan and Powder River basins. AAPG Bulletin, 2002, 86 (11), Study to evaluate the impacts to USDWs by hydraulic fracturing of coalbed methane reservoirs. US Environmental Protection Agency, Washington, D.C. (USEPA Publication 816-R ) Sakelaris, N. Could the Mancos Shale be the next big thing? Encana says yes. Dallas Bus. J Knight, A.W.; Eitrheim, E.S.; Nelson, A.W.; Nelson, S.; Schultz, M.K. A simple-rapid method to separate uranium, thorium, and protactinium for U-series agedating of materials. J. Environ. Radioact. 2014, 134,

85 20. Collé, R.; Laureano-Perez, L.; Outola, I. A note on the half-life of 209 Po. Appl. Radiat. Isot. 2007, 65, Currie, L.A. Limits for qualitative detection and quantitative determination. Application to radiochemistry. Anal. Chem. 1968, 40, Bateman, H. The solution of a system of differential equations occurring in the theory of radioactive transformations, Proc. Cambridge Philos. Soc. 1910, 15, Collection of water samples (ver. 2.0): U.S. Geological Survey techniques of water-resources investigations. U.S. Geological Survey, Department of Interior, Washington, D.C. 2006, 9 (A4). 24. Eichrom Technologies LLC. Analytical Procedures: Lead-210 and Polonium- 210 in Water. [Online], (accessed 16 June 2015). 25. Nelson, A. W.; May, D.; Knight, A. W.; Eitrheim, E. S.; Mehrhoff, M.; Shannon, R.; Litman, R.; Schultz, M. K. Matrix Complications in the Determination of Radium Levels in Hydraulic Fracturing Flowback Water from Marcellus Shale. Environ. Sci. Technol. Lett. 2014, 1, Vesterbacka, P.; Ikäheimonen, T. K. Optimization of 210 Pb determination via spontaneous deposition of 210 Po on a silver disk. Anal. Chim. Acta, 2005, 545 (2), Inn, K.G.W.; Hall, E.; Woodward, J.T.; Stewart, B.; Pöllänen, R.; Selvig, L.; Turner, S.; Outola, I.; Nour, S.; Kurosaki, H.; LaRosa, J.; Schultz, M.K.; Lin, Z.; Yu, Z.; McMahon, C. Use of thin collodion films to prevent recoil-ion contamination of alphaspectrometry detectors. J. Radioanal. Nucl. Chem. 2008, 276,

86 28. Makarova, T.; Preobrazhenskaya, L.D.; Lovtsyus, A.V.; Fridkin, A.M.; Stepanov, A.V.; Lipovskii, A.A.; Belyaev, B.N. Application of isotope dilution method for mass-and alpha-spectrometric determination of burn-up and uranium, plutonium and transplutonium element content in VVER-440 spent fuel. J. Radioanal. Nucl. Chem. 1983, 80 (1), Osmond, J.; Cowart, J.; Ivanovich, M. Uranium isotopic disequilibrium in ground water as an indicator of anomalies. Int. J. Appl. Radiat. Isot. 1983, 34, Analytical Methods Approved for Drinking Water Compliance Monitoring of Radionuclides. US Environmental Protection Agency, Washington, D.C. (USEPA Publication 815-B ) Ruberu, S. R.; Liu, Y.G.; Perera, S.K. Occurrence and distribution of 210 Pb and 210 Po in selected California groundwater wells. Health Phys. 2007, 92 (5), Maxwell III, S. Rapid method for 226 Ra and 228 Ra analysis in water samples. J. Radioanal. Nucl. Chem., 2006, 270 (3), Zah, E.. BLM seeks to amend land-use plan for drilling. Albuquerque J Turner-Peterson, C.E.; Fishman, N.S. Geologic synthesis and genetic models for uranium mineralization in the Morrison Formation, Grants uranium region, New Mexico. AAPG 1986, 22, McLemore, V.T., Chenoweth, W.L. Uranium resources in the San Juan Basin, New Mexico. N. M. Geol. Soc. Guideb., 2003, 54, Fassett, J.E. Cretaceous and tertiary rocks of the eastern San Juan Basin, New Mexico and Colorado. N. M. Geol. Soc. Guideb., 1974, 25,

87 A 100 Activity (mbq/l) U 235 U 234 U B 0 40 Home A pre Home A post Home B Home C Municipal Surface 210 Pb Activity (mbq/l) * 210 Po 10 0 Home A pre Home A post Home B Home C Municipal Surface Figure 2-1 Activities of NORM in water collected from homes, a river and a municipal building in an area with unconventional drilling operations. (A) natural-uranium activities ( 238 U (blue), 235 U (grey), 234 U (green)) in Jan (B) lead-210 ( 210 Pb, (brown)) and polonium-210 ( 210 Po, (red)) activities on Jan 2013 and one home on Jan Uncertainties are based on duplicate measurements and counting statistics. (*) 210 Po reported, but due to sample holding times does not represent unsupported 210 Po. 68

88 Figure 2-2 Schematic of possible NORM contamination pathways of groundwater near hydraulic fracturing operations. Solid lines indicate a radioactive decay or series of radioactive decays. Dashed lines indicate transportation in the environment. Geologic data adapted from a published source (36). Note, geologic formations are not to scale for illustrative purposes. 69

89 Table 2-1 Activities of Radionuclides from Selected Sites in Southern Colorado. 238 U 235 U 234 U 234 U/ 238 U 226 R a 210 Pb b 210 Po Municipal 5.0 ± ± 0.1 Stream 36 ± ± 0.3 Home B (1) 47 ± ± 0.3 Home B (2) 46 ± ± 0.5 Home C (1) 7.3 ± ± 0.2 Home C (2) 8.7 ± ± 0.2 Home A (1) 3.7 ± ± 0.2 Home A (2) 3.3 ± ± 0.4 Home A (3) a 2.8 ± ± ± <LODc 1.0 ± ± ± <LOD 3.0 ± ± ± <LOD 7.6 ± ± ± <LOD 10.0 ± 5.2 ± ± 2 10 <LOD 24.3 ± 10.0 ± ± <LOD 20.5 ± 5.3 ± ± <LOD 19.9 ± 13.2 ± ± <LOD 25.0 ± 15.4 ± ± 1 10 <LOD 14.3 ± 15.2 ± All activities reported as mbq/l. All uncertainties correspond to k = 1. All samples collected 2 January 2013, unless otherwise stated. a Sample collected 22 January b Inferred from 210 Po (assumed in secular equilibrium on 17 April 2014). c LOD approximately 100 mbq/l. 70

90 CHAPTER 3: MATRIX COMPLICATIONS IN THE DETERMINATION OF RADIUM LEVELS IN HYDRAULIC FRACTURING FLOWBACK WATER FROM MARCELLUS SHALE This chapter was published on 10 February, This chapter is reprinted with permission. Please refer to: Nelson, A. W.; May, D.; Knight, A. W.; Eitrheim, E. S.; Mehrhoff, M.; Shannon, R.; Litman, R.; Schultz, M. K. Matrix Complications in the Determination of Radium Levels in Hydraulic Fracturing Flowback Water from Marcellus Shale. Environ. Sci. Technol. Lett. 2014, 1, Abstract The rapid proliferation of horizontal drilling and hydraulic fracturing for natural gas mining has raised concerns about the potential for adverse environmental impacts. One specific concern is the radioactivity content of associated flowback wastewater (FBW), which is enhanced with respect to naturally occurring radium (Ra) isotopes. Thus, development and validation of effective methods for analysis of Ra in FBW are critical to appropriate regulatory and safety decision making. Recent government documents have suggested the use of EPA method for isotopic Ra determinations. This method has been used effectively to determine Ra levels in drinking water for decades. However, analysis of FBW by this method is questionable because of the remarkably high ionic strength and dissolved solid content observed, particularly in FBW from the Marcellus Shale region. These observations led us to investigate the utility of several common Ra analysis methods using a representative Marcellus Shale FBW sample. Methods examined included wet chemical approaches, such as EPA method 903.0, manganese dioxide (MnO2) preconcentration, and 3M Empore RAD radium disks, and direct measurement techniques such as radon (Rn) emanation and high-purity germanium (HPGe) gamma spectroscopy. Nondestructive HPGe and emanation techniques were effective in determining Ra levels, while wet chemical techniques recovered as little as 1% of 226 Ra in the FBW sample studied. Our results question the reliability of wet chemical techniques for the determination of Ra content in Marcellus Shale FBW (because of the remarkably high ionic strength) and suggest that 71

91 nondestructive approaches are most appropriate for these analyses. For FBW samples with a very high Ra content, large dilutions may allow the use of wet chemical techniques, but detection limit objectives must be considered Introduction New horizontal drilling technologies combined with hydraulic fracturing have the potential to unlock significant reserves of previously unrecoverable shale-bound natural gas around the world (1-3). However, the rapid proliferation of these drilling techniques has sparked debate over the potential for undesirable environmental impacts. One specific concern is the radioactivity content of produced fluids and flowback wastewater (collectively termed FBW), which is typically enriched in naturally occurring radium (Ra) isotopes (4, 5). For example, concentrations of 226 Ra and 228 Ra in FBW from the Marcellus Shale formation in the United States (underlying New York, Pennsylvania, West Virginia, and Ohio) have been reported in peer-reviewed studies to be as high as 626 and 96 Bq/L, respectively (4). Although these levels are not sufficient to cause acute radiotoxicity, the large volumes and high ionic strength of FBW can overwhelm wastewater treatment facilities,(6) giving rise to radioactive contamination downstream of wastewater treatment plant discharges. For example, a recent peer-reviewed report documents 226 Ra contamination of approximately 200 times background in sediments downstream of a wastewater treatment plant in Pennsylvania (7). Given the magnitude of Marcellus FBW waste (>5 billion L in 2014 alone), (8) operators and government agencies are considering regulations to monitor wastewaters to ensure appropriate radiation and environmental protection strategies are in place. One challenge to effective radiation and environmental protection for these activities is obtaining an accurate assessment of the radioactivity concentration of Ra isotopes in samples of FBW. Methods for quantitating isotopic Ra radioactivity in FBW have not been validated, and few peer-reviewed data sets on this topic are available. Several studies have referred to data originating from the Pennsylvania Department of Environmental Protection, which for some samples quantitated 226 Ra and 228 Ra by routine drinking water methods, specifically EPA method and EPA method (4, 5, 9). In another example, the New York State Department of Environmental Conservation 72

92 proposed in 2009 (revised in 2011) that all FBW must be measured for radioactivity (before discharge) using EPA method (alpha-emitting Ra isotopes in drinking water) and EPA method ( 228 Ra in drinking water) to quantify 226 Ra and 228 Ra (page 6-61) (10). Although wet chemical methods are robust for drinking water, because of the remarkably high ionic strength of FBW (particularly from the Marcellus Shale), the reliability of methods such as EPA method and EPA method is questionable for analysis of FBW. Thus, the goal of this study was to investigate the utility of several methods for analysis of Ra isotopes in a representative sample of Marcellus Shale FBW. We explored BaSO4 coprecipitation (EPA method 903.0), manganese dioxide (MnO2) preconcentration, a rapid 3M Empore RAD radium disk approach, analysis of 226 Ra via radon ( 222 Rn) gas emanation using a portable RAD7 electronic Rn spectrometer, and high-purity germanium (HPGe) high-resolution gamma spectroscopy. Our results suggest strongly that nondestructive spectroscopic techniques are most appropriate for analysis of high-ionic strength FBW Materials and Methods General All reagents were ACS grade or higher. The State Hygienic Laboratory at the University of Iowa complies with standards of operation and quality assurance required for accreditation by the U.S. National Environmental Laboratory Accreditation Program (NELAP). All radioactivity values are decay-corrected to 2:18 p.m. (CST) on May 15, Unless otherwise stated, all uncertainties are standard uncertainties, corresponding to a one-uncertainty interval based on the standard deviation of multiple measurements or an estimate thereof, according to principles adhered to by international standards bodies (11) Flowback Wastewater Sample The University of Iowa State Hygienic Laboratory (SHL) received a 200 L drum of Marcellus Shale FBW from northeastern Pennsylvania. The sample was extracted from a 2100 m deep, horizontally drilled well, which was hydraulically fractured with approximately m 3 of hydraulic fracturing fluid in early The sample was 73

93 received May 7, Prior to radium quantitation, analysts at SHL determined the chemical composition by standard environmental techniques (Table S1-1 of Appendix 1) Surrogate Matrix A surrogate blank matrix was prepared for quality assurance/quality control (QA/QC) analysis using reagent grade NaCl, KCl, MgCl2 6H2O, CaCl2, SrCl2 6H2O, BaCl2 2H2O, and FeCl3 in deionized water (dh2o). The surrogate was prepared to match as closely as possible the FBW sample matrix based on mass spectrometry analysis (Table S1-1 of Appendix 1) Methods of Analysis Tested BaSO4 Coprecipitation We attempted to use the EPA method isotopic Ra in drinking water method of analysis. However, the addition of 20 ml of 18 M H2SO4, prescribed by this method, formed excessive volumes of precipitate, which rendered the approach intractable. In a further attempt to utilize the technique, we developed a modified EPA method protocol. Briefly, three 100 ml samples of FBW, three 100 ml surrogate samples spiked with 3.7 Bq of 226 Ra, and one 100 ml surrogate blank were diluted to 1 L with dh2o. EPA method was then followed with two modifications: (1) only 0.5 ml of 1 M H2SO4 was added at the precipitation step (rather than the prescribed 20 ml of 18 M H2SO4), and (2) the Ba carrier was omitted. Counting sources were prepared according to the EPA method protocol and were counted on a gas flow proportional counter (Berthod LB 770) for 50 min as prescribed by the method M Empore RAD Radium Disks ( RAD disks ) RAD disks (3M, Eagan, MN) are wide-area (47 mm diameter) filter-based materials impregnated with a chromatographic extractant that is designed to selectively remove Ra from aqueous samples (12). In our attempt to employ this technology for FBW analysis, three 50 ml samples of FBW were diluted to 500 ml with dh2o and filtered through RAD disks, according to the manufacturer s recommendations. Disks were counted for 17 h on a Canberra HPGe detection system, calibrated to a 47 mm diameter wide-area filter geometry [Eckert and Ziegler (E&Z) 93471]. Filtrates were collected in 0.5 L Marinelli beakers and counted for 17 h using a 0.5 L liquid geometry, 74

