Application of Tools to Measure PCB Microbial Dechlorination and Flux into Water During In-situ Treatment of Sediments

This study addresses the Strategic Environmental Research and Development Program (SERDP) Statement of Need CUSON-06-03: Assessment and Measurement of Processes Impacting the Fate and Transport of Contaminants in Sediments. The needs addressed in this study are: 1) To develop and evaluate site characterization tools to measure the rates of important sediment chemical/physical/biological processes affecting the fate and transport of contaminants, and 2) To understand and quantify sediment exchange processes with overlying water. The project began in 2006; the report includes progress through December 2007 in this multi-year study. Our initial goals were to examine sediments from representative riverine and estuarine systems with well-characterized polychlorinated biphenyls (PCB) contamination histories. Since these sediments will be used for more detailed laboratory studies of dehalogenation, activated carbon (AC) amendments, and sediment-water exchange, a goal of the first year was to characterize the PCB levels and the presence of dehalogenating organisms. Only those sediments with sufficiently high PCB levels and active populations of dehalogenating microbes are suitable for subsequent experiments; results from these evaluations drive our initial go-no go decision. Results to date compare the PCB levels and availability across the sediment types. We have developed and calibrated a dynamic sediment-water exchange model of PCB transport that included particle coagulation and kinetically-limited partitioning. Overall hypothesis of this study is that the extent of biogeochemical reactivity and mobility of sedimentary contaminants is controlled by desorption to support dissolved concentrations. This study employs two new assessment tools to quantify the bioavailability of sediment-bound contaminants to evaluate the efficacy of in situ AC treatments. Our broad goal is to assist in the development of the next generation of contaminated sediment management tools.

Prepared in cooperation with the University of Maryland, University of Maryland Baltimore County, and Goucher College. The original document contains color images.