Sampling and Analysis of Nanomaterials in the Environment: A State-of-the-Science Review Final Report R E S E A R C H A N D D E V E L O P M E N T EPA/600/R-08/098 September 2008 www.epa.gov Sampling and Analysis of Nanomaterials in the Environment: A State-of-the-Science Review Final Report Prepared for U.S. Environmental Protection Agency Office of Research and Development National Exposure Research Laboratory Environmental Sciences Division 944 E. Harmon Ave. Las Vegas, NV 89119 Prepared by Eastern Research Group, Inc. 10200 Alliance Road, Suite 190 Cincinnati, OH 45242 Scientific, Technical, Research, Engineering, and Modeling Support (STREAMS) Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade names and commercial products does not constitute endorsement or recommendation for use. U.S. Environmental Protection Agency Office of Research and Development Washington, DC 20460 3263cmb08 ii Notice The U.S. Environmental Protection Agency (U.S. EPA), through its Office of Research and Development (ORD), funded and managed the research described here. It has been subjected to the Agency’s peer and administrative review and has been approved for publication as an EPA document. iii iv Table of Contents Executive Summary.......................................................................................................................1 List of Acronyms............................................................................................................................2 1.0 Introduction and Scope of Review ..........................................................................................3 2.0 Information Search Strategy....................................................................................................4 2.1 Dialog® Search Strategy and Results.............................................................................4 2.1.1 Dialog® Search Parameters................................................................................5 2.1.2 Dialog® Search Procedure and Results..............................................................5 2.2 Targeted Search of Sources ...........................................................................................9 2.2.1 Nano-specific Journals.......................................................................................9 2.2.2 Conference Proceedings...................................................................................12 2.2.3 Databases of Nanotechnology Research..........................................................13 2.2.4 Grant Databases ...............................................................................................13 2.3 List of Contacted Researchers .....................................................................................14 2.4 Results of Literature Search and Potential Future Reviews.........................................15 3.0 Background............................................................................................................................23 3.1 Overview of Nanomaterials .........................................................................................23 3.1.1 Natural Nanomaterials .....................................................................................23 3.1.2 Anthropogenic Nanomaterials .........................................................................24 3.2 Overview of Environmental Transport ........................................................................27 3.2.1 Surface Water Transport..................................................................................27 3.2.2 Soil Transport...................................................................................................29 3.2.3 Groundwater Transport....................................................................................30 4.0 Sampling Techniques ............................................................................................................31 4.1 Sampling Techniques Suited for Surface Waters ........................................................32 4.2 Sampling Techniques Suited for Sediments ................................................................32 4.3 Sampling Techniques Suited for Soil ..........................................................................33 4.4 Sampling Techniques Suited for Groundwater............................................................34 4.5 Comparison of Sampling Techniques..........................................................................34 5.0 Analytical Techniques...........................................................................................................34 5.1 Analytical Techniques for Size Fractionation..............................................................36 5.2 Analytical Techniques for Size Distribution................................................................39 5.3 Analytical Techniques for Surface Area......................................................................42 5.4 Analytical Techniques for Direct Visualization ..........................................................43 5.5 Analytical Techniques for Phase and Structure...........................................................44 5.6 Analytical Techniques for Chemical Analysis ............................................................46 5.7 Comparison of Analytical Techniques.........................................................................51 6.0 Differentiation of Anthropogenic Nanomaterials..................................................................55 7.0 Summary................................................................................................................................55 v Table of Contents (continued) 8.0 References .............................................................................................................................57 Appendices Appendix A Dialog® Search Output vi Executive Summary This state-of-the-science review was undertaken to identify and assess currently available sampling and analysis methods to identify and quantify the occurrence of nanomaterials in the environment. The environmental and human health risks associated with nanomaterials are largely unknown, and methods needed to monitor the environmental occurrence of nanomaterials are very limited or nonexistent. Because this research is current and ongoing, much of the applicable information is found in gray literature (e.g., conference proceeding, communications with research scientists and other experts). The approach to this review included three separate strategies: • Collection of available published literature using Dialog®; • Review of information from targeted sources, such as nano-specific journals, conference proceedings, grants databases, and research databases; and • Contacts with industry and academic experts. This report summarizes the key characteristics that must be considered when collecting and analyzing samples in various environmental media. Based on results of the literature review, and personal communication with researchers, typical analytical methods and techniques that are currently used for nanomaterials are identified and briefly discussed. The review also identifies several sources that provided information on analytical techniques and equipment for nanomaterials. However, little information was obtained for sampling techniques that are specific for analysis of nanomaterials. Information obtained indicated that nanomaterial- specific sampling techniques have not yet been developed. Another area for which the search results provided little information is for differentiating anthropogenic (man-made) nanomaterials from natural nanomaterials. A number of potential sources that may provide additional information upon a more in-depth review were identified. As this report provides a current state- of-the-science review of active research topics at the time of writing, this report may require modifications as additional research is conducted. 1 LIST OF ACRONYMS Acronym Definition AAS Atomic Absorption Spectrometry AEM Analytical Electron Microscopy AES Atomic Emission Spectrometry AFM Atomic Force Microscopy BET Brunauer-Emmett-Teller method CBED Convergent Beam Electron Diffraction CCD Charged Coupled Device CE Capillary Electrophoresis DLS Dynamic Light Scattering EDS Energy Dispersive Spectroscopy EDX Energy-Dispersive X-ray Spectroscopy EELS Electron Energy Loss Spectroscopy EFTEM Energy-Filtered Transmission Electron Microscopy ESEM Environmental Scanning Electron Microscopy ETEM Environmental Transmission Electron Microscopy FFF Field-Flow Fractionation FLD Fluorescence Detector FlFFF Flow Field-Flow Fractionation GF Graphite Furnace HAADF High-Angle Annular Dark Field HPLC High-Performance Liquid Chromatography HR High Resolution ICP Inductively-Coupled Plasma LIBD Laser-Induced Breakdown Detection LC Liquid Chromatography MALLS Multi-Angle Laser Light Scattering MS Mass Spectrometry NMR Nuclear Magnetic Resonance RTM Resonant Tunneling Model SAED Selected-Area Electron Diffraction SAXS Small-Angle X-ray Scattering SEC Size Exclusion Chromatography SEM Scanning Electron Microscopy SIMS Secondary Ion Mass Spectrometry SPM Scanning Probe Microscopy STEM Scanning Transmission Electron Microscopy STM Scanning Tunneling Microscopy TEM Transmission Electron Microscopy TFF Tangential-Flow (cross-flow) Ultrafiltration UV Ultraviolet radiation XAS X-ray Absorption Spectroscopy