94 calibrated for energy and efficiency with an identical geometry NIST traceable standard (E&Z 93472). The radioactivity concentrations of 226 Ra in the filtrates and filters were determined by the 186 kev peak as described previously (13, 14) Rn Emanation Measurement by RAD7 Several methods are used frequently to determine 226 Ra levels in liquid matrices based on emanation and measurement of 222 Rn, including mineral oil extraction and liquid scintillation counting and Lucas cell emanation-based gross-counting techniques. We evaluated the emanation approach using RAD7 (DURRIDGE Co., Inc., Billerica, MA), an electronic radon detector that quantifies isotopic radon activity based on measurement of short-lived alpha-emitting Rn daughters by high-resolution alpha spectrometry (15). All materials for the RAD7 experiments were purchased from DURRIDGE and used according to the manufacturer s instructions or in consultation with the manufacturer. Briefly, glass vials (250 ml) were filled with FBW and hermetically sealed for at least 30 days to reach secular equilibrium between 226 Ra and 222 Rn. Samples were analyzed using the RAD H2O accessory package, with the following minor manufacturer-recommended modification: an empty desiccant tube was inserted into the apparatus to control foaming of FBW and the relative humidity in the detector. Activities were calculated by the preprogrammed WAT250 protocol, adjusted for relative humidity with DURRIDGE Capture version 5.2.2, and decay corrected. QA/QC checks with samples of known 226 Ra activity (4, 40, and 100 Bq/L), analyzed as described above, were in agreement with the manufacturer s calibration of the detector MnO2 Preconcentration The method of preconcentration of Ra on MnO2 has been used often for effective Ra isotopic analysis of water samples (16-18). For our evaluation, 30 mg of KMnO4 was added to 250 ml of acidified FBW and the ph was adjusted to 7 8 with 6 M ammonium hydroxide (NH4OH) to form MnO2. Precipitates were filtered on 0.45 μm cellulose nitrate filters (Whatman). The filtrate was transferred to 250 ml glass vials, diluted with dh2o, and sealed for at least 30 days. Precipitates and filters were digested in concentrated HNO3, transferred to 250 ml glass vials, neutralized with 6 M NH4OH, and sealed for at least 30 days. Activities of 222 Rn were then determined by RAD7 by 75

95 following the manufacturer-recommended protocol (15). In this way, the efficiency of the MnO2 in sequestering Ra could be assessed by the difference between the filtrate concentration and the filtered MnO2 levels Gamma Spectroscopy HPGe gamma spectrometry analysis of FBW was conducted according to routine procedures using NIST traceable standards. Briefly, HPGe gamma spectrometers were calibrated to (1) a 3 L Marinelli beaker liquid geometry (E&Z 93474), (2) a 47 mm widearea filter geometry (E&Z CRM 93471), or (3) a 0.5 L Marinelli beaker liquid geometry (E&Z 93472), as appropriate. QA/QC included linearity and efficiency checks performed three times per week and weekly background counts. Once the bulk sample of FBW had been received, 3 L was transferred to a 3 L Marinelli beaker. Because of the settling of ultrafine particulate matter, 51 g of Bacto Agar (BD ) was added. The sample was heated to a low boil and then slowly cooled to form a homogeneous suspension. Gamma emissions were measured for 17 h on a 30% efficient ORTEC (Ametek, Oak Ridge, TN) HPGe, calibrated to a 3 L liquid Marinelli geometry (E&Z 93474). After 62 days, the sample was recounted on an 18% Canberra HPGe gamma detector (calibrated to E&Z 93474) to confirm ingrowth of short-lived daughters, 214 Pb, 212 Pb, and 214 Bi. Spectral analysis was performed using ORTEC GammaVision version 6.08 with a library that included NORM expected in FBW. Emission energies, half-lives, and their uncertainties were extracted from the National Nuclear Data Center ( (19) Results and Discussion Chemical Matrix Analysis of the elemental composition revealed the FBW used for this study has high concentrations of monovalent and divalent ions, solids, and transition metals (Table S1-1 of the Appendix 1). Briefly, concentrations of monovalent and divalent ions were as follows: mg/l Cl, mg/l Sr, mg/l Na, mg/l Ca, 9000 mg/l Ba, 850 mg/l Mg, and 160 mg/l K. The concentration of the total dissolved solids was mg/l and that of the total suspended solids 780 mg/l. The concentrations of Pb, 76

96 Fe, and Mn were 1.0, 43, and 3.4 mg/l, respectively. The high concentrations of solids, Sr, and Ba are characteristic of Marcellus Shale FBW reported previously (5, 9, 20) Barium Sulfate Coprecipitation The first method we investigated is commonly used for Ra concentration determinations in drinking water, i.e., EPA method This method involves the addition of BaCl2 and H2SO4 to precipitate Ra as Ba(Ra)SO4. We found that following the procedure as written results in copious, unmanageable quantities of precipitate. Because of excessive precipitate formation, we were unable to use EPA method to quantify Ra activities in samples as small as 10 ml. To determine whether a modified form of EPA method would be useful, we reduced the quantity of H2SO4 by a factor of 720 and diluted the salt concentration by a factor of 10. This reduced the final precipitate to acceptable mass ranges but resulted in poor recovery of Ra. Activities of 226 Ra surrogate spikes were calculated to be <1% of spiked activity. Similarly, activities of FBW were calculated to be <1% of the 226 Ra activity determined by HPGe. We interpret this finding as illustrating that the similar chemistry of Ra and Ba prevents the use of Ba(Ra)SO4 precipitation in samples with large Ba:Ra mass ratios (nearly 1:10 9 in this sample), as are commonly found in FBW. Thus, our data suggest that Ba(Ra)SO4 coprecipitations are not appropriate for analysis of FBW in general and (in particular) for the analysis of Marcellus Shale FBW. These laboratory findings may also explain observed difficulties experienced by wastewater treatment facilities (using similar coprecipitation approaches) in removing Ra from FBW, (7) potentially leading to improved wastewater treatment strategies M Empore Radium RAD Disks RAD disks have been used successfully to concentrate Ra from aqueous environmental samples (21, 22). The use of the RAD disk technology is appealing, because the approach is rapid, with fewer wet chemical steps than BaSO4 coprecipitations (21). The manufacturer reports the disks recover >95% of Ra in samples with high concentrations of divalent cations, although a published peer-reviewed upper limit of metal concentration has not been established, to the best of our knowledge (12). When we tested 50 ml of FBW, diluted 10-fold in dh2o, the recovery of 226 Ra was 13 ± 1% (n = 77

97 3) of values obtained by direct measurement using HPGe. Although recovery was low, others have suggested radioactive tracers, such as 133 Ba or 225 Ra, could be used for isotope dilution-based approaches (22, 23). Nonetheless, the efficiency of the RAD disk appears to be questionable for high-ionic strength FBW, and a more thorough study is needed to establish an upper limit of ionic strength within which the technology can be reliably employed for analysis of FBW MnO2 Preconcentration Manganese dioxide is used often to preconcentrate Ra for radiochemical analysis (16-18). However, we hypothesized the divalent-rich matrix of FBW would hinder the efficiency of the approach. To test this assertion, we performed MnO2 preconcentration of FBW to determine if 226 Ra would sorb to MnO2 or remain in solution. Results indicated that MnO2 scavenged <1% of 226 Ra from the FBW (i.e., the filtrate contained >99% of the 226 Ra). Although preconcentration with MnO2 is useful for certain complex matrices, high-ionic strength brine, such as that from the Dead Sea, has been reported to reduce Ra recovery on MnO2-impregnated acrylic fibers (24). Similarly, our results indicate that the high concentrations of divalent cations in FBW interfere with the use of MnO2-based preconcentration for the analysis of FBW Rn Emanation Measurement by RAD7 RAD7 is a sturdy, portable, electronic radon detector that can be used to measure 222 Rn and 220 Rn (decay products of 226 Ra and 224 Ra, respectively) in environmental water samples in field and laboratory environments (25-27). The system can be used to measure unsupported 222 Rn and 220 Rn levels in water, by immediate measurement, as well as 226 Ra and 224 Ra by hermetically sealing water samples and allowing sufficient time for Rn radioactivity products to reach radioactive equilibrium. When the RAD H2O closed-loop system is used, the RAD7 can measure 222 Rn activities in water from <0.37 to Bq/L (15). Measurement of 226 Ra in FBW via 222 Rn emanation is advantageous relative to wet chemical analysis techniques because Rn gas can be stripped from complex chemical matrices, allowing for sample volumes larger than and detection limits lower than those of precipitation methods. On the other hand, for analysis of the Marcellus Shale FBW sample described here, controlling foam produced during the Rn gas-stripping process 78

98 using RAD7 was a challenge. To alleviate the problem, we inserted an empty desiccant tube between the sample vial and the filled desiccant tube. Another (related) challenge was controlling the humidity in the detector chamber, which can reduce the counting efficiency of the RAD7 device. When adjusted for humidity using the DURRIDGE Capture software and for volume introduced by the empty desiccant tube, the radioactivity level of the 226 Ra level in FBW observed in this study was 610 ± 10 Bq/L (n = 3). This estimation of 226 Ra may differ from HPGe values for several reasons, including the effects of brine on the solubility of Rn (28). Additionally, modifications to the RAD7 may be necessary to reduce possible interference from dissolved gases (29). A more rigorous examination of these parameters is ongoing in our laboratory. If analysis of large numbers of samples is required rapidly, in a high-throughput laboratory environment, mineral oil-based 222 Rn extraction/emanation and liquid scintillation counting and Lucas cell-based emanation techniques can be employed to improve throughput. A potential drawback of 226 Ra measurements by this method is the holding time for radon ingrowth. The holding time may be as short as 4 days if the sample is purged prior to being hermetically sealed; however, because sample foaming prevented complete purging, we chose to hold for 30 days to establish secular equilibrium. Thus, for samples with sufficient 226 Ra radioactivity content, direct measurement by HPGe gamma spectroscopy (as described below) may offer a simpler solution to achieving statistical significance in radioactivity quantitation HPGe Gamma Spectroscopy HPGe gamma spectroscopy is well-established for the determination of the levels of 228 Ra, 226 Ra, and 224 Ra in environmental samples, with achievable detection limits depending primarily on sample size, detector efficiency, and available counting time (30-32). Within these constraints, given that the Ra isotopic concentration of Marcellus Shale FBW is relatively high, the clear advantage of HPGe gamma spectroscopy for the analyses here is the simplicity of sample handling (i.e., no wet chemistry required; apart from the addition of agar and moderate heating, no alterations were made to the sample). Thus, high-ionic strength FBW samples can be measured directly, and samples can be stored for future analysis (if required). Radium activities observed in the representative FBW sample used for this assessment are well in excess of typical environmental levels 79

99 in natural surface waters reported in this region of Pennsylvania [ 226 Ra, 670 ± 3 Bq/L; 228 Ra, 76 ± 1 Bq/L (Table 3-1)] (7). 228 Ra activities were determined by integration of 228 Ac radioactive product peaks (911 and 338 kev), with an achievable minimal detectable activity (MDA) of 0.6 Bq/L under the counting conditions employed. The 226 Ra value was determined on the basis of a direct measurement of the 186 kev 226 Ra peak, with an achievable MDA of 3 Bq/L. Although interference from 235 U gamma ray emission in the 186 kev region is possible, (33) preliminary analysis of natural U isotopes 238 U, 235 U, and 234 U by alpha spectrometry reveals activities of <0.01 Bq/L of FBW. Thus, the contribution of 235 U to the 186 kev region is negligible for these analyses. Very little natural U is extracted during the hydraulic fracturing process because of the insolubility of U under the reducing conditions at depth in the shale deposit. Further studies are required to develop a detailed understanding of the behavior of U in unconventional, drilling-derived solid waste and in the FBW use cycle (a topic of current research in our laboratories). Lower radioactivity concentrations of 228 Ra (and decay products 224 Ra, 212 Pb, and 208 Tl) relative to those of 226 Ra (and decay products 214 Pb and 214 Bi) can be explained by a lower concentration of natural Th ( 232 Th relative to natural 238 U) at depth in the shale deposit. Importantly, regardless of the decay product equilibrium and/or disequilibrium associated with FBW, direct measurement of 226 Ra requires no holding time and can be measured directly by HPGe via the 186 kev gamma ray emission of 226 Ra. When possible, measurements conducted using the 186 kev peak can be confirmed by measuring 226 Ra decay product ingrowth after the proper holding time. The radioactive equilibrium of 228 Ac (t1/2 = 6 h) with 228 Ra is reached in 36 h for these analyses. While ionic strength differences between control standards and high-ionic strength samples under analysis can contribute to inaccuracies in Ra isotopic measurements due to density differences, our analysis of surrogate FBW indicates no significant contribution (34). Differences in the 226 Ra radioactivity level determined by the RAD7 emanation method may be the result of inaccuracies in humidity corrections applied, and an improved apparatus can easily be envisioned for efficient field studies by this emanation technique (a topic of ongoing research in our laboratories). Nonetheless, our results strongly suggest that wet chemical techniques (e.g., EPA method 903.0) are unlikely to be reliable for the analysis of high-ionic strength FBW, and direct 80

100 measurement by emanation techniques and HPGe spectroscopy is recommended for accurate assessments. For FBW samples with a very high Ra content, large dilutions may be applied (to dilute the ionic strength) to allow the use of wet chemical techniques, but detection limit data quality objectives must be considered Acknowledgment We kindly acknowledge the staff and personnel at the University of Iowa State Hygienic Laboratory for facilitating a productive practical experience for A.W.N. for this study. Funding for these studies was provided by the U.S. Nuclear Regulatory Commission (NRC-HQ-12-G ) and Environmental Management Solutions (Contract EMS FP ). 81

101 3.6. References 1. Moniz, E. J.; Jacoby, H. D.; Meggs, A. J. M.; Armtrong, R. C.; Cohn, D. R.; Connors, S. R.; Deutch, J. M.; Ejaz, Q. J.; Hezir, J. S.; Kaufman, G. M. The Future of Natural Gas; MIT Press: Cambridge, MA, Holditch, S.; Perry, K.; Lee, J. Unconventional Gas Reservoirs: Tight Gas, Coal Seams, and Shales. Working Document of the National Petroleum Council on Global Oil and Gas Study; National Petroleum Council: Washington, DC, Kerr, R. A. Natural Gas from Shale Bursts onto the Scene. Science 2010, 328 ( 5986) Rowan, E.; Engle, M.; Kirby, C.; Kraemer, T. Radium Content of Oil- and Gas- Field Produced Waters in the Northern Appalachian Basin (USA): Summary and Discussion of Data Sci. Invest. Rep. (U.S. Geol. Surv.) 2011, 5135, Haluszczak, L. O.; Rose, A. W.; Kump, L. R. Geochemical evaluation of flowback brine from Marcellus gas wells in Pennsylvania, USA Appl. Geochem. 2013, 28, Gregory, K. B.; Vidic, R. D.; Dzombak, D. A. Water Management Challenges Associated with the Production of Shale Gas by Hydraulic Fracturing. Elements 2011, 7 (3) Warner, N. R.; Christie, C. A.; Jackson, R. B.; Vengosh, A. Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania. Environ. Sci. Technol. 2013, 47 ( 20) Lutz, B. D.; Lewis, A. N.; Doyle, M. W. Generation, transport, and disposal of wastewater associated with Marcellus Shale gas development. Water Resour. Res. 2013, 49 (2) Barbot, E.; Vidic, N. S.; Gregory, K. B.; Vidic, R. D. Spatial and Temporal Correlation of Water Quality Parameters of Produced Waters from Devonian-Age Shale following Hydraulic Fracturing. Environ. Sci. Technol. 2013, 47 (6)

