Measurement strategies for nanomaterials applicability to the environment

Transcription

1 Measurement strategies for nanomaterials applicability to the environment Raymond M. David, Ph.D., DABT Industry Consortium for Environmental Measurement of Nanomaterials (ICEMN)

2 Sources of exposure Engineered nanomaterials may be entering the environment from degradation of nano-enabled products, from degradation of waste from these products at the end of the life-cycle, and from waste materials generated during manufacturing.

3 The Problem Measurement methods and instrumentation are nonspecific can t distinguish between what is natural and what is engineered. The background levels of naturally occurring materials in the nanoscale are unknown. Background levels may vary greatly with location a job for USGS? Analytical sensitivity to measure ultra-low levels may not be available or only at the bench-level. Sample prep is a key. The Industry Consortium of Environmental Measurement of Nanomaterials (ICEMN) was formed to work with regulators to develop methods and support these measurements.

4 ICEMN what we did Our mission: to provide the California Department of Toxic Substances Control (DTSC) or other regulatory bodies information that could be used to measure nanoscale materials in air, surface water, and soil. To ascertain if methodologies used to identify, quantify, or characterize certain nanoscale materials in other media can be adapted to measurement in the environment. To establish collaborative activities with academic investigators/institutions that can provide expertise and/or research activities on the environmental measurement of certain nanoscale materials. To publish our views and strategies for regulatory scientists.

5 Special Issue of Environmental Engineering Science Perspective on what is addressed; what is a nanomaterial R. David, BASF Instrumentation challenges A. Salaman, PerkinElmer Measuring Nanomaterials in Food and Agriculture S. Bandyopadhyay, J.R. Peralta-Videa, J.L. Gardea-Torresdey, Univ. Texas El Paso Detection and measurement of engineered nanoparticles in natural waters A. Adeleye, S. Bennett, D. Zhou, J. Conway, K. Garner, A.A. Keller, U.C Santa Barbara Measurement Strategies of Airborne Nanomaterials M.L. Ostraat, J.W. Thornburg, Q.G.J. Malloy, RTI Nanomaterial Removal and Transformation During Biological Wastewater Treatment P. Westerhoff, A. Kiser, K. Hristovski, Arizona State, Univ. Oregon

6 Instrumentation Particle Size, Size Distribution, Surface Charge, Surface Area, Shape, Agglomeration, and Structure Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and Confocal Microscopy (CFM); Dynamic Light Scattering (DLS), Field Flow Fractionation (FFF), Molecular Gas Adsorption (BET), and Electrophoresis Particle Size. Concentration Inductively Coupled Plasma and Mass Spectroscopy (ICP- MS), Liquid Chromatography and Mass Spectroscopy (LC- MS), Ultraviolet/Visible Spectroscopy (UV/Vis), Fluorescence Spectroscopy (FL).

7 Instrumentation Composition Inductively Coupled Plasma and Mass Spectroscopy (ICP-MS) Liquid Chromatography and Mass Spectroscopy (LC-MS) Ultraviolet/Visible Spectroscopy (UV/Vis) Fluorescence Spectroscopy (FL) Thermogravimetry (TGA) Differential Scanning Calorimetry (DSC) Dynamic Mechanical Analysis (DMA) Fourier Transform Infrared Spectroscopy (FTIR) Raman Spectroscopy Each instrument has its limitations and biases

8 Air Airborne nanomaterials have the potential to impact environmental, public, and occupational health. Background and incidental airborne nanomaterials are ubiquitous.

9 Air Evaluating exposure to airborne nanomaterials poses challenges due to their small size, their negligible mass, and their high diffusivities. selection of appropriate dose metrics (mass, surface area, or number) identification of physico-chemical characteristics of nanomaterials that impact environmental and human health sampling strategies may be necessary to identify any spatial and temporal changes in nanomaterial concentration and physicochemical characteristics differentiating incidental and ENMs from background nanomaterials.

