Environmental Forensics

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1 Environmental Forensics N O T E S Volume 4 28 Attention: Webinar Announcement Technical Approaches for Apportioning Liability and Allocating Environmental Costs December 1, 28 click here for more information F o r m o r e i n f o r m a t i o n o n E x p o n e n t s e n v i r o n m e n t a l s e r v i c e s, contact: Paul D. Boehm, Ph.D. Principal Scientist and Group Vice President, Environmental Group (978) pboehm@exponent.com Identification and Allocation of Polycyclic Aromatic Hydrocarbons (PAHs) By Paul Boehm, Ph.D. and Tarek Saba, Ph.D. This issue describes the most common fingerprinting techniques to identify the origin of PAH contamination and presents an innovative new application. Work on PAH source identification and liability allocation is based on a combination of techniques used over the past 2 years with more recent, detailed approaches applied to the ever-increasing complexity of contamination cases. This work is illustrated in a recent litigation case where identifying the PAH source to the sediment of an industrial waterway was a major deciding factor in the judge s assignment of cleanup costs for the sediment of a waterway Superfund site. Why PAHs? PAH compounds are typically implicated in environmental contamination cases as either contaminants of concern and/or drivers of remediation and natural resource damage claims. Because of their association with many industrial and municipal activities (e.g., refineries, smelters, former manufactured gas plants, coal-fired power plants, wastewater treatment, storm water runoff, oil spills) as well as their natural origin (oil seeps, erosion), PAHs are ubiquitous and are usually found as a result of mixtures of sources. Importantly, PAHs form part of the normal baseline or background contamination in industrial as well as many pristine areas. The background PAHs also reflect impacts from stationary and mobile combustion emissions, road runoff and sewer outfalls, and particulate from fires (ash and soot), among other sources. PAHs from regional activities like roadway and factory emissions and road runoff are typically deposited in urban soils and sediments, creating background or baseline PAHs, with concentration levels depending on the region. Thus, for proper assessment of PAH sources at a site, it is important to differentiate background PAHs from those originating in the site under investigation. This is where chemical fingerprinting can play an important role. 1

2 What are PAHs? PAHs are a class of organic compounds consisting of two or more fused benzene rings. PAHs most commonly encountered in the environment and analyzed as part of site investigations contain two to six fused rings. Naphthalene, consisting of two fused rings, is the simplest PAH (Figure 1). Benzo[a]pyrene is a 5-ringed PAH that was discovered to be carcinogenic in the early 193s. Naphthalene Figure 1. Some common PAH structures PAHs associated with lower formation temperatures (petroleum, petroleum fuels, and coals) often occur with straight chain hydrocarbons attached to the rings at one or more points. These PAHs are called branched or alkylated. In Figure 1, the straight chains are depicted as lines attached to the PAH with the end of the line representing a methyl group ( -CH 3 ). Thus, trimethyl naphthalene is also known as C3-naphthalene (Figure 1). PAH Sources Trimethyl naphthalene (C3-naphthalene) benzo[a]pyrene The most common pathways for PAH production include petrogenic and pyrogenic. Petrogenic PAHs are formed through slow, long-term, moderate temperatures (1 3 C), and are associated with fossil fuels (petroleum and coal). Pyrogenic PAHs are formed through rapid, high temperature combustion (>7 C) of motor (automobile), bunker (shipping), and power plant (coals and petroleum) fuels. Pyrogenic PAHs are also formed at intermediate temperatures (4 6 C) that are reached in the processing of coals into coal tars and coal tar products (e.g., creosote or coal tar pitch used in aluminum smelters). Formation temperatures are directly related to the types and complexities of PAHs formed (Lima et al. 25). Multi Component Environmental Forensic Investigations A case involving investigations of PAH sources usually includes several components: development of a site conceptual model, historical reconstruction of industrial activities, determination of all possible sources, analysis of existing PAH concentration data and geospatial distributions, collection of new data, assessment of transport pathways, chemical fingerprinting, statistical analyses, and source allocation. Chemical fingerprinting is a sophisticated cornerstone of most PAH cases, but seldom succeeds without the other lines of evidence. PAH Fingerprinting Methods Differentiation of Major PAH Source Types (Petrogenic versus Pyrogenic) The first important step, and sometimes the only step, is the differentiation of petrogenic PAHs from pyrogenic PAHs. What primarily differentiates the origins of the two major PAH classes is the formation temperature. During the generation of PAHs, the degree of alkylation in a given PAH assemblage is inversely proportional to the formation temperature. Thus, the characteristic PAH compositional profile of these different sources can be used to help distinguish among the different sources. Figure 2 shows an example of the alkylated PAHs formed at different temperatures within the naphthalene homologous series (C = naphthalene, C1 = methylnaphthalene, C2 = dimethyl naphthalene, etc.). This profile comparison can be used to define the origin of the PAH compounds (petrogenic versus pyrogenic). The basic step of separating these two major classes in a mixed assemblage of sources such as a sediment sample is a critical step in cases where the question is: how much of the PAH mass comes from a petroleum source as opposed to coal tar, smelters, diesel soot, and other pyrogenic sources? Methods for doing this have been established since the mid-198s (e.g., Boehm and Farrington 1984). RELATIVE ABUNDANCE Petrogenic Pyrogenic C C1 C2 C3 C4 C C1 C2 C3 C4 NUMBER OF ALKYL CARBONS Figure 2. Representative distribution of alkylated PAHs formed at different temperatures within the phenanthrene homologous series (C = phenanthrene) 2