102 10. Supplemental Generic Environmental Impact Statement On The Oil, Gas and Solution Mining Regulatory Program; New York State Department of Environmental Conservation: Albany, NY, Currie, L. A. Limits for qualitative detection and quantitative determination. Anal. Chem. 1968, 40 (3) Empore TM Radium RAD Disks Method Summary: Test Method RA-195 ( (accessed January 17, 2014). 13. Seely, D. C.; Osterheim, J. A. Radiochemical analyses using Empore TM Disk Technology J. Radioanal. Nucl. Chem. 1998, 236 (1 2) Rihs, S.; Condomines, M. An improved method for Ra isotope ( 226 Ra, 228 Ra, 224 Ra) measurements by gamma spectrometry in natural waters: Application to CO2-rich thermal waters from the French Massif Central. Chem. Geol. 2002, 182 (2 4) RAD7 ( (accessed January 10, 2014). 16. Moore, W. S. Sampling 228 Ra in the deep ocean. Deep-Sea Res. Oceanogr. Abstr. 1976, 23 (7) Burnett, J. L.; Croudace, I. W.; Warwick, P. E. Pre-concentration of shortlived radionuclides using manganese dioxide precipitation from surface waters. J. Radioanal. Nucl. Chem. 2012, 292 (1) Nour, S.; El-Sharkawy, A.; Burnett, W. C.; Horwitz, E. P. Radium-228 determination of natural waters via concentration on manganese dioxide and separation using Diphonix ion exchange resin. Appl. Radiat. Isot. 2004, 61 (6) National Nuclear Data Center, NuDat 2 database. ( (accessed May 10, 2013). 20. Chapman, E. C.; Capo, R. C.; Stewart, B. W.; Kirby, C. S.; Hammack, R. W.; Schroeder, K. T.; Edenborn, H. M. Geochemical and Strontium Isotope Characterization of Produced Waters from Marcellus Shale Natural Gas Extraction. Environ. Sci. Technol. 2012, 46 (6)

103 21. Ďurecová, A.; Ďurec, F.; Auxtová, L.; Adámek, P.; Lendacká, M. Determination of 226 Ra and 228 Ra in mineral and drinking waters using 3M s EMPORE radium RAD disks. Czech. J. Phys. 1999, 49 (1) Purkl, S.; Eisenhauer, A. A rapid method for α-spectrometric analysis of radium isotopes in natural waters using ion-selective membrane technology. Appl. Radiat. Isot. 2003, 59 (4) Ďurecová, A. Contribution to the simultaneous determination of 228 Ra and 226 Ra by using 3M s EMPORE TM radium rad disks. J. Radioanal. Nucl. Chem. 1997, 223 (1 2) Kiro, Y.; Yechieli, Y.; Voss, C. I.; Starinsky, A.; Weinstein, Y. Modeling radium distribution in coastal aquifers during sea level changes: The Dead Sea case. Geochim. Cosmochim. Acta 2012, 88, Dimova, N.; Burnett, W. C.; Lane-Smith, D. Improved Automated Analysis of Radon ( 222 Rn) and Thoron ( 220 Rn) in Natural Waters. Environ. Sci. Technol. 2009, 43 (22) Burnett, W. C.; Dulaiova, H.Estimating the dynamics of groundwater input into the coastal zone via continuous radon-222 measurements. J. Environ. Radioact. 2003, 69 (1 2) Kim, G.; Burnett, W. C.; Dulaiova, H.; Swarzenski, P. W.; Moore, W. S. Measurement of 224 Ra and 226 Ra Activities in Natural Waters Using a Radon-in-Air Monitor. Environ. Sci. Technol. 2001, 35 (23) Peterson, R. N.; Burnett, W. C.; Dimova, N.; Santos, I. R. Comparison of measurement methods for radium-226 on manganese-fiber. Limnol. Oceanogr.: Methods 2009, 7, Tuccimei, P.; Soligo, M. Correcting for CO2 interference in soil radon flux measurements. Radiat. Meas. 2008, 43 (1) Moore, W. S. Radium isotope measurements using germanium detectors. Nucl. Instrum. Methods Phys. Res. 1984, 223 (2 3)

104 31. Murray, A.; Marten, R.; Johnston, A.; Martin, P. Analysis for naturally occuring radionuclides at environmental concentrations by gamma spectrometry. J. Radioanal. Nucl. Chem. 1987, 115 (2) van Beek, P.; Souhaut, M.; Reyss, J. L. Measuring the radium quartet ( 228 Ra, 226 Ra, 224 Ra, 223 Ra) in seawater samples using gamma spectrometry. J. Environ. Radioact. 2010, 101 (7) Dowdall, M.; Selnaes, Ø. G.; Gwynn, J. P.; Davids, C.Simultaneous determination of 226 Ra and 238 U in soil and environmental materials by gammaspectrometry in the absence of radium progeny equilibrium. J. Radioanal. Nucl. Chem. 2004, 261 (3) Landsberger, S.; Brabec, C.; Canion, B.; Hashem, J.; Lu, C.; Millsap, D.; George, G. Determination of 226 Ra, 228 Ra and 210 Pb in NORM products from oil and gas exploration: Problems in activity underestimation due to the presence of metals and selfabsorption of photons. J. Environ. Radioact. 2013, 125,

105 Figure 3-1 Graphic Abstract 86

106 Table 3-1 Comparison of 226 Ra Quantitation Methods. Method BaSO4 coprecipitation Sample Description Surrogate spike (3.7 Bq of 226 Ra) FBW a and 0.5 ml of 1 M Volume (L) 226 Ra recovery (%) 226 Ra (Bq/L) 0.1 <1 b 0.15 ± d 0.1 <1 b,c 1.9 ± 0.4 d Empore RAD disk MnO2 concentration H2SO4 FBW diluted 10-fold, RAD disk FBW diluted 10-fold, supernatant FBW and 10 mg of Mn, precipitate FBW and 10 mg of Mn, supernatant ± 1 96 ± 8 d ± ± 1 d 0.25 <1 0.9 ± 0.3 d 0.25 > ± 20 d RAD7 FBW c 610 ± 10 d HPGe FBW and Bacto Agar ± 26 e a FBW, flowback water. b Assuming a 100% efficiency of Ba recovery. c Relative to the HPGe kev peak. d Uncertainties are reported as the standard deviation of three counts. e Counting uncertainty. 87

107 CHAPTER 4: UNDERSTANDING THE RADIOACTIVE INGROWTH AND DECAY OF NATURALLY OCCURRING RADIOACTIVE MATERIALS IN THE ENVIRONMENT: AN ANALYSIS OF PRODUCED FLUIDS FROM THE MARCELLUS SHALE This chapter was accepted for publication 11 March, 2015, published online on 2 April, 2015, and available in print on 1 July, This chapter is reprinted with permission. Note, that this chapter was published by the United States government and is therefore without copyright. Please refer to: Nelson, A. W.; Eitrheim, E. S.; Knight, A. W.; May, D. M.; Mehrhoff, M. A.; Shannon, R.; Litman, R.; Burnett, W. C.; Forbes, T. Z.; Schultz, M. K. Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale. Environ. Health Perspect. 2015, 123, Abstract Background The economic value of unconventional natural gas resources has stimulated rapid globalization of horizontal drilling and hydraulic fracturing. However, natural radioactivity found in the large volumes of produced fluids generated by these technologies is emerging as an international environmental health concern. Current assessments of the radioactivity concentration in liquid wastes focus on a single element radium. However, the use of radium alone to predict radioactivity concentrations can greatly underestimate total levels Objective We investigated the contribution to radioactivity concentrations from naturally occurring radioactive materials (NORM), including uranium, thorium, actinium, radium, lead, bismuth, and polonium isotopes, to the total radioactivity of hydraulic fracturing wastes Methods For this study we used established methods and developed new methods designed to quantitate NORM of public health concern that may be enriched in complex brines 88

108 from hydraulic fracturing wastes. Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM Results We observed that radium decay products were initially absent from produced fluids due to differences in solubility. However, in systems closed to the release of gaseous radon, our model predicted that decay products will begin to ingrow immediately and (under these closed-system conditions) can contribute to an increase in the total radioactivity for more than 100 years Conclusions Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment. These predictions must include an understanding of the geochemistry, decay properties, and ingrowth kinetics of radium and its decay product radionuclides Introduction New unconventional drilling technologies (horizontal drilling combined with hydraulic fracturing, called fracking ) are unlocking vast reserves of natural gas in the United States and around the world (1,2). The potential economic value of these reserves has stimulated a rapid globalization of the approach (3). However, the pace of proliferation of these practices has raised concerns about the potential for unintended and undesirable environmental impacts (4-9). One key environmental issue associated with unconventional drilling and hydraulic fracturing is the management of water resources and liquid wastes (flowback and produced fluids) (10-15). Of the environmental contaminants documented in hydraulic fracturing liquid wastes, naturally occurring radioactive materials (NORM) are of particular concern (16-18). Recent attention has focused on unintentional releases of radium (Ra) isotopes from wastewater treatment plants (19), which can arise from incomplete treatment of high ionic strength flowback and produced fluids (20). For example, breakthrough of untreated fluids at a waste treatment facility in central Pennsylvania (northeastern United States) led to Ra contamination in stream sediments measured to be a factor of

109 greater in radioactivity concentration than local background levels (19). The magnitude of the Ra contamination at this site prompted the plant operator to proceed with remediation of contaminated sediments in the surface water system (Blacklick Creek) impacted by the discharges (21). Thus, NORM contamination of local environments, arising from improper treatment and disposal of produced fluids, could emerge as an unintended consequence of hydraulic fracturing. Although the potential for local populations and workers to experience unhealthy exposures to NORM contained in such wastes is controversial (16), monitoring the radioactivity concentrations in these materials is critical to the development of effective waste management strategies and exposure assessments. However, few peer-reviewed reports are available that document levels of NORM in produced fluids. Of those available from the Marcellus Shale (the largest shale-gas formation in the United States), most report radioactivity concentrations of a single element Ra (22-25). The naturally occurring Ra isotopes of concern ( 226 Ra and 228 Ra) have been reported (in peer-reviewed literature) to exceed 670 Bq/L and 95 Bq/L, respectively, in produced fluids (22-25). However, little attention has been paid to other environmentally persistent alpha- and beta-emitting NORM such as uranium (U), thorium (Th), radon (Rn), bismuth (Bi), lead (Pb), and polonium (Po) isotopes (Figure 4-1). In reviewing a report of gross alpha levels in fluids from Marcellus Shale, we observed that reported Ra radioactivity concentrations were similar to maximum gross alpha levels (22), indicating that Ra had been selectively extracted into the liquid wastes, while alpha-emitting daughters remained insoluble under the geochemical conditions of the fluid extraction process. Given that Ra decay products had likely existed in a steady-state radioactive equilibrium with Ra isotopes in the solid shale-formation matrix for millions of years prior to drilling activities, these observations prompted us to explore the radioactive equilibrium relationships of Ra decay products in produced fluids, particularly for the longer-lived alpha-emitters, 228 Th (t1/2 = 1.91 years) and 210 Po (t1/2 = 138 days) (half-lives were extracted from the NuDat 2 Database) (26). As we reported previously, the chemical composition of fluids from the Marcellus Shale can interfere with the analysis of Ra isotopes by wet chemistry methods (24). 90

110 However, the physicochemical properties of select alpha-emitters ( 210 Po, 228 Th, and certain U isotopes) allow for chemical extraction and analysis by isotope dilution alpha spectrometry techniques. Thus, we developed a method to analyze alpha-emitting Po, Th, and U isotopes in produced fluids from the Marcellus Shale. Using this method (in systems closed to the release of gaseous radon), we found that estimates of total radioactivity in produced fluids based on Ra isotopes alone can underestimate the total radioactivity present due to the ingrowth of Ra decay-product radionuclides, a process that we demonstrate can be modeled using radioactive ingrowth equations (27). This model predicts that when produced fluids are sealed to the release of radon gas, the total radioactivity concentration of produced fluid can increase by a factor greater than five within the first 15 days following extraction due to the ingrowth of Ra decay products. Measurements of decay series radionuclides 210 Po and 228 Th in produced fluids from the Marcellus Shale presented here support these predictions. Thus, estimates of the radioactivity associated with hydraulic fracturing liquid wastes must include projections of ingrowth of decay product radionuclides in the natural uranium ( 238 U) and thorium ( 232 Th) decay series Methods General The State Hygienic Laboratory (SHL) at the University of Iowa is accredited by the U.S. National Environmental Laboratory Accreditation Program (NELAP). Standard operating procedures and quality assurance measures meet those established by NELAP. All chemical reagents used were ACS grade or higher. All radioactivity values were decay corrected to the reference date of 7 May 2013, 0800 hours (CST). All uncertainties, unless indicated, are standard uncertainties corresponding to one standard deviation of multiple measurements (28) Tracers and Standards All radioactive tracers were a) standard reference materials (SRMs) obtained from the U.S. National Institute of Standards and Technology (NIST), b) NIST-traceable certified reference materials (CRMs) obtained from Eckert & Ziegler Radioisotopes (E&Z) or Analytics, or c) SRMs obtained from the United Kingdom National Physical 91

111 Laboratory (NPL) Management Ltd. The following sources were used: a 3-L liquid Marinelli geometry (E&Z 93474), 210 Pb (E&Z 94643), nat U (E&Z CRM 92564), 232 U (E&Z CRM or E&Z 7432; certified in equilibrium with 228 Th), 230 Th (NIST SRM 4342A or Analytics ), 209 Po (NIST 4326 or E&Z CRM 92565), and multiline alpha-emitting sources (E&Z 91005, Analytics , and Amersham AMR.43) Sample Description A representative sample of produced fluids from northeastern Pennsylvania (24) was used for all of the following experiments. A 200-L drum of Marcellus Shale produced fluids was received at the SHL on 7 May The sample originated from a well that was horizontally drilled to a depth of 2,100 m and fractured with approximately 35,000 m 3 of hydraulic fracturing fluid in early Analysts at SHL characterized the elemental composition using standard techniques High Purity Germanium (HPGe) Gamma Spectrometry HPGe gamma spectrometry of produced fluids was conducted as previously described (24). Briefly, we calibrated our detector to a 3-L liquid Marinelli geometry (E&Z 93474) using standard practices. To calibrate for the low energy gamma emission of 210 Pb, we counted a 3-L Marinelli beaker spiked with 210 Pb of known activity (E&Z 94643). This spectrum was merged with the detector calibration using standard features available in ORTEC Gamma Vision (version 6.08, analysis engine Env32). Quality assurance and quality control (QA/QC) measures included weekly background counts, and linearity and efficiency checks collected three times per week. A 3-L sample was homogenized by heating with 51 g of Bacto Agar (BD ; Becton Dickinson) and allowed to cool in a 3-L Marinelli beaker. The sample was then counted for 17 hr on a 30% efficient ORTEC HPGe. Spectral analysis was performed using ORTEC Gamma Vision (Version 6.08) with a library of radionuclides created in GammaVision Library Editor according to the manufacturer s recommendations. All emission energies, halflives (except for that of 209 Po), and their uncertainties were extracted from the NuDat 2 Database (26) and include evaluated nuclear data at the time of analysis. The sole exception was the half-life of 209 Po, for which we chose to use years (29). 92