10 Air Exposure assessment and routine monitoring for airborne nanomaterials are either very minimal or nonexistent. Whenever monitoring efforts occur, they do not generally follow any consistent strategy. However, strategies to conduct exposure assessments have begun to emerge. Available strategies include: Long-term monitoring Area monitoring Pre/Post sampling Size resolved characterization

11 Instruments Portable aerosol photometers estimate mass concentration based upon an assumed density and particle size distribution (e.g., DustTrak, Model 8520, TSI Inc., Shoreview, MN; PDM-3 Miniram, Mie Inc., Bedford, MA). Condensation particle counter are real-time, single-particle counting instruments that grow particles to optically detectable sizes by condensing liquid onto the aerosol particles (e.g., CPC Model 3007 or P-Trak Model 8525, TSI Inc., Shoreview, MN). Diffusion chargers measure the SA of airborne nanoparticles by combining ions and particles into a single stream and detecting the electric current from charged particles (Nanoparticle surface area monitor, NSAM model 3550 or AeroTrak 9000, TSI Inc., Shoreview, MN or DC2000CE, EcoChem Analytics, League City, TX). Differential mobility analyzers classify particles based upon the ratio of their electrostatic and drag forces which are then detected with an optical particle counter (NanoScan SMPS Nanoparticle Sizer 3910, TSI Inc., Shoreview, MN) Cascade Impactors separate aerosol particles based upon the ratio of their inertial and drag forces and can also be used to collect samples on substrates for off-line analysis (Nano-Micro-Orifice Uniform Deposit Impactor (Nano-MOUDI) Model 125A, MSP Inc., Minneapolis, MN).

12 Wastewater ENMs will associate with bacterial biomass in WWTPs and will be removed when the biomass is removed (>90%). Tools, such as batch experiments with biomass or lab-scale reactors, appear effective for comparing relative removals of different types of ENMs -- could be used for screening purposes. Less information is available on ENM removal by WWTP unit processes that rely upon attached biofilms (e.g., trickling filters).

13 Surface water There is increasing potential for the release of nanomaterials into natural waters with increased production and applications. Although methods exist for lab-scale detection and measurement, few techniques are available for field or industrial applications. Exposure concentrations are generally predictable and vary with environmental compartment. Detection of NMs in natural waters is complicated by the presence of natural organic matter (NOM), electrolytes, bacteria, natural colloids, suspended materials and other constituents

14 Surface water Detection methods are limited to small-scale applications. ENMs are unique pollutants because they form a new discontinuous phase. Therefore, besides concentration, particle size, morphology, crystal structure, adsorbed macromolecules, surface charge, and agglomeration state are all relevant parameters to be determined.

15 Surface water Coupling two or more instruments is a common approach for ENM detection in natural waters. Size fractionation coupled with an element or isotope analyzer Size fractionation is possible with centrifugation, filtration, sizeexclusive chromatography, or field-flow fractionation. Elemental determination is possible with inductive coupled plasma-optical emission spectroscopy (ICP-OES) and gas or liquid chromatography. Flow field-flow fractionation (FFF) has been successfully coupled with inductively coupled plasma mass spectrometry (ICP-MS), UV-vis spectrophotometer, dynamic light scattering (DLS), to quantify silver NM, quantum dots, TiO 2, and fullerene.

16 Food and agricultural products Nanotechnology offers substantial prospects for the development of state-of-the-art products and applications for agriculture, water treatment, food production, food processing, preservation and packaging. The limitation for the detection and characterization of nanoparticles in complex matrices including soil, water and food, urged to develop efficient and sensitive detection techniques and develop new monitoring strategies for the future. The main challenges are the presence of artifacts caused by sample preparation, sample extraction, problems of separation between natural and engineered nanoparticles and lack of scientific reference materials.

17 Food and agricultural products Sample preparation separating the ENM from other media and suspending in a liquid for analysis. Instrumentation High performance Liquid Chromatography (HPLC) Ultra-Performance Liquid Chromatography (UPLC) Field Flow Fractionation (FFF) Capillary Electrophoresis (CE) Hydrodynamic chromatography (HDC) Size exclusion and ion-exchange chromatography

18 Common themes Sample preparation Background measurements Characterization of analytes Lack of instrumentation specificity/sensitivity for real-time measurement Laboratory-scale methodologies may not be practical for field work.

19 Special Issue of Environmental Engineering Science Perspective on what is addressed; what is a nanomaterial R. David, BASF Instrumentation challenges A. Salaman, PerkinElmer Measuring Nanomaterials in Food and Agriculture S. Bandyopadhyay, J.R. Peralta-Videa, J.L. Gardea-Torresdey, Univ. Texas El Paso Detection and measurement of engineered nanoparticles in natural waters A. Adeleye, S. Bennett, D. Zhou, J. Conway, K. Garner, A.A. Keller, U.C. Santa Barbara Measurement Strategies of Airborne Nanomaterials M.L. Ostraat, J.W. Thornburg, Q.G.J. Malloy, RTI Nanomaterial Removal and Transformation During Biological Wastewater Treatment P. Westerhoff, A. Kiser, K. Hristovski, Arizona State Univ., Univ. Oregon