3 In many cases, the PAH forensic chemist starts with existing data that were collected as part of a regulatory-based site investigation. Almost always, the 16 Priority Pollutant PAHs analyzed in a typical remedial investigation are inadequate for definitive fingerprinting. The example in Figure 3 shows the results from a petroleum sample analyzed for only the Priority Pollutant compounds, below the same sample analyzed for the extended PAH forensics lists, which are now standard in PAH source investigations. However using existing data as a first step, simple diagnostic PAH Priority Pollutant source ratios (the concentration of one PAH compound relative to another) have been proposed for screening of sediments (e.g., Budzinski et al. 1997). The ratios of four of the Priority Pollutants (phenanthrene/anthracene) and (fluoranthene/ pyrene) have both been used to begin the process of differentiation between sources (phenanthrene/anthracene > 1 signifies a probable petrogenic origin for the sample, while phenanthrene/anthracene < 1 indicates probable pyrogenic origin). Definitive PAH forensic investigations, however, need to go beyond such screening criteria. CONCENTRATION (ng/mg) 1,8 1,6 1,4 1,2 1, ,8 1,6 1,4 1,2 1, A. PAHs Full Analyte List CN C2N C4N ACE CF C2F CA C1P/A C3P/A CD C2D FLANT C1F/P C3F/P CC C2C C4C BKF BAP IND BGP B. EPA Priority Pollutant List CN C2N C4N ACE CF C2F CA C1P/A C3P/A CD C2D FLANT C1F/P C3F/P CC C2C C4C BKF BAP IND BGP Figure 3. Polycyclic aromatic hydrocarbon analyses of crude oil samples : A) Full parent and alkylated list (5 PAHs); B) Priority pollutant target PAH list (16 PAHs) Differentiation Between Petrogenic (Petroleum) Sources In oil spill, maritime, and other releases (e.g., Superfund) where two or more petroleum sources must be differentiated, techniques include the use of PAH compositional profiles, diagnostic ratios and double ratios, as well as the use of degradation-resistant markers of petroleum origin called geochemical biomarkers. In these cases is it important to obtain verifiable source samples and to take into account the weathering of petroleum that occurs after release. In cases where there is a question of whether the petroleum exclusion under CERCLA applies, such fingerprinting must include additional chemical compounds and elements to be able to determine if hazardous substances have been mixed with petroleum. In these cases, because petroleum and hazardous wastes at refineries, for example, contain many of the same constituents, it is the relative abundance (not the presence or absence) of these constituents that forms the backbone of the PAH forensic investigation. Differentiation Between Pyrogenic PAHs The cutting edge of PAH fingerprinting and source allocation exists in cases where the differentiation and allocation of two similar pyrogenic PAH sources is in question. Though the use of specific compound and compound ratios (see Boehm 26) exists in the toolkit of PAH forensic chemists, new chemical approaches have recently been applied to real cases, and have successfully and definitively been taken into court. The following is a recent example. Court Case: Allocation of PAH Contamination to the Sediments of the Hylebos Waterway The 1989 Record of Decision for the Hylebos Waterway, one of the Operating Units of the Commencement Bay Sediments Superfund Site, required the dredging of an area at the head of the waterway that was impacted by PAHs. This area is located in a region of the waterway where multiple potential sources are present, including wet scrubber sludge (WSS) and wastewater from a former aluminum smelter, creosote from dock pilings, storm water from roadways, and other combustion sources. In 25, the parties that were ordered to dredge the waterway filed a complaint for dredging cost contribution against the owner of a log sort yard with petroleum fuel use at the 3 3