112 Alpha-Emitting Radionuclides Analysis of produced fluids for alpha-particle emitting radionuclides in the 238 U and 232 Th decay series ( 210 Po, 228 Th, 230 Th, 234 U, 235 U, 238 U) was conducted by preconcentration and isotope dilution alpha spectrometry. All results presented are from an unfiltered subsample (20 L, in a polypropylene carboy) drawn from the homogenized 200-L barrel. Following each subsampling, the barrel was hermetically sealed. The subsample ph was adjusted to 2 and held (approximately 48 hr) to allow iron-rich particulate to dissolve to a transparent, yellowish acidified solution. Preconcentration and matrix simplification were then conducted via coprecipitation of Po, Th, and U with endogenous iron (Fe) as the hydroxide [Fe(OH)3] and added manganese (Mn) for coprecipitation as manganese dioxide (MnO2), as previously described (30, 31). Preliminary experiments demonstrated exceedingly low concentrations of 230 Th, allowing use of 230 Th as a radiotracer to determine yields and concentration of 228 Th. Following preconcentration and matrix simplification [via metal oxide/hydroxide co-precipitation; i.e., Fe(OH)3 and MnO2], Po, U, and Th were separated into radiochemically pure fractions via extraction chromatography MnO2 Coprecipitations Samples were spiked with mbq of 209 Po, 230 Th, 232 U, and nat U. After appropriate tracers were added, MnO2 coprecipitations were performed, based on published methods (33-35). Potassium permanganate (15 or 30 mg) and bromocresol purple (1 ml, 0.1%) were added to acidified (ph < 2) produced fluid (0.5 L) in glass beakers. The sample was diluted 2-fold in distilled water (dh2o), covered with a watch glass, and boiled (1 hr). The ph was adjusted to 7 8, and the sample was boiled for 1 hr and cooled overnight. Following the cooling period, the supernatant was aspirated; the remaining slurry (~ 50 ml) was transferred to a plastic conical tube (50 ml) and centrifuged (10 min), and the supernatant was discarded. Beakers were washed twice (5 ml 6 M HCl; 1 ml 1 M ascorbic acid), each time transferring the wash liquid to the 50- ml centrifuge tube to dissolve the MnO2 pellets. Centrifuge tubes were then gently heated in a water bath to fully dissolve the pellet and clarify the solution. 93

113 Method 1: SR Resin and Silver (Ag) Autodeposition Separation of Polonium In some cases, Po isotopes were isolated following an Eichrom method (30). Briefly, samples were spiked with 209 Po prior to MnO2 or Fe(OH)3 precipitation. Precipitates were dissolved (10 ml, 2 M HCl), reduced (1 ml, 1 M ascorbic acid), and gently heated in a water bath. Solutions were then loaded onto preconditioned Eichrom SR Resin (10 ml, 2 M HCl). Columns were rinsed (10 ml, 2 M HCl) to remove trace contaminants. Po was then eluted with two additions of acid [5 ml, 1 M nitric acid (HNO3); 15 ml, 0.1 M HNO3]. Eluent was wet ashed (0.5 M HCl) under low heat to remove HNO3. Samples were then dissolved (40 ml, 0.5 M HCl) and reduced (100 mg ascorbic acid). Po was then allowed to autodeposit overnight at 80 C onto Ag disks painted on one side with acid-resistant acrylic paint. Disks were then cleaned (~ 10 ml 0.5 M HCl, dh2o, ethanol, and acetone, in that order) and dried prior to alpha spectrometry Method 2: TRU-Ag-TEVA Separation (Final Method) After MnO2 coprecipitation and solubilization, most samples (Table 4-1) were loaded onto preconditioned TRU cartridges (10 ml, 4 M HCl; Eichrom) to adhere Po, U, and Th (32). TRU resin (Eichrom) was washed three times (5 ml, 4 M HCl) before eluting Po, U, and Th (10 ml, 0.1 M ammonium bioxalate) into 150-mL glass beakers containing approximately 20 ml of 0.1 M HCl. The eluent was then reduced to prevent interferences from iron (0.5 ml, 20% wt/vol hydroxylamine HCl; 0.1 ml, 1 M ascorbic acid) (36). Samples were incubated (90 C) in a double boiler on a stir plate. A magnetic stir bar and a polished Ag disk (one side coated with acid-resistant acrylic spray-paint) were placed into the beaker. After 2.5 hr, disks were removed and washed (10 ml each 0.1 M HCl, H2O, ethanol, and acetone, in that order). The remaining solution was taken to dryness and resuspended (10 ml, 4 M HCl). U and Th were then separated on a TEVA cartridge (Eichrom) using a method developed in our laboratory (37). The solution of 4 M HCl containing U and Th was loaded onto a preconditioned TEVA column (10 ml, 4 M HCl). Th does not adhere to the column in these conditions. Therefore, Th was collected in the eluent of the load solution along with an additional column wash (10 ml, 4 M HCl). The column was then washed (25 ml, 4 M HCl) to remove trace Th before U was eluted (5 ml, 0.1 M HCl). Th was precipitated by a rare-earth hydroxide as follows: 94

114 cerium (Ce; 30 μg), bromocresol purple (1 ml, 0.1%), and H2O2 (30 μl, 30%). The ph was adjusted to 7 with ammonium hydroxide and left undisturbed (30 min). U sources were prepared by a rare-earth fluoride precipitation by addition of Ce (50 μg), titanium trichloride (1 ml), and hydrofluoric acid (1 ml). U and Th samples were filtered on Eichrom Resolve Filters according to the manufacturer s recommendation. For a workflow schematic, see Appendix 2, Figure S Method 3: TRU-TEVA for Separation of U and Th Reported activities of U in the produced fluids were determined using a method previously developed in our laboratory (37). This method differs only slightly from those described above. Briefly, the pellets were dissolved in HNO3 (10 ml, 2 M) and TRU resin was preconditioned and washed with HNO3 (10 ml, 2 M) in lieu of HCl. This method was investigated but abandoned, as it does not allow for analysis of 210 Po Isotope Dilution Alpha Spectrometry All alpha sources were quantitated by standard isotope dilution techniques and counted in vacuum controlled α-spectrometers [Alpha Analyst (Canberra) or Alpha Ensemble (ORTEC)] as previously described (37). Briefly, source-to-detector distances were usually 10 mm, corresponding to a counting efficiency of approximately 18 30%. In some instances, the distance was increased to improve resolution. Radiochemical yields were determined by standard protocols using efficiencies calculated with a NIST traceable, multiline α-spectrometry standard source (E&Z or Analytics ). For all samples, thin films were used to prevent daughter recoil contamination of detectors (38). Sources were counted for hr, as necessary. Standard isotope dilution techniques were used to calculate the activity and recoveries of added controls. In samples where 232 U and 230 Th were used, activity of 228 Th introduced from the 232 U tracer was subtracted using yield determinations for Th isotopes calculated by 230 Th. QA/QC included blanks (no added tracers) and laboratory control spikes (LCS) Radioactive Ingrowth Modeling Radioactive ingrowth was modeled generally according to the Bateman equation (27) and solved in Microsoft Excel. The derivation and formatting of the Bateman equation was obtained from (39). 95

115 4.4. Results Radiochemical Disequilibria and Ingrowth Radiochemical yields for the final methodology were Po (81 ± 6%), U (63 ± 8%), and Th (85 ± 9%). The observed concentrations of natural U ( 238 U, 235 U, 234 U), and Th isotopes ( 234 Th, 232 Th, and 230 Th) were exceedingly low (< 5 mbq/l). These levels represented < 0.001% of the 226 Ra radioactivity concentration (670 ± 26 Bq/L; 186 kev peak) in the sample of produced fluids described previously (24). Similarly, we found that the radioactivity concentrations of Ra decay products, including 228 Th, 214 Pb, 214 Bi, 212 Pb, 210 Pb, 210 Po, and 208 Tl, were initially near detection limits (Figure 4-2A D, Tables 4-1 and 4-2; see Supplemental Material, Expanded methods, Polonium-210 ingrowth ). In contrast, subsequent analysis of the same sample of produced fluids over time revealed an increase in the radioactivity concentration of decay products 210 Po and 228 Th, which are supported by 226 Ra and 228 Ra, respectively (Figure 4-1; Figure 4-2A,B). Importantly, the storage drum was hermetically sealed between subsamplings for analysis of radioactive decay products to prevent the release of gaseous radon. Notably, under these conditions, the observed increase in radioactivity concentration of 210 Po and 228 Th followed an established radioactive ingrowth model (Bateman equation), which describes the ingrowth of decay products following a separation (radioactive disequilibrium) of decay products from the parent radionuclide at time zero (t0). From these observations we developed a theoretical model for the geochemical partitioning of NORM in the Marcellus Shale formation, within the context of hydraulic fracturing and associated waste disposal activities (Figure 4-3). This model serves as a guide for predicting the partitioning and radioactive ingrowth/decay of NORM in the environment surrounding unconventional drilling and hydraulic fracturing operations, as well as in the waste treatment and disposal setting. Importantly, the ultimate fate and transport of NORM in the surface and subsurface environment is site dependent and depends on the potential for release of radon gas; thus, the assessment of the ultimate fate and transport of NORM must be examined on an individual site basis. 96

116 4.5. Discussion Modeling the Partitioning NORM in Marcellus Shale The partitioning U and Th decay series radionuclides in Marcellus Shale liquid wastes is a function of elemental geochemical behavior linked with key biogeochemical features of the formation. Like many marine black shale formations, the Marcellus Shale is an ancient seabed that became enriched in U associated with organic matter (40, 17 ; 41). Produced fluids from the Marcellus Shale have characteristically high levels of salts, the origin of which has several explanations (42). There are notably low levels of sulfate (SO4 2 )(43), likely due to microbial processes that produce sulfides (S 2 )(44). The ionic strength, reducing environment, and low abundance of SO4 2 alter the potential for NORM to solubilize in produced fluids. For example, low levels of SO4 2 and relatively high ionic strength enhance the solubility of Ra, whereas reducing conditions promote precipitation of geochemical species of reduced U, that is, U(IV). Radium decay product radionuclides, such as Pb and Po, are also much more particle reactive and less likely to be extracted through the unconventional drilling and hydraulic fracturing process than decay-series parent Ra isotopes. Thus, differences in the speciation of the elements in the natural decay series govern the likely concentration that will be observed in liquid wastes (as they emerge from depth), following an unconventional drilling and hydraulic fracturing event Th Series Partitioning The parent and supporting isotope in the natural Th decay series, 232 Th (t1/2 = years), is not expected to undergo oxidation/reduction reactions under natural conditions at depth in the formation, but is nonetheless particle reactive and insoluble in environmental waters and brines (45). Accordingly, we observed exceedingly low concentrations of 232 Th in unfiltered Marcellus Shale produced fluids. However, the decay of 232 Th produces highly soluble divalent alkaline earth 228 Ra (t1/2 = 5.75 years), which has likely been in radioactive secular equilibrium (steady-state) with 232 Th for many millions of years (46). As a result, produced fluids are enriched in 228 Ra (relative to 232 Th), which is highly soluble in the high-salt-content brines that describe produced fluids. 228 Ra decays by beta emission to short-lived 228 Ac (actinium-228; t1/2 = 6.15 hr), which likely forms insoluble complexes and quickly adsorbs to mineral surfaces at 97

117 depth and decays rapidly to form highly insoluble alpha-particle emitting radionuclide 228 Th (t1/2 = 1.91 years) (47). Similar to other Th isotopes, 228 Th is insoluble in interstitial fluids of shale formations, and its concentration is also low in produced fluids as they emerge from depth. Notably, the large difference in solubility between 228 Ra and 228 Th gives rise to a chronometer that has the potential to determine the time when fluids were extracted from the Marcellus Shale (for more information, see Supplemental Material, Expanded methods, Thorium-228 ingrowth ). As 228 Th ingrows at a rate related to its half-life, its decay product 224 Ra (t1/2 = 3.63 days), rapidly ingrows to steady-state radioactive equilibrium. Rapid ingrowth of 224 Ra is followed by a series of short-lived radioactive decay products that ultimately decay to stable 208 Pb (Figure 4-1). Within this series of relatively short-lived decay products, gaseous 220 Rn (t1/2 = 55.6 sec) presents a potential challenge to modeling expected increases in total radioactivity resulting from radioactive ingrowth processes. In contrast, because the half-life of 220 Rn is so short, migration beyond the immediate vicinity of nuclear formation is likely minimal and disequilibrium is not expected. Thus, in this decay series, the modeled total 228 Rasupported radioactivity concentration in produced fluids has the potential to increase to a maximum within 5 years of extraction from the shale formation, followed by a decrease determined by the half-life of 228 Ra (t1/2 = 5.75 years) (Figure 4-4A,B). This suggests that inclusion of the ingrowth and decay of 228 Ra decay products (particularly 228 Th) is important for development of appropriate liquid waste management U Series Partitioning. Owing to the geologic history and reducing (anoxic) conditions at depth in the Marcellus Shale formation, parent and supporting radionuclide 238 U (which, unlike 232 Th, can be redox active under natural conditions) is likely to be contained in the crystal lattice of minerals or adsorbed to solid phase structures in a reduced highly insoluble (+4) oxidation state (41) (Figures 4-1 and 4-3). Thus, geochemical conditions favor adsorption of 238 U and decay-product actinides ( 234 Th, 234 Pa, and 234 U) to interstitial surfaces of surrounding minerals (Figures 4-1 and 4-3) (45), and these radionuclides are likely fixed at depth. In support of these assertions, we observed exceedingly low concentrations of U and Th radionuclides in unfiltered produced fluids from Marcellus Shale (Tables 4-1 and 4-2; see also Appendix 2, Uranium absent ). Analysis of alpha spectra further revealed 98

118 an apparent enrichment of 234 U (relative to 238 U) in produced fluids, which can likely be explained by alpha-recoil processes (Figure 4-2E,F) (48, 49). Further investigations of partitioning among relevant phases (filtered/ultrafiltered aqueous, particulate, and solid) will provide more detailed understanding of the speciation of actinides in unconventional drilling liquid wastes. In contrast to low solubility of 238 U-series actinides in produced fluids, 238 U decay product radionuclide 226 Ra (t1/2 = 1,600 years) is highly soluble in such fluids. Thus, 226 Ra becomes enriched in the aqueous phase at depth relative to supporting actinides, with which 226 Ra has likely been in secular equilibrium (steady state) for many millions of years (46). Decay product radionuclides of 226 Ra are concerning because of the long halflife of 226 Ra, which ensures natural production (via radioactive ingrowth) of decay products for thousands of years (Figure 4-4C F). Although 226 Ra is highly soluble in produced fluids, our observations suggest that 226 Ra decay product radionuclides (Figures 4-1 and 4-3) are relatively insoluble under these conditions and are retained at depth by interactions with mineral phases in the interstitial environment. Although this geochemical behavior results in a very low concentration of 226 Ra decay products as fluids emerge from depth, the Bateman radioactivity ingrowth equations predict that (in systems closed to the release of gaseous 222 Rn) the total 226 Ra-supported radioactivity concentration in produced fluids can increase by a factor > 5 (alpha-particle emissions by a factor of approximately 4) over a period of 15 days following extraction of produced fluids (Figure 4-4D). Importantly, radioactive ingrowth will continue for decades as longer-lived isotopes ( 210 Pb, t1/2 = 22 years; 210 Po, t1/2 = 138 days) approach radioactive equilibrium with 226 Ra (at a rate related to their own half-lives; Figure 4-4E). As an example, we compared the Bateman equation based radioactivity ingrowth model to the observed radioactivity concentration of alpha-emitting radionuclide 210 Po in sequential analyses of unfiltered, acidified produced fluids from Marcellus Shale that were stored in a hermetically sealed container for several months. The observed increase in radioactivity concentrations of 210 Po in this sample followed the predicted ingrowth under the conditions described (Figure 4-2A). Ingrowth of long-lived radioactive 210 Pb and 210 Po is important to overall risk assessments in this context because these radionuclides are potentially bioavailable and may accumulate in higher organisms (50-53). Thus, the use 99

