This seminar will feature Dr. Bruce Duncan, Senior Ecologist with EPA Region 10's Office of Environmental Assessment, and Dr. Jim Shine, Associate Professor of Aquatic Chemistry at Harvard University's Center for the Environment and part of the Harvard School of Public Health Superfund Research Program.
Dr. Duncan and EPA Region 10 have been assisting the NIEHS Superfund Research Program for many years. Part of recent support has been through the National Bioassay Project, a consortium of existing research centers focused on developing and crosswalking a suite of tests to evaluate complex mixtures in sediments. The consortium includes Texas A&M University, Duke University, Michigan State University, University of California - Davis, and University of California - San Diego with advice from the EPA Ecological Risk Assessors Forum.
As an ancillary to that project, detailed work on evaluating organism exposures to contaminants was conducted at a Superfund Site (Lower Duwamish Waterway) in Seattle, WA. A 2009 exposure study led largely by Matt Kelley (Texas A&M, now with LSU Health Sciences Center-Shreveport) and supported by EPA, Texas A&M, Southern California Coastal Water Research Project, and NOAA looked at the concordance between media concentrations, biomarker response, and bioaccumulation of PCBs and PAHs at several locations. Fish, mussels, and solid phase micro extraction devices (SPMEs) were placed in cages at two heights. SPMEs have been extracted for PAHs, PCBs, and pesticides. Sediment, water, mussels, and fish have been analyzed for PAHs and (except for water) are awaiting PCB analysis. In addition, mussel survival and growth were measured. The two vertical locations give some insight into the influence of the bottom sediment and contaminant flux from sediments on exposure at the sediment/water interface. The mussel accumulation and growth allow a field evaluation of concordance with SPMEs. Dr. Duncan's presentation will give an overview of this project.
Dr. Shine's presentation will focus on the "Gellyfish" sampling tool. The "Gellyfish", an in-situ equilibrium-based sampling tool for determining multiple free metal ion concentrations in aquatic systems, has been developed and refined under both laboratory and field conditions. The device is based on the equilibrium partitioning between free metal ions in the surrounding solution and iminodiacetate binding groups held within the gel matrix of the sampler. Ninety percent equilibration (t90) is achieved in approximately 26 hours. Apparent stability constants were measured for the binding of Cu, Zn, Pb, Ni, and Cd to the Gellyfish, allowing us to estimate their free metal ion concentrations in the surrounding solution. An accompanying computer model (GELLYMOD) was also developed to account for metal-metal competition for uptake into the sampler. Subsequent competition experiments involving two or three metals were performed to validate the computer model. The results suggested the use of the Gellyfish sampler, in conjunction with the model we developed, is a valid approach for accurately quantifying free metal ion levels in metal mixtures within environmentally relevant concentration ranges. Compared to other analytical methods for free metal ions, the Gellyfish sampler is inexpensive, rapid, reusable, easy to use, and can measure multiple metals simultaneously, thus permitting the generation of adequate quantities of data to examine spatial and temporal variability and other factors affecting metal speciation.