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Research Programs: Contaminated Sediments
Research Areas: Predicting Residues
Contaminated Sediments
How to link chemical concentrations in water and sediment with tissue residues in aquatic and aquatic-dependent wildlife?
Background
A significant factor in EPA's deliberation about how to remediate a contaminated sediment site is the concentration of toxic chemicals likely to be found in the tissues of aquatic wildlife and aquatic-dependent wildlife. If the predictions of chemical residues in organisms are inaccurate, EPA might select options that require too much or too little remediation of the site relative to the actual risks posed to the environment and human health. Because remediation of contaminated sediments is often very expensive, EPA needs the predictions of chemical residues in tissues to be highly accurate and precise so that remediation of contaminated sites can be done most cost effectively.
The relationships between chemical concentrations in water and those in biota are defined as bioaccumulation factors (BAFs), and the relationships between chemical concentrations in sediment and those in biota are defined as biota-sediment accumulation factors (BSAFs). Bioaccumulation of persistent bioaccumulative toxicants (PBTs) in aquatic food webs (and hence BAFs and BSAFs) is a function of ecosystem properties and chemical properties.
Problem
No current approach enables non-bioaccumulation experts to readily understand the processes and conditions that control bioaccumulation of PBTs in aquatic food webs. Further, no approach adequately addresses the issues and uncertainties encountered when extrapolating bioaccumulation data across ecosystems, species, and time. Finally, the range of chemical and ecosystem properties that can be addressed (i.e., the chemical's rate of metabolism and hydrophobicity ( Kow ), ecosystem conditions of food web structure, organism trophic level, and sediment-water column concentration quotient ( Πsocw )) is narrow and should be broadened.
Approach
The research will develop a methodology to extrapolate bioaccumulation data (BAFs/BSAFs) across ecosystems, species, and time for PBTs and will demonstrate the applicability of BAFs/BSAFs for predicting ecological risks. Research will:
- Assemble high quality bioaccumulation data sets from Lake Michigan and existing Superfund sites;
- Use these data to develop a hybrid modeling/empirical extrapolation approach;
- Evaluate the hybrid approach in field situations for prediction deficiencies and biases; and
- Develop a software package that will perform the hybrid calculations.