119 of 226 Ra alone to predict total radioactivity concentration in liquid drilling wastes can underestimate the increase in levels that will occur over time and neglects the potential for the bioaccumulation of alpha- and beta-emitting decay product radionuclides in bacteria, plants, and higher organisms. Similar to the decay product scenario of Th-series Ra isotope 228 Ra, establishing radioactive equilibrium of decay product radionuclides with parent 226 Ra is potentially confounded by the presence of a gaseous isotope (i.e., 222 Rn, t1/2 = 3.82 days) in the decay series. Further, in this case the half-life of 222 Rn is sufficiently long to potentially promote migration and separation (disequilibrium) from parent 226 Ra in systems that are open to the atmosphere (e.g., containment ponds; Figure 4-3). In these cases, the modeled concentration of 226 Ra decay products will need to include an assessment of 222 Rn emanation and decay to accurately portray the total concentration in liquid drilling wastes and the impact of increased 222 Rn and decay products to surroundings Conclusion Previous reports that described the radioactivity concentration in flowback, produced fluids, and other materials associated with unconventional drilling and hydraulic fracturing focused on one element Ra. Our projections suggest that in systems closed to the release of gaseous Rn, estimates based solely on 226 Ra/ 228 Ra will underestimate the total activity present by a factor > 5 within 15 days following extraction as Ra decay product radionuclides ingrow. The level of radioactivity (in a closed 226 Ra decay product system) will continue to increase and reach a maximum approximately 100 years after extraction (Figure 4-4F). At this time, when the long-lived 210 Pb and its decay products have reached equilibrium with 226 Ra, the total radioactivity will have increased by a factor > 8. Although this projection assumes that losses of Rn and other geochemically derived disequilibria are negligible, the physical process of ingrowth begins again at any time of Ra separation (e.g., sulfate treatment at wastewater treatment plants), and the total activity unavoidably increases as decay product radionuclides ingrow. Thus, long-lived, environmentally persistent Ra decay products ( 228 Th, 210 Pb, 210 Po) should be considered carefully as government regulators and waste handlers assess the potential for radioactive contamination and exposures. 100

120 NORM is emerging as a contaminant of concern in hydraulic fracturing/unconventional drilling wastes, yet the extent of the hazard is currently unknown. Sound waste management strategies for both solid and liquid hydraulic fracturing and unconventional drilling waste should take into account the dynamic nature of radioactive materials. Methods designed to remove Ra from hydraulic fracturing waste may not remove Ra decay products because these elements (Ac, Th, Pb, Bi, Po isotopes) have fundamentally different physicochemical properties (11; 15). Future studies and risk assessments should include Ra decay products in assessing the potential for environmental contamination in recreational, agricultural, and residential areas, as well as in developing a more detailed understanding of the accumulation of these radionuclides in higher organisms Acknowledgements We acknowledge the staff and faculty at the University of Iowa State Hygienic Laboratory (SHL) for assisting us in this research. Funding for these experiments was provided by the U.S. Nuclear Regulatory Commission (NRC-HQ-12-G ) and by Environmental Management Solutions (contract EMS FP ). R.S. is employed by Quality Radioanalytical Support, and R.L. is employed by Radiochemistry Laboratory Basics. M.K.S. is a paid consultant for Speer Law Firm, PA, Kansas City, Missouri. The other authors declare they have no actual or potential competing financial interests. 101

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127 Figure 4-1 Natural thorium and uranium decay chains. Half-lives and decay information were obtained from the NuDat 2 Database (26). Abbreviations: d, days; h, hours; m, minutes; s, seconds; y, years. 108

128 Figure 4-2 Activity and alpha spectra of Po, Th, and U. (A) Theoretical Bateman model of 210 Pb ingrowth (blue) and 210 Po (red) given 226 Ra levels and a system closed to emanation of gaseous radon in produced fluids sample with our empirical data (black squares; error bars subsumed within boxes). (B) Theoretical Bateman model of 228 Th ingrowth (green) and 228 Ra decay (blue) given 228 Ra levels and a system closed to emanation of gaseous radon in produced fluids sample with our empirical data in black (error bars subsumed within boxes). (C) Representative Po alpha spectrum of 209 Po tracer (orange) and 210 Po (red). (D) Representative Th alpha spectrum of 230 Th tracer (purple), 228 Th (green), and 228 Th decay products (black). 232 Th was virtually undetectable by this method. (E) Activities of 238 U (purple), 235 U (black), and 234 U (orange) in produced fluids; error bars represent one standard deviation of the determined activity of multiple counts (n = 3). (F) Representative U alpha spectrum of 238 U (purple), 235 U (not labeled), 234 U (red), 232 U tracer (blue), and 232 U tracer decay products ( 228 Th green; others black). 109

129 Figure 4-3 Theoretical model of NORM partitioning and associated waste in Marcellus Shale based on HPGe gamma spectrometry and alpha spectrometry of produced fluids. Solid arrows indicate a radioactive decay or series of radioactive decays. Dashed arrows indicate a physical or chemical partitioning process. 110

130 Figure 4-4 Theoretical Bateman model of Ra decay product ingrowth and decay (system closed to release of gaseous radon) (A) 15 days after extraction for 228 Ra (green dots), associated alpha (red dashes), and total activity (blue); (B) 70 years after extraction for 228 Ra (green dots), associated alpha (red dashes), and total activity (blue); (C) 70 years after extraction for 226 Ra (purple), 228 Ra (green dots), associated alpha (red dashes), and total activity (blue); (D) 15 days after extraction for 226 Ra (purple), associated alpha (red dashes), and total activity (blue); (E) 70 years after extraction for 226 Ra (purple), associated alpha (red dashes), and total activity (blue); and (F) 5,000 years after extraction for 226 Ra (purple), associated alpha (red dashes), and total activity (blue). 111

131 Table 4-1 Activity, Recovery, and Separation Method for Select Radioisotopes Analyzed by Alpha Spectrometry of Produced Fluids. Isotope Activity Recovery Days c n Method (mbq/l) a (%) b d 210 Po 151 ± 3 42 ± ± ± ± ± ± ± ± ± Th 5750 ± ± ± ± ± ± U N/A 60 ± N/A 69 ± U 1.13 ± ± U 0.14 ± ± U 2.58 ± ± a reported as mbq/l ± standard deviation of multiple counts b reported as percent (%) tracer recovery ± standard deviation of multiple counts c after 8 a.m. on 7 May 2013 (CST) d 1 = Sr-Ag Autodeposition, 2 = TRU-Ag-TEVA, 3 = TRU-TEVA 112

132 Table 4-2 HPGe Gamma Spectrometry of Produced Fluids. Isotope Activity (Bq/L) CL (Bq/L) a,b Peaks (kev) 228 Ac 76± , Ra 21± Pb 2.4± Tl <CL c m Pa <CL Th <CL Ra 670± Pb 256± , 242, 580, Bi 235± , 1120,1238, 768, 934, 1385, 1583, Pb <CL K 10± a at time of acquisition 2:18 PM (CST) on 15 May 2013 b Critical level determined by the Currie Limit c activity less than critical level All Uncertainties are GammaVision generated counting uncertainties 113

133 CHAPTER 5: PARTITIONING OF NATURALLY-OCCURRING RADIONUCLIDES (NORM) IN MARCELLUS SHALE PRODUCED FLUIDS INFLUENCED BY CHEMICAL MATRIX A portion of this chapter was submitted for publication in Environmental Science: Processes and Impacts on 17 October, The author list and submitted title are as follows: Nelson, A.W.; Johns, A.J.; Eitrheim, E.S.; Knight, A.W.; Basile, M.; Bettis, E.A.; Schultz, M.K.; Forbes, T.Z. Partitioning of Naturally-Occurring Radionuclides (Norm) in Marcellus Shale Produced Fluids Influenced by Chemical Matrix Abstract Naturally-occurring radioactive materials (NORM) associated with unconventional drilling produced fluids from the Marcellus Shale have raised environmental concerns. Research into accumulation of NORM (particularly radium (Ra)) in sediment near wastewater treatment plants has provided mixed results. Some suggest ionic strength is a key factor in Ra accumulation; however, little supporting evidence is available. We investigated Ra accumulation in the environment through observational experiments of a Marcellus Shale fluid spill. We found no enrichment of Ra or other NORM (uranium (U), thorium (Th), lead (Pb), and polonium (Po) isotopes) over background levels. To elucidate the mechanism of this observation, we then performed radiochemical experiments with Marcellus Shale produced fluids. Ultrafiltration experiments indicated U, Th, and Po are particle reactive in Marcellus Shale produced fluids and Ra and Pb are soluble. Sediment partitioning experiments revealed that >99% of Ra does not adsorb to sediments in the presence of Marcellus Shale produced fluids. Further experiments indicated that although Ra adsorption is related to ionic strength, the concentrations of heavier alkaline earth metals (Ba, Sr) are stronger predictors of Ra solubility. Modelling studies of the fate of Ra in concentrated brine spills should consider the individual chemical components of brines in addition to bulk chemical parameters such as ionic strength. 114

134 5.2. Introduction The levels of radium (Ra) isotopes and other naturally-occurring radioactive materials (NORM) in flowback and produced fluids from the Marcellus Shale are an emerging environmental concern (1-9). Recent reports demonstrated that Marcellus Shale produced fluids from unconventional drilling are enriched in Ra isotopes ( 228 Ra, 226 Ra, 224 Ra) and devoid of most other long-lived NORM, such as certain U, Th, Pb and Po isotopes (1,9,10). To date, environmental monitoring of NORM has focused on the fate of Ra downstream of wastewater treatment plants (2,11). The observation that Ra accumulated nearly 200 times background downstream of one treatment plant in Pennsylvania (PA) resulted in some suggesting that NORM signatures are indicators of Marcellus Shale drilling wastes (2). Yet, investigations of Ra accumulation in sediments downstream of other wastewater treatment plants have indicated mixed results. For example, a study of five treatment facilities in PA found no appreciable enrichment of Ra in downstream sediments (11). The reason for the observed differences is unclear, in part due to the lack of research into the effect of produced fluid chemistry (such as ionic strength) on radionuclide fate and transport. One way to investigate the effect of produced fluid chemistry on Ra accumulation in the environment is through natural experiments, i.e., observing the levels of Ra accumulation after an uncontrolled spill of Marcellus Shale produced fluids. However, even a well-designed study may not accurately apportion the source of contaminants due to ongoing and legacy pollution from mixed sources (natural gas and coal extraction industries), legal settlements, and misinformation (12,13). One example that highlights these complications is a spill that occurred at Dunkard Creek, West Virginia (WV) (14). In 2009, Dunkard Creek s salinity a chemical parameter characteristic of both unconventional drilling and coal bed methane fluids spiked to extraordinarily high levels which caused a fish kill that stretched over forty miles (15). Some believe that the spill was the result of drilling waste overflowing from a coalmine shaft, but the etiology of the spill remains unclear to the general public (16,17). Laboratory-based partitioning studies can unveil additional information about the chemical behavior of NORM in produced fluids. Although such experiments may lack 115

135 generalizability, they provide clues about behavior of radioactive elements without the challenges of accounting for uncontrolled environmental inputs, radioactive decay, and decay product ingrowth. A wide body of literature exists on the effects of ionic strength on Ra adsorption and desorption from sediments (18-24). These studies show that Ra generally partitions through an ion exchange mechanism to the aqueous phase as ionic strength increases, yet most empirical data stops at ionic strengths comparable to those of seawater. Further, most studies have only explored the effects of ionic strength by considering concentration of Na with little attention to high molarities of alkaline earth metals (Mg, Ca, Sr, Ba). It is unclear whether these models are appropriate for Marcellus Shale produced fluids which may have ionic strengths up to 10 times that of seawater and levels of alkaline earth metals in the g/l range (8,9,25). Despite years of research into NORM, the current understanding of Ra chemistry in Marcellus Shale produced fluids is murky and the understanding of the chemical behavior of U, Th, Pb, and Po in these fluids is largely unexplored. In this study, we characterize the levels and equilibrium statuses of NORM in sediments upstream and downstream of the high salinity spill at Dunkard Creek. To understand the levels of NORM observed at the site, we then applied laboratory based radiochemical experiments. Radiotracers and ultrafiltration were applied to determine the partitioning of U, Th, Ra, Pb, and Po in Marcellus Shale produced fluids. We then applied sequential extraction and radiotracer techniques to determine the potential for Ra, Pb, and Po adsorption-desorption on a variety of sediment textures and mineral compositions. Next, we investigated the effect of ionic strength on Ra using a chemical matrix characteristic of Marcellus Shale fluids. Finally, we explored the role of exchangeable cations (Na, Mg, Ca, Sr, Ba) at a range of concentrations (0.01 M, 0.1 M, and 1 M) on the partitioning of Ra. Collectively, this report (1) cautions the use of Ra and NORM as indicators of unconventional drilling pollution and (2) suggests that Ra fate and transport modeling studies are need that consider the chemical composition of brine spills. 116

136 5.3. Experimental Detailed experimental procedures are provided in Appendix 3. Sediments were collected from the West Virginia Dunkard Creek in May Metals, inorganics, and organics were analyzed at the University of Iowa State Hygienic Laboratory (Table S3-1 of Appendix 3). U, Th, Ra, Pb, and Po isotopes in Dunkard Creek sediments were analyzed by previously described methods (Table S3-2 and Table S3-3 of Appendix 3) (1,5,26,27). Grain size, PXRD, and HRTEM were performed at the University of Iowa using standard techniques. Sequential extractions were based on previously published methods (28). In partitioning and sequential extraction experiments, 226 Ra was determined by 222 Rn emanation (5), 203 Pb by NaI gamma spectrometry based on standard laboratory methods (29), and nat U, nat Th, and 210 Po by preconcentration and alpha spectrometry (1,30) Results and Discussion Field Data Given the association of NORM with Marcellus Shale fluids and its suggested use as an indicator of Marcellus Shale waste, we expected to find an enrichment of NORM in sediments downstream of the discharge site (31,32). Analysis of U-series ( 238 U, 234 U, 226 Ra, 210 Pb, 210 Po) and Th-series ( 232 Th, 228 Th, 228 Ra, 224 Ra) radionuclides in sediments by alpha and gamma spectrometry indicated radioactivity concentrations in all samples were at background (Figure 5-1, Figure 5-2, Table S3-2 and Table S3-3 of Appendix 3) (33). We observed a slight enrichment of Ra isotopes, 210 Pb, and 210 Po over the actinide elements; however, this enrichment was at background levels and did not greatly increase downstream of the discharge site. Although high 226 Ra/ 238 U ratios can indicate drilling fluid contamination in solution (34), we attribute the high 226 Ra/ 238 U ration in the sediments to the solubility of U in oxidizing conditions (35). The disequilibrium of 226 Ra decay products, 210 Pb and 210 Po, relative to 226 Ra is likely due to 222 Rn gas escape and alpha-recoil processes (36,37). NORM levels at the site are similar to those downstream of five wastewater treatment plants in Pennsylvania that handle Marcellus Shale waste, as reported by Skalak et al. (2014) (11). Similarly, we did not 117

