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W2 AM Chesapeake Bay Restoration (Part 1)
(BAK-1118-586716) Challenges of assessing and managing persistent bioaccumulative toxins in the Chesapeake Bay.
Baker, J1, 1 University of Maryland, Solomons, MD, USA
ABSTRACT- During the past decade, we have conducted field assessments to determine the concentrations, inventories, and sources of persistent bioaccumulative toxins (PBTs) in the Cheasapeake Bay estuary. Increasingly stringent risk-based thresholds have resulted from improved ecological and human health risk analyses that use sub-lethal endpoints. In the Chesapeake Bay, levels of polychlorinated biphenyls (PCBs) in estuarine fish commonly exceed the most cautious risk-based concentrations, resulting in fish consumption advisories. One goal of our studies is to estimate the magnitudes and relative importance of PCB sources to the Chesapeake Bay. Using the mass balance paradigm, the relative magnitude of storm water, riverine discharge, atmospheric deposition, and point sources are determined. For example, long-term monitoring of the Susquehanna River tributary, which provides 60% of the freshwater flow to the Chesapeake Bay, determined that 76 kg of t-PCB were delivered from the Susquehanna watershed each year. The source of these PCBs to this largely agricultural and forested watershed are unknown. We have developed a spatially-explicit, time-variable model of PBT transport in the estuary to explore the exchange of chemicals between the sediment-water and air-water interfaces, with emphasis on quantifying release of PCBs from contaminated sediments. In addition to 'legacy' PBTs such as PCBs, our recent assessments include the first study of the sources and cycling of brominated flame retardants in the estuary. Current levels of these compounds are quite low in the Chesapeake relative to those documented to cause affects, but their nearly exponential rise in production and use will require continued environmental assessments.
Key words: Chesapeake Bay, PCBs, bioaccumulative, PBDEs
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