Contents 1. Introduction ....................................................................................................... 1 2. Why use passive samplers? The advantages .................................................. 2 3. What passive samplers tell us ........................................................................... 5 4. Types of passive samplers ................................................................................ 7 5. Some theory on how passive samplers work .................................................... 9 6. Preparing, deploying, recovering, and storing passive samplers .....................11 7. Selecting passive samplers ............................................................................. 15 8. Analyzing passive sampler data ...................................................................... 15 9. Brief case study ............................................................................................... 19 10. Remaining scientific challenges in using passive samplers ............................ 20 11. US EPA contacts working with passive samplers ........................................... 22 12. Summary ......................................................................................................... 22 13. Acknowledgements ......................................................................................... 24 14. References used in this document ................................................................. 25 Appendix A ........................................................................................................... 29 Mention of trade names or commercial products in this document does not constitute the U.S. Environmental Protection Agency’s endorsement or recommendation for use. i Guidelines for Using Passive Samplers to Monitor Organic Contaminants at Superfund Sediment Sites 1. Introduction The objective of this Sediment Assessment and Monitoring Sheet (SAMS) is to provide introductory information on the use of passive samplers at Superfund sediment sites contaminated with hydrophobic organic contaminants. The concept of passive sampling in the environment was first developed in the 1980s, and samplers started to be deployed in the field for research purposes in the 1990s. Since then, passive samplers have been used for monitoring contaminant concentrations in the water column, soil and sediment interstitial waters, and air at sites around the world. Their use in sediments to date has been primarily for research, however. As discussed below, passive samplers are useful new tools for assessing contaminant exposures and evaluating the potential for adverse environmental effects at Superfund sites. After reading this SAMS, users will have a fundamental understanding of some common passive samplers and their potential applications at Superfund sites. This SAMS discusses passive samplers that can be used in both water column and sediment deployments, and in some cases both simultaneously. These passive samplers use polyethylene (PE), polyoxymethylene (POM), and solid phase micro-extraction (SPME) materials. Another type of passive sampler called semi-permeable membrane devices (SPMDs) have been used primarily in the water column as surrogates for biota such as fish, but will not be discussed here in any depth. When deployed together, passive samplers placed in the water column and in the sediment can provide information about contaminant gradients between the sediment and the water. For example, when an engineered cap is used as part of a site cleanup, passive samplers can be used as a monitoring tool to evaluate the contaminant flux from the underlying contaminated sediment, into the cap layers and into the overlying water. Passive samplers collect information about the dissolved concentrations of contaminants. The dissolved concentration is a useful measure of the amount of contaminant that is bioavailable to aquatic organisms. Passive samplers do not provide information about the concentrations of contaminants associated with bedded, suspended or colloidal particles in aquatic systems and therefore do not address directly the transport of contaminants associated with such particles. The focus of this document is on a subset of those contaminants of concern (COC) often found at Superfund sites that, chemically speaking, are known as the hydrophobic or nonionic organic chemicals. These include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated dioxins and furans (PCDD/Fs) and chlorinated pesticides such as DDT. These chemicals are particularly persistent in the environment and bioaccumulate in aquatic organisms, often drive the risks as Superfund sediment sites, and are the focus of this SAMS. Metal COC such as cadmium, copper, lead, mercury and zinc are not discussed. There is a growing scientific literature on using other types of passive samplers to monitor metals, but the field is not as established, and that work is beyond the scope of this SAMS. This document briefly discusses the use of passive samplers but does not provide specific protocols on deployment and recovery, nor does it describe the chemical analysis procedures for passive samplers (it is not a U.S. Environmental Protection Agency [EPA] standard method or operating procedure). However, with the increasing use of passive samplers at sites around the United States and the world, these types of specialized protocols and procedures are likely to be available in the near future. United States Office of Superfund Remediation and OSWER Directive 9200.1-110 FS Environmental Protection Technology Innovation, and December 2012 Agency Office of Research and Development 1 Guidelines for Using Passive Samplers to Monitor Organic Contaminants at Superfund Sediment Sites 2. Why Use Passive Samplers? The Advantages At Superfund sites, there often is the need to know the concentrations of hydrophobic organic contaminants in the water column and sediment interstitial water, and to understand the relationship between these levels and the total levels in the sediment (i.e., bulk sediment chemistry). Depending on the contaminant, there may be several ways to Information Box 1 Environmental phases are often measure these concentrations. The typical used to divide the aquatic environment into separate analytical methods are gas chromatography components, each with its own unique characteristics. with mass spectroscopy (GC/MS) or electron Understanding environmental phases and where a capture detection (GC/ECD) for most of the contaminant resides in these phases can assist in contaminants considered in this SAMS. These establishing whether the contaminants will be in a methods measure the quantity of these form resulting in exposure to aquatic organisms, wildlife and humans. Principal environmental phases contaminants in a selected matrix like water or important to contaminated sediment sites are defined sediment. However, before the analysis can be in Table 1. Definitions are generally based on the performed, it is necessary to collect the sample particle size or chemical qualities (e.g., sorption matrix and extract the contaminants from that strength of carbon types) of the substances making-up matrix. For the last 40 years, these hydrophobic the phase. Hydrophobic organic chemicals partition contaminants have been extracted from a between these environmental phases. In general, the volume of water or mass of sediment using majority of these contaminants will be associated with organic solvents. This conventional approach the particulate phase and are not typically readily has several disadvantages. First, for water bioavailable to result in an exposure. A portion of samples, even at the most contaminated sites, these contaminants will also associate with the colloidal and dissolved organic carbon (DOC) phases, contaminant concentrations are frequently so where they are also not readily bioavailable. Often the low that they are not detectable with the GC/MS least amount of contaminants will be in the truly or GC/ECD unless very large volumes of water dissolved phase, but this is the phase where they are (e.g., tens to thousands of liters) are extracted. the most readily bioavailable for exposure and uptake Furthermore, even when contaminants can be by organisms. detected, the results are often affected by Particulate sample artifacts like the presence of very small sediment particles, colloids and dissolved organic carbon (DOC), and thus the measured Dissolved Contaminant Truly concentrations do not represent the truly Organic of Dissolved Carbon Concern dissolved and bioavailable concentrations. These additional environmental phases (defined Information Box #1 Colloids in Table 1 and discussed in ) can result in overestimations of the dissolved The image above shows the partitioning of a concentrations in the water column and hydrophobic COC between the principal interstitial water. Second, for sediments, environmental phases, with the thickness of the solvent extraction removes nearly all of the arrows indicating the relative degree to which a contaminants from the sediment, including that contaminant associates with a given phase (based on Schwarzenbach and others (2003)). portion tightly bound or sequestered in the sediment matrix. While this type of information is useful for quantifying the total mass of United States Office of Superfund Remediation and OSWER Directive 9200.1-110 FS Environmental Protection Technology Innovation, and December