137 observe an enrichment of Ra isotopes as reported by Warner et al. (2013) at Blacklick Creek, Pennsylvania (2). We cannot exclude the possibility that Ra was removed as RaSO4 solids as it passed through the various mineshafts before spilling into Dunkard Creek nor that the wastes discharged from wastewater treatment plants are inherently different than the spill at Dunkard Creek (38,39). However, given the discrepancy in the literature on the potential for Ra from Marcellus Shale to accumulate in riparian environments, we probed deeper into the fundamental environmental radiochemistry of Marcellus Shale produced fluids NORM in Produced Fluids Very little is known about the concentrations of most NORM in Marcellus Shale fluids, and less information is available regarding NORM partitioning between aqueous and particulate phases. Several studies have developed a general understanding of how NORM levels in produced fluids change throughout the lifecycle of the unconventional drilling process (7-9). For example, Ra isotope concentrations steadily increase concurrently with the age of the well and concentration of total dissolved solids (TDS) and alkaline earth metals (7,8). In contrast, U levels have been reported to spike briefly at the beginning of the flowback stage and then decrease over time (10). Lastly, an analysis of late stage Marcellus Shale fluids by Nelson et al. (2015) reported U, Th, Pb, and Po isotopes were initially absent, but certain isotopes ( 228 Th, 210 Pb, 210 Po) increase until reaching steady-state equilibrium with supporting isotopes (1). Collectively, these reports provide important clues about the behavior of NORM within Marcellus Shale fluids at the point source, particularly at increased pressure, higher temperature, and altered redox conditions that occur in the subsurface environment. It is unclear how U, Th, Ra, Pb, and Po behave when produced fluids enter lowtemperature geochemical environments. Although we anticipate the majority of U and Th isotopes (with the exception of 228 Th) will remain at depth or be adsorbed to solid waste products (1), understanding the solubility of U and Th in Marcellus Shale fluids under surface conditions is important, particularly in cases where there are significant interactions between the waste forms. To understand the basic partitioning of U, Th, Ra, Pb, and Po in surface waters, we spiked homogenized Marcellus Shale produced fluids 118

138 with appropriate radiochemical tracers. Spiked fluids underwent ultrafiltration (0.1 μm) and particulate and aqueous phases were analyzed by alpha or gamma spectrometry. U, Th, and Po associated with the particulates (98%, 97% and >99%, respectively) and Ra and Pb remained in solution (99% and 97%, respectively) (Figure 5-3A). Low particle reactivity of Ra and Pb led us to probe the mineral composition of particulates and dissolved solids in the Marcellus Shale fluids. Powder X-ray diffraction (PXRD) of the solid evaporites from the produced fluids revealed the presence of halite salts containing predominately alkali and alkali earth cations (Figure 5-3B). The diffractogram of the Fe particulates include a relatively high background due to fluorescence, but the presence of two broad peaks suggests the presence of an amorphous Fe oxyhydroxide (Figure 5-3C). In addition, weaker reflections correspond to the mineral akaganeite (β-feo(oh, Cl)), which requires the presence of 1-9 wt% chloride in solution for formation of this phase to be favored over goethite and other Fe 3+ oxhydroxide species (40). Akaganeite is most commonly observed as a corrosion product in marine environments (41), but the high ionic strength of the flowback water contains concentrations of chloride to support the formation of akaganeite. The high-resolution transmission electron microscopy (HRTEM) image of the Fe particulates reveals the formation of bladed aggregates that are approximately nm in width (Fig 5-3D). Akaganeite has previously been reported to form elongated aggregates with longitudinal striations and are similar to the morphology of the Fe particulates obtained from the produced fluids (42,43). We attribute the low observed adsorption of Pb and Ra to the akaganeite and amorphous iron oxides to matrix effects, similarly as observed for ferrihydrite and goethite (20) Environmental Fate of NORM The gross levels of radionuclides in unconventional drilling wastes may be inappropriate for assessing environmental impact given the possibility for surface adsorption and sedimentation (28). To understand the fate of radionuclides introduced into the environment, it is important to determine partitioning within soil and colloidal phase reservoirs through sequential extraction experiments (28,44). We first applied this technique to determine 226 Ra concentrations in water-soluble, carbonate, Fe and Mn 119

139 oxides, organic, and strong acid-digestible residue fraction for the sediments from Dunkard Creek incubated with produced fluids. We incubated Dunkard Creek sediment collected from the discharge site (0 m) to simulate introduction of Marcellus Shale produced fluids into Dunkard Creek. 226 Ra was measured in each sequentially extracted fraction by 222 Rn emanation, to allow for accurate, tracer-level radiochemical experiments (Figure S3-1 of Appendix 3). Sequential extractions of 226 Ra (1 hour) indicated >90% of 226 Ra remained in the load solution (Marcellus produced fluids) and nearly all the residual 226 Ra (>99%) was removed in the water-exchangeable fractions (Fig. 5-4A). The high solubility differs from observations at Blacklick Creek which indicate significant fractions of Ra partition into insoluble phases (2). The role of kinetics on the observed solubility was investigated in a time dependence study, where we performed the same sequential extraction experiment for 168 hours (one week) instead of 1 hour. The same trend occurred in the extended reaction time, with >90% of 226 Ra removed in the load solution and residual 226 Ra was observed in the remaining water-exchangeable fractions such that >99% was recovered. This result suggests that kinetics have minimal effects on Ra adsorption-desorption in this system, which is in agreement with other studies that find Ra adsorption to sediments occurs within minutes (18,21). We further investigated the mineralogy and soil characteristics of Dunkard Creek sediments, because both characteristics greatly affect the speciation and adsorption of Ra (28,45). Soil texture and PXRD analysis indicated that the discharge area sediment is loam primarily consisting of quartz (Figure S3-2 of Appendix 3). Given that loams have lower binding capacity for 226 Ra than clay-rich soils (19,20), we performed the sequential leaching on a variety of soils (Fig. S3-3 and Fig. S3-4 of Appendix 3). Regardless of soil type, the same relationship was observed that >90% of Ra remained in the load solution and nearly all the remaining 226 Ra was removed in the water exchangeable fractions. This suggested to us that some chemical parameter(s) of the Marcellus Shale produced fluids overwhelm the binding capacity of soil minerals. We suspected the high ionic strength in Marcellus Shale produced fluids could be responsible for the low Ra adsorption in this system; therefore, we tested Ra adsorption to Dunkard Creek sediments with variable ionic strengths. A surrogate matrix comprised 120

140 of the same chemical parameters as Marcellus Shale produced fluids (ionic strength = 4.4 M) was adjusted by serial dilution (1:1, 1:10, 1:100, 1:1000, and 1:10000) and spiked with a known amount of 226 Ra (37 Bq per sample). Sediments incubated with dilute surrogate (0.044 M and less) retained nearly all the 226 Ra (>97%), which agrees with many studies that show 226 Ra is particle reactive at ionic strengths typical of groundwater and freshwater (Figure 5-4B). However, at an ionic strength of 0.44 M (slightly less than a typical seawater of 0.7 M), 70% of 226 Ra remained in the aqueous phase (Figure 5-4B). Sediments incubated with undiluted surrogate matrix (4.4 M) retained 2% the 226 Ra (Figure 5-4B). Although Webster et al. (1995) have shown that seawater can solubilize approximately 10-25% 226 Ra (18), the high solubility of 226 Ra at ionic strengths less than seawater prompted us to probe deeper into the role of chemical composition of the produced fluids plays on the adsorption process. The chemical matrix of Marcellus Shale produced fluids is dominated by Na +, Mg 2+, Ca 2+, Sr 2+, and Ba 2+ cations and Cl - anions (8,9). Thus, we tested the effects of individual ions on competition with Ra 2+ for adsorption sites in Dunkard Creek sediments. We incubated sediments with solutions of chloride salts (0.01 M, 0.1 M, and 1 M), resulting in ionic strengths of 0.01 M, 0.1 M, and 1 M for Na solutions and 0.03 M, 0.3 M, and 3 M for alkaline earth solutions. Two clear trends emerged: (1) as cation concentration (and thus ionic strength) increased, the amount of 226 Ra 2+ in solution increased; and (2) as the ionic radius of the cation increased, the amount of 226 Ra 2+ in solution increased (Figure 5-4C). The effect of concentrations of Ba 2+ is quite dramatic, even at concentrations as low as 10 mm (typical Ba 2+ concentration of late-stage Marcellus Shale produced fluids (8)). Importantly, samples of relatively low ionic strength but considerable levels of Ba 2+, may not behave as expected based on ionic strength alone. These experiments suggest that in the event of a spill, Ba 2+ in Marcellus Shale produced fluids will compete for Ra 2+ adsorption sites until the produced fluids have substantially diluted (Figure 5-5). Two inferences from the observed Ba 2+ competition are (1) Ra 2+ will not predictably bind to sediments downstream of Marcellus Shale produced fluid spills, thereby negating its utility as a tracer of Marcellus Shale pollution, and (2) Ra 2+ will likely travel many miles further through natural systems than otherwise predicted by the ionic strength of the solution. Thus, accurate measurement of 121

141 Ba 2+ concentration in produced fluids is more important than ionic strength when assessing treatment goals and potential environmental impact. Fate and transport of 226 Ra decay products, 210 Pb and 210 Po, from Marcellus Shale produced fluids are important to consider as these isotopes are well-known to bioaccumulate (46). 210 Pb is challenging to study in environmental systems due to its radiochemical properties. Similarly, 210 Po is often neglected as specific instrumentation and chemical separations (alpha spectrometry and autodeposition) are required for its analysis. Thus instead of measuring 210 Pb, we employed a cyclotron-produced isotope 203 Pb. The short half-life of 203 Pb (51.92 hour) makes this isotope effectively a massless tracer and more representative than stable Pb tracers when investigating the fate of naturally-occurring low-mass-abundance, radioactive Pb isotopes. Sequential extraction experiments were also performed for 203 Pb and 210 Po utilizing similar process described above. Results for 203 Pb indicated that 45 ± 2% of 203 Pb remained in the produced fluids (Figure 5-4D). The remainder of the 203 Pb was removed in the carbonate or strong acid phases (25 ± 1% and 17 ± 1%, respectively). Isotope-dilution alpha spectrometry indicated that 210 Po (traced with 209 Po) largely associated with carbonate and strong acid (25 ± 4% and 52± 2 %, respectively) phases (Figure 5-4D). These results to demonstrate that 210 Pb and 210 Po have different environmental fate and transport processes that may lead to radiochemical disequilibrium (non-steady state). More work is needed to understand the potential for these isotopes to migrate through the environment. In 2009, high levels of salinity were recorded in Dunkard Creek, which some suggested was the result of release of Marcellus Shale drilling wastes (16,17). Because NORM was previously suggested as an indicator of Marcellus Shale pollution (2), we expected to find high levels of natural Ra isotopes near the discharge site. However, sediment samples collected from the field site indicated that 226 Ra and other NORM levels were at background. Radiochemical partitioning experiments suggested that if produced fluids containing high levels of Ra 2+ had indeed spilled into Dunkard Creek, the high levels of Ba 2+ in Marcellus Shale produced fluids would have prevented Ra 2+ adsorption to sediments. Ra 2+ would have traveled many miles down Dunkard Creek, 122

142 slowly depositing into creek sediments along the way rather than immediately depositing at the discharge site. Although environmental monitoring can piece together information about the origins of some pollution sources, without a firm understanding of the basic chemistry of produced fluids, elucidating the etiology of spills from the extractive industries will remain challenging. Formation signatures are often used as an attempt to apportion waste sources; however, our experiments suggest that the use Ra (or Ra isotope ratios) as an indicator of unconventional drilling activity is inappropriate. Further, without a fundamental understanding of the behavior of NORM in extreme chemical matrices, such as Marcellus Shale drilling wastes, accurate assessments of environmental impacts and dose reconstructions may be difficult to near-impossible to achieve. More research is needed that addresses the mobility of NORM throughout the lifecycle of the well. Future studies should address the effects of local geology and hydraulic fracturing chemical additives on the fate and transport of NORM Acknowledgements The authors would like to acknowledge Dustin May, Marinea Mehrhoff, Mengshi Li, Michael Wichman, Adam Ward, and Sylvia Joun Lee, for their support. This research was partially supported by NSF Grant# EAR for the Critical Zone Observatory for Intensively Managed Landscapes (IML-CZO), the Center for Health Effects of Environmental Contamination (CHEEC) at the University of Iowa, and the Center for Global and Regional Environmental Research (CGRER) at the University of Iowa. M.K.S. is a paid consultant for Speer Law Firm, PA, Kansas City, Missouri. The other authors declare they have no actual or potential competing financial interests. 123

143 5.6. References 1. Nelson, A. W.; Eitrheim, E. S.; Knight, A. W.; May, D.; Mehrhoff, M. A.; Shannon, R.; Litman, R.; Burnett, W. C.; Forbes, T. Z.; Schultz, M. K. Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale. Environ. Health Perspect. 2015, 123 (7), Warner, N. R.; Christie, C. A.; Jackson, R. B.; Vengosh, A. Impacts of shale gas wastewater disposal on water quality in western Pennsylvania. Environ. Sci. Technol. 2013, 47 (20), Zhang, T.; Gregory, K.; Hammack, R. W.; Vidic, R. D. Co-precipitation of Radium with Barium and Strontium Sulfate and Its Impact on the Fate of Radium during Treatment of Produced Water from Unconventional Gas Extraction. Environ. Sci. Technol. 2014, 48 (8), Zhang, T.; Bain, D.; Hammack, R.; Vidic, R. D. Analysis of Radium-226 in High Salinity Wastewater from Unconventional Gas Extraction by Inductively Coupled Plasma-Mass Spectrometry. Environ. Sci. Technol. 2015, 49 (5), Nelson, A. W.; May, D.; Knight, A. W.; Eitrheim, E. S.; Mehrhoff, M.; Shannon, R.; Litman, R.; Schultz, M. K. Matrix Complications in the Determination of Radium Levels in Hydraulic Fracturing Flowback Water from Marcellus Shale. Environ. Sci. Technol. Lett. 2014, 1, (3), Brown, V. Radionuclides in fracking wastewater: managing a toxic blend. Environ. Health Perspect. 2014, 122, A50-A Rowan, E.; Engle, M.; Kirby, C.; Kraemer, T. Radium Content of Oil- and Gas-Field Produced Waters in the Northern Appalachian Basin (USA): Summary and Discussion of Data Sci. Invest. Rep. (U.S. Geol. Surv.) 2011, 5135, Haluszczak, L. O.; Rose, A. W.; Kump, L. R. Geochemical evaluation of flowback brine from Marcellus gas wells in Pennsylvania, USA. Appl. Geochem. 2013, 28 (0),

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146 27. Schultz, M.; Burnett, W.; Hinton, T.; Alberts, J.; Takacs, M. Analysis of Am, Pu and Th in Large Volume Water Samples in the Presence of High Concentrations of Iron. In Environmental Radiochemical Analysis II; Warwick, P.; Royal Society of Chemistry Publishing: Cambridge, 2003; pp Schultz, M.; Burnett, W.; Inn, K.; Thomas, J.; Lin, Z. NIST SPECIATION WORKSHOP Gaithersburg, MD June 13-15, J. R. Natl. Inst. Stand. Technol. 1996, 101 (5), Knight, A. W.; Eitrheim, E. S.; Nelson, A. W.; Schultz, M. K. Model development for protactinium extraction from liquid-liquid systems in acidic conditions by (2,6)-dimethyl-4-heptanol. Nukleonika 2015 (accepted) 30. Knight, A. W.; Eitrheim, E. S.; Nelson, A. W.; Nelson, S.; Schultz, M. K. A simple-rapid method to separate uranium, thorium, and protactinium for U-series agedating of materials. J. Environ. Radioact. 2014, 134, Warner, N. R.; Jackson, R. B.; Darrah, T. H.; Osborn, S. G.; Down, A.; Zhao, K.; White, A.; Vengosh, A. Geochemical evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania. Proc. Nat. Acad. Sci. 2012, 109 (30), Warner, N. R.; Darrah, T. H.; Jackson, R. B.; Millot, R.; Kloppmann, W.; Vengosh, A. New Tracers Identify Hydraulic Fracturing Fluids and Accidental Releases from Oil and Gas Operations. Environ. Sci. Technol. 2014, 48 (21), Myrick, T.; Berven, B.; Haywood, F. State background-radiation levels: results of measurements taken during ; Oak Ridge National Laboratory: Oak Ridge, TN, Al-Masri, M.; Al-Akel, B.; Nashawani, A.; Amin, Y.; Khalifa, K.; Al-Ain, F. Transfer of 40K, 238U, 210Pb, and 210Po from soil to plant in various locations in south of Syria. J. Environ. Radioact. 2008, 99 (2), Maher, K.; Bargar, J. R.; Brown Jr, G. E., Environmental speciation of actinides. Inorg. Chem. 2012, 52 (7),