4 yard and creosoted pilings under their loading dock and near the dredged area in question. The complaint alleged that the source of sediment contamination (petroleum and creosoted pilings) resulted from the operator of the log sort yard rather than discharges from the former aluminum smelter. The first phase of the investigation focused on identifying the source types in the sediments as petrogenic or pyrogenic. Through careful sampling of sediments and source candidates, and the analysis of samples for the PAH forensics list of analytes (i.e., alkylated PAHs), we concluded that the petroleum source materials present at the log sort yard were not detectable in the largely pyrogenic PAH assemblage in the sediments. Next, the challenge to application of PAH chemical fingerprinting in this case focused on the fact that the PAH source compositions (fingerprints) from the creosoted pilings (derived from coal refining) and the discharges from the smelter (related to coal tar pitch in the smelting process) are very similar. Also challenging was the lack of high quality chemical data characterizing the different PAH signatures from the former smelter, which required a heavy reliance on some of the existing historical chemical data. Using multiple lines of evidence, including but not limited to chemical fingerprinting approaches, we were able to characterize and find key diagnostic methods to differentiate the similar two main pyrogenic sources. For the aluminum smelter, the sludge from the WSS that was released from the smelter lagoons to the waterway had a highly variable fluoranthene/pyrene ratio. Thus, this commonly used diagnostic ratio could not distinguish between the different PAH sources. However, other diagnostic ratios including four Priority Pollutant PAHs, already existing in the available data sets (benz[a] anthracene/chrysene, BaA/CH) and (benzo[a]pyrene/ benzo[b]fluoranthene; BaP/BbF) were successful in separating the chemical fingerprints of smelter sludge from creosote (Figure 4). The use of this double ratio plot clearly grouped the samples associated with the former smelter operation with the sediment from the Hylebos, thus implicating the aluminum smelter as the major PAH source to the waterway sediment. Besides chemical fingerprinting, other lines of evidence supporting the apportionment included PAH concentration gradients in the sediment, bathymetric survey data for the waterway, historical discharges, and mass loading records. Though de minimus amounts of various sources cannot be excluded from the apportionment, all lines of evidence supported the conclusion that the PAH contamination was almost exclusively from the aluminum smelting WSS discharges and related air emissions, rather than the creosoted pilings. In 27, the court apportioned responsibility for 94 percent of the PAHs in the waterway sediment to the smelter sludge. BaP/BbF Figure 4. The ratios BaA/CH and BaP/BbF separates PAHs in creosote from PAHs in the aluminum smelter sludge References: Smelter Sludge and CO BaA/CH WSS in ditch Creosote piling WSS in the ponds Dredged sediment Creosote Piling Boehm, P.D., and J.W. Farrington Aspects of the polycyclic aromatic hydrocarbon geochemistry of recent sediments in the Georges Bank Region. Environ. Sci. Technol. 18: Boehm, P.D. 26. Polycyclic aromatic hydrocarbons (PAHs). Chapter 15. In: Environmental Forensics, Contaminant Specific Guide. R. Morrison and B. Murphy (eds.) Academic Press. Budzinski, H., I. Jones, L. Bellocq, C. Pierard, and P. Garrigues Evaluation of sediment contamination by polycyclic aeomatic hydrocarbons in the Gironde Estuary. Mar. Chem. Lima, A.C., J.W. Farrington, and C.M. Reddy. 25. Combustion-derived polycyclic aromatic hydrocarbons in the environment a review. Environ. Foren. Please contact Tarek Saba or Paul Boehm at Exponent if you would like additional information on this issue of our Environmental Forensics Notes. 4

5 Notice: Webinar Announcement Technical Approaches for Apportioning Liability and Allocating Environmental Costs December 1, 28 In Burlington Northern v US (7-191, 7-167), the Supreme Court has agreed this term to consider whether joint and several liability under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) can be avoided if a party demonstrates a reasonable basis to support divisibility under common law. The Court may set an evidentiary standard for the apportionment of liability under CERCLA 17. If this case broadens the opportunities to limit joint liability, a technically defensible environmental forensics evaluation could be a powerful component of an argument for divisibility. The Burlington Northern case serves as the basis for Exponent s technical webinar entitled Technical Approaches for Apportioning Liability and Allocating Environmental Costs. Central to Exponent s environmental expertise is a strong capability in environmental forensics. We have applied our expertise and experience to a wide variety of situations: refineries, former manufactured gas plants, mines, smelters, foundries, pulp and paper mills, wood treatment facilities, oil spills, fuel terminals, and many manufacturing facilities with contaminants in air, groundwater, surface water, sediment, and soil. We have more than 3 scientists and engineers with a variety of experience in environmental forensics. Click here for more information on our Environmental Forensics services. Click here to view our previous Environmental Perspectives Newsletters. The application of environmental forensics in litigations requires a technically sound and legally defensible approach at every step in the process from planning and analysis, through Daubert challenges and trial testimony. Click here to register. 5