147 36. Moore, H. E.; Poet, S. E. 210Pb fluxes determined from 210Pb and 226Ra soil profiles. J. Geophys. Res. 1976, 81 (6), Fleischer, R. L. Isotopic disequilibrium of uranium: alpha-recoil damage and preferential solution effects. Science 1980, 207 (4434), Kondash, A. J.; Warner, N. R.; Lahav, O.; Vengosh, A. Radium and Barium Removal through Blending Hydraulic Fracturing Fluids with Acid Mine Drainage. Environ. Sci. Technol. 2013, 48 (2), He, C.; Zhang, T.; Vidic, R. D. Use of abandoned mine drainage for the development of unconventional gas resources. Disruptive Sci. Technol. 2013, 1 (4), Schwertmann, U.; Cornell, R. M., Akaganéite. In Iron Oxides in the Laboratory; Wiley-VCH Verlag GmbH: Weinheim, 2007; pp Refait, P.; Génin, J.-M. The mechanisms of oxidation of ferrous hydroxychloride β-fe2(oh)3cl in aqueous solution: The formation of akaganeite vs goethite. Corros. Sci. 1997, 39 (3), Holm, N. G. New evidence for a tubular structure of β-iron(iii) oxide hydroxide akaganéite. Origins Life Evol Biosphere 1985, 15 (2), Mohapatra, M.; Mohapatra, L.; Anand, S.; Mishra, B. K. One-pot synthesis of high surface area nano-akaganeite powder and its cation sorption behavior. J. Chem. Eng. Data 2010, 55, (4), Zhang, T.; Hammack, R. W.; Vidic, R. D. Fate of Radium in Marcellus Shale flowback water impoundments and assessment of associated health risks. Environ. Sci. Technol. 2015, DOI: /acs.est.5b Langmuir, D.; Riese, A. C. The thermodynamic properties of radium. Geochim. Cosmochim. Acta 1985, 49 (7),

148 46. Seiler, R. L.; Wiemels, J. L. Occurrence of 210Po and biological effects of low-level exposure: the need for research. Environ. Health Perspect. 2012, 120 (9),

149 Figure 5-1 Dunkard Creek, WV, sampling locations. Red circles indicate sediment sample locations. 130

150 Figure 5-2 Alpha and gamma spectrometry results for select samples near the discharge site at Dunkard Creek, WV. Mean activities (with standard deviations) of U (n=3), Th (n=2), Pb (n=3, measured by Po ingrowth), and Po (n=3) were measured by alpha spectrometry. Activities of Ra isotopes (n=1) were measured by HPGe gamma spectrometry, with counting uncertainties generated by GammaVision. 131

151 Figure 5-3 Particulate and aqueous radiochemistry of Marcellus Shale produced fluids. (A) Mean recoveries (with standard deviations) of U, Th, Ra, Pb, and Po in aqueous or particulate phases of radioisotope traced, filtered (0.1 μm) Marcellus Shale produced fluids. (B) pxrd spectrum of evaporated (low heat), filtered (0.1 μm) produced fluids. (C) pxrd spectrum of filtered (0.1 μm) produced fluid particulates. (D) TEM image of filtered (0.1 μm) produced fluid particulates. 132

152 Figure 5-4 Ra and Ra decay products partitioning in Dunkard Creek sediments. (A) Sequential extractions of Ra or Ba on select sediments: the first three bars represent mean recoveries with standard deviations of 226 Ra from sequential extractions by 222 Rn emanation; values from left to right indicate Ra removal from 11 different sediments (n=3), Dunkard Creek discharge site sediment (1 hour, n=3), Dunkard Creek discharge site sediment (168 hour, n=4). Fourth bar represents mean recovery with standard deviation of Ba (traced with 133 Ba) from Dunkard Creek discharge site sediment (n=3). (B) Aqueous fraction of surrogate fracturing matrix spiked with 226 Ra (37 Bq) and incubated with Dunkard Creek discharge site sediment at various ionic strengths; values represent means (n=3) with standard deviations subsumed within squares. (C) Aqueous fraction of Na, Mg, Ca, Sr, or Ba chloride salts (0.01, 0.1, and 1 M) spiked with 226 Ra (37 Bq) and incubated with Dunkard Creek discharge site sediment; values represent means (n=3) with standard deviations subsumed within squares. (D) Mean recovery with standard deviation of 203 Pb (n=3) and 210 Po (n=3, traced with 209 Po). 133

153 Figure 5-5 Theoretical depiction of Ba and Ra competition for adsorption on sediments in high and low Ba concentrations. 134

154 CHAPTER 6: CONCLUSIONS 6.1. Conclusions The work presented in the preceding chapters of thesis explored potential hazards associated with liquid wastes generated by unconventional drilling for natural gas by characterizing the chemistry and radiochemistry of naturally-occurring radioactive materials (NORM). The key findings from each chapter are summarized in subsequent text: 6.2. Chapter 1: Summary Hydraulic fracturing is not new, nor is the presence of NORM in wastes generated by natural gas operations. The combination of hydraulic fracturing and horizontal drilling (termed unconventional drilling ) emerged as a major technique for extracting natural gas from previously impractical geologic formations. The large volumes of wastes generated by unconventional wells have raised environmental concerns. One concern in particular is the presence of NORM in solid and liquid wastes from unconventional drilling operations. The chemistry and radiochemistry of each isotope and element of NORM is an important consideration for determining the risks associated with liquid, gaseous, or solid wastes generated by unconventional drilling Chapter 2: Summary NORM is ubiquitous in the environment and expected to occur in most ground waters, thus, detection of NORM in groundwater near hydraulic fracturing operations does not necessarily indicate that the NORM originated from any given hydraulic fracturing operation. Large-scale, longitudinal studies are needed to determine whether there is a risk for NORM associated with unconventional drilling to enter groundwater. Furthermore, such studies should include measurements of isotopic uranium ( 238 U and 234 U) and 226 Ra decay products ( 222 Rn, 210 Pb, and 210 Po) Chapter 3: Summary Naturally-occurring isotopes of Ra are elevated in unconventional drilling brines from the Marcellus Shale. Due to the elevated radioactivity, concentration measurements of Ra isotopes in these liquid wastes is important for informed waste management 135

155 decisions. However, precise measurements of Ra in these fluids are complicated by the presence of high levels of alkaline earth metals (principally Ba). Traditional wet chemical methods (including BaSO4 co-precipitation, MnO2 pre-concentration, and extraction chromatography) grossly underestimate the true activity of Ra isotopes in these fluids. This underestimation is likely due to competition between Ra and Ba for anions or binding sites. Precise measurement of Ra isotopes is obtainable by radon emanation or high purity germanium (HPGe) gamma spectrometry Chapter 4: Summary In addition to containing elevated levels of Ra isotopes, produced fluids from the Marcellus Shale have the potential to contain elevated levels of Ra supporting elements (U and Th isotopes) and Ra decay products (ex: Ac, Pb, Bi, and Po isotopes). A rapid separation and measurement method for pure, alpha-emitting isotopes (including isotopes of U, Th, and Po) was developed. Information collected during the method development process indicated that U, Th, and Po were initially absent from Marcellus Shale produced fluids. This suggests that U, Th, and Po are retained at depth (in the Marcellus Shale), owing to a variety of chemical mechanisms including redox chemistry. The absence of Ra decay products from Marcellus Shale produce fluids indicates that radiochemical ingrowth of Ra decay products must be considered for accurate environmental contamination and health risk assessments Chapter 5: Summary The high solubility of Ra in Marcellus Shale produced fluids has been attributed to the high ionic strength of these fluids. Investigations into the fate and transport of Ra associated with these fluids, found that as ionic strength increases the amount of Ra adsorption to riparian sediments decreases. Although the degree of Ra desorption was related to ionic strength, a stronger predictor for radium adsorption was the concentration of Ba present in the fluid. This suggests that for accurate predictions of the fate and transport of Ra released by Marcellus Shale produced fluid spills, models must consider the chemical composition of the spilled fluid. Traditional adsorption-desorption models based on sea water matrices may underestimate the amount of radium that partitions into the aqueous phase. 136

156 6.7. Future Directions The work presented in this thesis explored liquid wastes associated with unconventional drilling, with a focus on the Marcellus Shale. Several research questions remain with respect to liquid wastes. The behavior of NORM in solid wastes remains relatively unexplored Future Studies in Liquid Wastes. This thesis presents methods for detecting nat U, nat Th, nat Ra, and 210 Po in Marcellus Shale produced fluids. More work is necessary to detect 210 Pb in Marcellus Shale produced fluids. 210 Pb can be challenging to detect directly due to its low energy, low abundance gamma emissions. Thus, chemical separation approaches are necessary to detect 210 Pb in order to obtain lower limits of detection. One of the greatest challenges with chemical separation of 210 Pb is that there has historically been no convenient radiotracer for Pb isotopes. To address this challenges, experiments are currently underway that are exploring the use of cyclotron-produced 203 Pb Future Studies in Solid Wastes Thousands of kilograms of solid wastes (termed bit cuttings) are generated by unconventional drilling operations. Much of the solid waste is disposed at landfills near the drilling site; however, occasionally trucks will set-off radiation alarms at landfills. When the level of radioactivity in solid wastes exceed the allowable limit at a landfill, the trucks are diverted to other landfills (which may be hundreds of miles away). Apart from a few reports on the dose-rates from solid wastes, very little information is available to the scientific community on the isotopic profile of NORM in these materials. Furthermore, very little is known about the stability of NORM in these materials. Planned experiments will evaluate the isotopic composition of NORM in Marcellus Shale bit cuttings. Additionally, experiments are planned to assess the potential for NORM to leach from bit cuttings under conditions expected in landfills. Lastly, due to the connection between metal mobility and microbial communities, experiments are planned to determine how the microbial communities of bit cuttings change as they are exposed to conditions typical of landfills. 137

157 APPENDIX 1: SUPPLEMENTAL MATERIAL FOR CHAPTER 3 This appendix is supplementary material for Chapter 2 and was published on 10 February, This material is reprinted with permission. Please refer to: Nelson, A. W.; May, D.; Knight, A. W.; Eitrheim, E. S.; Mehrhoff, M.; Shannon, R.; Litman, R.; Schultz, M. K. Matrix Complications in the Determination of Radium Levels in Hydraulic Fracturing Flowback Water from Marcellus Shale. Environ. Sci. Technol. Lett. 2014, 1,

158 Table S1-1 Sample Matrix. analyte concentration (mg/l) detection limit (mg/l) method fluoride LOD a 0.1 fluoride, SM 4500-F C 18th chloride ± chloride, EPA bromide bromide, EPA sodium 29000± metals, EPA potassium 160± metals, EPA magnesium 850± metals, EPA calcium 13000± metals, EPA strontium 36000± metals, EPA barium 9000± metals, EPA manganese 3.4±0.2 1 metals, EPA iron 43±2 5 metals, EPA lead 1.0± metals, EPA aluminum LOD 5 metals, EPA silicon 3.7± silicon, EPA arsenic 0.81 b 0.01 metals, EPA sulfate LOD 40 sulfate, EPA nitrate nitrogen as n LOD 10 anions, EPA nitrite nitrogen as n LOD 5 anions, EPA ortho-phosphate as p 8± ortho-phosphate as P, LAC A alkalinity 10 c 1 alkalinity as CaCO3, SM 2320 B 18th bicarbonate alkalinity 10 c 1 alkalinity as CaCO3, SM 2320 B 18th carbonate alkalinity LOD c 1 alkalinity as CaCO3, SM 2320 B 18th total solids ± total solids (Dried at 103 Degrees C), SM 2540 B 18th total suspended solids 780±10 1 total suspended solids (dried at 103 degrees C) USGS gasoline 0.8± total extractable hydrocarbons, Iowa OA-2 mineral spirits LOD 0.1 total extractable hydrocarbons, Iowa OA-2 kerosene 0.2± total extractable hydrocarbons, Iowa OA-2 diesel fuel 1.3± total extractable hydrocarbons, Iowa OA-2 motor oil LOD 0.1 total extractable hydrocarbons, Iowa OA-2 total extractable hydrocarbons 2.3± total extractable hydrocarbons, Iowa OA-2 a below limit of detection b two measurements c one measurement 139

159 APPENDIX 2: SUPPLEMENTARY INFORMATION FOR CHAPTER 4 This appendix is supplementary information for Chapter 4 and was accepted for publication 11 March, 2015, published online on 2 April, 2015, and available in print on 1 July, This material is reprinted with permission. Note, that this material was published by the United States government and is therefore without copyright. Please refer to: Nelson, A. W.; Eitrheim, E. S.; Knight, A. W.; May, D. M.; Mehrhoff, M. A.; Shannon, R.; Litman, R.; Burnett, W. C.; Forbes, T. Z.; Schultz, M. K. Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale. Environ. Health Perspect. 2015, 123, S2.1. Expanded Methods S Polonium-210 In-Growth The long-lived 238 U (t1/2 = 4.5 x 10 9 years) in the formation supports the activity of 226 Ra, which then supports 210 Pb (t1/2 = 22.3 years) and 210 Po. Thus, these elements should be present (and of equal activity) in the Marcellus Shale. Given that 226 Ra was 670 Bq/L, we expected similar activities of 226 Ra decay products. Yet, when we directly measured 210 Pb by gamma spectrometry, its activity was below the critical level (Currie Limit, 14 Bq/L). We acknowledge this critical level may be unacceptably high for many applications. The high critical level is due to several reasons, first, the relatively high activity of Ra isotopes and decay products create a large Compton scatter, which buries the low energy peak of 210 Pb (46 kev, 4%) (1). Secondly, the high levels of ions in produced fluids attenuate gamma emissions thereby further reducing counting efficiency of the low intensity peak (2). Importantly, 210 Pb was not in secular equilibrium with its parent, 226 Ra, which led us to investigate the levels of 210 Po (the final radioactive species in the 238 U decay series). Similarly, experiments indicated 210 Po was not in secular equilibrium with either 226 Ra or 210 Pb. When we measured 210 Po levels ~2 months later, we noticed levels had increased approximately 450%. This in-growth, follows the theoretical Bateman equation with the assumption that all decay products of 226 Ra are initially absent (Figure 4-2A). 140

160 S Thorium-228 In-growth Initial experiments indicated that levels of thorium isotopes ( 232 Th, 230 Th, 228 Th) were negligible. Yet, over time the levels of 228 Th steadily increased. In this sample, 228 Th is supported by 228 Ra and its in-growth can be modeled on a transient equilibrium model (Figure 4-2B). Given that Th is generally insoluble in environmental waters (3) and in produced fluids Ra is soluble, the transient equilibrium model of 228 Ra/ 228 Th has the potential serve as a forensic tool to determine when samples removed from the Marcellus Shale (for up to ~ 10 years (4)). The 228 Ra/ 228 Th system provides key advantages over other tools including (1) the chemical disequilibrium introduced by the poor solubility of Th (2) the relative ease of measuring 228 Th and 228 Ra (via 228 Ac) and (3) the relatively short half-live of 228 Th (t1/2 = 1.9 years) that allows for a chronometer that may be used within a matter of weeks. S Uranium Absent In addition to Ra decay products, we investigated levels of 238 U, 235 U, and 234 U in the produced fluids. Although U is often analyzed by mass spectrometry, the method we developed provides the advantage of simultaneous determinations of multiple U, Po, and Th isotopes. Given the high level of 226 Ra ( 238 U decay product), we were surprised to find levels of U isotopes less than 5 mbq/l (n=4), which is nearly 5-log lower than the activity of 226 Ra (Figure 4-2). There are very few peer-reviewed reports of U activities in produced fluids; however, the notably lower levels of U compared to 226 Ra is similar to data from the PA Department of Environmental Protection (5). Our analysis indicates there is a slight enrichment of 234 U compared to 238 U ( 234 U/ 238 U = 2.3), which is common in groundwater and indicative of daughter recoil (6). 141

161 S2.2. Supplementary References 1. National Nuclear Data Center (NNDC) at Brookhaven National Laboratory. NuDat 2 Database. (accessed February 24, 2015). 2. Landsberger, S.; Brabec, C.; Canion, B.; Hashem, J.; Lu, C.; Millsap, D.; George, G. Determination of 226 Ra, 228 Ra and 210 Pb in NORM products from oil and gas exploration: Problems in activity underestimation due to the presence of metals and selfabsorption of photons. J. Environ. Radioact. 2013, 125, Kumar, A.; Singhal, R.; Rout, S.; Narayanan, U.; Karpe, R.; Ravi, P. Adsorption and kinetic behavior of uranium and thorium in seawater-sediment system. J. Radioanal. Nucl. Chem. 2013, 295, Schmidt, S; Cochran, J. Radium and radium-daughter nuclides in carbonates: a brief overview of strategies for determining chronologies. J Environ Radioact 2010, 101, Barbot, E.; Vidic, N.S.; Gregory, K.B.; Vidic, R.D. Spatial and temporal correlation of water quality parameters of produced waters from Devonian-age shale following hydraulic fracturing. Environ. Sci. Technol. 2013, 47, Osmond, J.; Cowart, J.; Ivanovich, M. Uranium isotopic disequilibrium in ground water as an indicator of anomalies. Intl J Appl Radiat and Isot 1983, 34,

162 Figure S2-1 Schematic of Rapid Separation of U, Th and Po. 143

163 Figure S2-2 Representative Alpha Spectra. Panels (A-D) are representative spectra collected by Method 1: TRU-Ag-TEVA: (A) polonium fraction without 209Po tracer, (B) polonium fraction with 209Po tracer, (C) thorium fraction without 230Th tracer, (D) thorium fraction with 230Th tracer. Panels (E-F) are representative spectra collected by Method 2: TRU-TEVA: (E) uranium fraction with 232U tracer linear scale, (F) uranium fraction with 232U tracer log scale. 144

164 APPENDIX 3: SUPPLMENTARY MATERIAL FOR CHAPTER 5 A portion of this material was submitted for publication in Environmental Science: Processes and Impacts on 17 October, The author list and submitted title are as follows: Nelson, A.W.; Johns, A.J.; Eitrheim, E.S.; Knight, A.W.; Basile, M.; Bettis, E.A.; Schultz, M.K.; Forbes, T.Z. Partitioning of Naturally-Occurring Radionuclides (Norm) in Marcellus Shale Produced Fluids Influenced by Chemical Matrix. S3.1. SI Materials and Methods S General All samples were collected from the West Virginia Fork of Dunkard Creek on 30 May, 2014 between 9:00 and 16:00. Samples were collected from downstream to upstream (Figure 5-1). Grab samples were collected and preserved as required for the analyses listed in (Table S3-3). All metals, inorganics, and organics, were analyzed at the SHL according to the guidelines established by the National Environmental Laboratory Accreditation Program (NELAP). For more information on the specific methods used for each analyte, refer to Nelson et al. (2014) (1). All HPGe spectrometry measurements were performed by the SHL (Table S3-2) (2). Alpha spectrometry, radon emanation, and all partitioning experiments were performed at the Interdisciplinary Radiochemistry Laboratory at the University of Iowa, Iowa City (Fig. 5-2, 5-3, 5-4, Table S3-1). All radioactivity concentrations are decay corrected to the reference date and time of 9:00 AM, 30 May 2014, unless otherwise specifically stated. All radionuclide half-lives and emission energies were abstracted from the National Nuclear Data Center at Brookhaven National Laboratory ( S HPGe Sediment After drying, sediments were sieved and pulverized (mortar and pestle). Homogenized sediments were then transferred to Marinelli beakers (0.5 L) and counted for 17 hours by HPGe. Analysis of radionuclides using standard methods (2). 145

165 S Polonium and Uranium Preconcentration After drying ( 3 days, 60 C), sediments were homogenized by sieving and pulverizing (mortar and pestle). Dried sediment (1 g, dry weight) was treated with appropriate alphaspectrometry tracers ( 209 Po, 100 mbq, Eckert and Ziegler 92565; 232 U, 50 mbq, Eckert and Ziegler 92403) and leached overnight with acid (10mL, 6 M HCl). Po and U were then preconcentrated by MnO2 precipitation and separated as described (2). S Thorium Preconcentration and Separation Dried homogenized sediments (2g) were leached with acid (6M HCl, 20 ml) and traced with 229 Th (50 mbq, NIST SRM 4328C). Th was then preconcentrated by cerium fluoride precipitation, separated on TEVA (Eichrom), and counted by alpha spectrometry similarly as described (3). S Lead-210 Values of 210 Pb shown in Figure 2A were determined for by ingrowth of 210 Po (traced with 209 Po) similarly as above for 209 Po, based on the methods previously described (4). S Alpha Spectrometry All sources were covered with thin films and counted for 200 hours or until recording at least 1000 counts of tracer (which ever came first). Alpha spectrometry was performed as previously described (5). All sources were counted in vacuum-controlled chambers (Alpha Analyst, Canberra, Meridan, CT, USA) containing passivated implanted planar silicon (PIPS, Canberra) detectors with an average distance to detector of ~10 mm. S Grain size Sediment grain-size distribution was analyzed using the pipette method with size fraction breaks at <2µ (clay), 2-20µ (fine silt), 20-50µ (coarse silt) and 50µ-2mm (sand) at the University of Iowa Quaternary Materials Laboratory (Fig S3-4). S PXRD Sediments, produced fluids fines (0.1 μm polypropylene filter), and produced fluids solid-state evaporites were prepared for power X-ray diffraction (PXRD) by mortar 146

166 and pestel (under acetone). Diffractograms were collected on a Bruker Advance Diffractometer equipped with CuKα radiation (λ = Å) and a LynxEye detector. Scans were performed from θ with a step size of 0.02 and collection time of 1 sec/step. Major mineral phases present in the solid samples were identified using the Bruker Eva software (Fig. S3-2, Fig. S3-3). S High Resolution Transmission Electron Microscopy Morphological features of the Fe particulates were determined using high resolution transmission electron microscopy (HRTEM) at the University of Iowa Central Microscopy Research Center (Fig. 5-3D). A 1 mg ml -1 colloidal suspension of the particulates was prepared in ultrapure water and sonicated for 30 min to improve dispersion. Holey carbon copper grids (Ted Pella, Inc 01824, UC-A on holey, 400 mesh Cu) were loaded with 5 µl aliquots of the suspension and evaporated to dryness in air. HRTEM investigations were carried out by a JOEL JEM 2100F equipped with a cold Schottky cathode, field emission gun, and operated at a 200 kv accelerating voltage. Gatan DigitalMicrograph software was utilized for image acquisition in congruency with an externally inserted Orius camera cooled to -25 ºC. S Flowback Filtration U, Th, Ra, Pb, Po 232 U (Eckert and Ziegler 92403), 228 Th (in 232 U tracer/endogenous), 226 Ra (endogenous), 203 Pb Lantheus Medical Imaging, Billerica, MA), and 210 Po (from 210 Pb source NPL A13959) were added to produced fluids (20 ml, except 226 Ra 35 ml), stirred (6-18 hours, room temperature, 220 RPM), and ultra-filtered (0.1 μm, filtration Resolve Eichrom). Filters and supernatant samples requiring analysis by alpha spectrometry were then traced with nat U (Eckert and Ziegler 92564), 230 Th (NIST SRM 4342A), or 209 Po (Eckert and Ziegler 92565) and prepared using methods previously described (2). 203 Pb samples were quantitated by NaI gamma spectrometry. 226 Ra samples were analyzed by RAD7 (Fig. 5-3A). S Sediment Sequential Extraction of Ra Selected homogenized sediments were placed into 50 ml conicals n=3, 3.5 g) (Fig. S3-1). Marcellus Shale produced fluids (35 ml) were added to each conical before shaking on a rotating table (1 hr, room temperature, 220 RPM). Conicals were then centrifuged (5 147

167 min, 3400 x g), the supernatant was transferred to clean vials (40 ml, glass VOC). To prevent foaming during counting by RAD7, anti-foam solution (Sigma, emulsion B, 1 ml 25%) was added to each vial before topping with dh2o and hermetically sealing. Ra was then sequentially extracted from sediment based on methods previously described (6). Briefly, sediment was treated three times with water-soluble-phase extractant (0.4 M MgCl2, ph 5.5), once with carbonate-phase extractant (1M NH4Ac in 25% v/v acetic acid), once with reducible-phase extractant (0.01 M NH2OH in 25% v/v acetic acid), once with organic-phase extractant (30% v/v H2O2, 0.02 M HNO3) and finally with aciddigestible phase (4 M HNO3). Extractions were performed at room temperature on a rotating table (1 hr, 220 RPM), each time centrifuging and transferring supernatant to clean glass vials (40 ml, VOC). Vials containing acetic acid, H2O2, or HNO3 were taken to complete dryness before topping with dh2o and hermetically sealing. Samples were held 30+ days to ensure secular equilibrium between 222 Rn and 226 Ra before counting by RAD7 (Durridge, Billerica, MA) as previously described (1). Assessment of adsorption kinetics was performed on DC6 sediment similarly as described above, yet samples were incubated with flowback and the extractants for 168 hours en lieu of 1 hour. S Sediment Sequential Extraction of Ba, Pb, Po Sediment (discharge site) was placed into conicals (50 ml, n=3, 2 g). Marcellus Shale produced fluids (20 ml) and radiotracers ( 133 Ba Eckert and Ziegler 6133, 203 Pb (Lantheus Medical Imaging), 210 Po (supported by 210 Pb, NPL A13959) traced with 209 Po Eckert and Ziegler 92565)) were added to each conical before shaking on a rotating table (1 hr, room temperature, 220 RPM). Conicals were then centrifuged (5 min, 3400 x g), the supernatant was transferred to clean liquid scintallation (LS) vials (20 ml, glass). LS vials were then counted by a well-type sodium iodide (NaI) detector (Ortec) and gammaemitting radionuclides were quantitated using standard radioactivity measurement techniques, similarly as described previously (7). Po was separated and quantitated using standard methods previously described (2). The radionuclides adsorbed to the sediment were then sequentially extracted based on methods described previously above (6). Extractions were performed at room temperature on a rotating table (1 hr, 220 RPM), each time centrifuging and transferring supernatant to clean glass vials (20 ml, LS) (Fig. 5-4A-B). 148

168 S Ionic Strength and Ra Partitioning All experiments investigating Ra partitioning were performed on DC6 sediment (n=3, 3.5 g), with the indicated salt solution (35 ml), and 226 Ra standard (37.3 Bq, NIST traceable standard, Eckert & Ziegler ). Marcellus Shale produced fluids surrogate matrix consisted of reagent grade (or higher) chloride form salts with the following concentrations: Na + (1300 mm), K + (4 mm), Mg 2+ (35 mm), Ca 2+ (320 mm), Sr 2+ (410 mm), Ba 2+ (66 mm), Fe 3+ (0.78 mm), Cl - (4100 mm). Separate select cations (Na +, Mg 2+, Ca 2+, Sr 2+, and Ba 2+ ) were prepared by serial dilution to the following concentrations: 1 M, 0.1 M, and 0.01 M. All samples were shaken on a rotating table (1 hour, room temperature, 220 RPM), centrifuged (3400 x g), and the supernatant was transferred to clean glass vials (40 ml, glass VOC). Anti-foaming solution (1 ml) was added to each vial before topping with anti-foam (1 ml), hermetically sealing (30+ days), and counting by RAD7 (Fig 5-4C-D). 149

169 S3.2. Supplementary References 1. Nelson, A. W.; May, D.; Knight, A. W.; Eitrheim, E. S.; Mehrhoff, M.; Shannon, R.; Litman, R.; Schultz, M. K. Matrix Complications in the Determination of Radium Levels in Hydraulic Fracturing Flowback Water from Marcellus Shale. Environ. Sci.Technol. Lett. 2014, 1 (3), Nelson, A. W.; Eitrheim, E. S.; Knight, A. W.; May, D.; Mehrhoff, M. A.; Shannon, R.; Litman, R.; Burnett, W. C.; Forbes, T. Z.; Schultz, M. K. Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale. Environ. Health Perspect. 2015, 123 (7), Schultz, M. K.; Burnett, W.; Hinton, T.; Alberts, J.; Takacs, M. Analysis of Am, Pu and Th in Large Volume Water Samples in the Presence of High Concentrations of Iron. In Environmental Radiochemical Analysis II; Warwick, P.; Royal Society of Chemistry Publishing: Cambridge, 2003; pp Nelson, A. W.; Knight, A. W.; Eitrheim, E. S.; Schultz, M. Monitoring radionuclides in subsurface drinking water sources near unconventional drilling operations: a pilot study. J. Environ. Radioact. 2014, 142, Knight, A. W.; Eitrheim, E. S.; Nelson, A. W.; Nelson, S.; Schultz, M. K. A simple-rapid method to separate uranium, thorium, and protactinium for U-series agedating of materials. J. Environ. Radioact. 2014, 134, Schultz, M. K.; Burnett, W.; Inn, K.; Thomas, J.; Lin, Z. NIST SPECIATION WORKSHOP Gaithersburg, MD June 13-15, J. R. Natl. Inst. Stand. Technol. 1996, 101 (5), Knight, A. W.; Eitrheim, E. S.; Nelson, A. W.; Schultz, M. K. Model development for protactinium extraction from liquid-liquid systems in acidic conditions by (2,6)-dimethyl-4-heptanol. Nukleonika 2015 (accepted) 150

170 Figure S3-1 General workflow for sequential extractions. 151

171 Figure S3-2 PXRD spectra for select sediments in Dunkard Creek. 152

172 Figure S3-3 PXRD of sediments from Quaternary Materials Laboratory at the University of Iowa. 153

173 Figure S3-4 Grain Size Triangle Plot of Sediments from Quaternary Materials Laboratory at the University of Iowa 154