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Harvard School of Public Health

Superfund Research Program

Improving Ecological Risk Assessment: Development and Application of Methods to Determine the Bioavailability of Contaminants in Aquatic Sediments - New Bedford SF Site

Project Leader: James P. Shine
Grant Number: P42ES005947
Funding Period: 1995 - 2006

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Project Summary (2000-2006)

The goal of this project is to develop and field test sampling devices that determine the free activity (as opposed to the total concentration) of metal and organic contaminants in aquatic sediments. The total concentration of contaminants in an environmental matrix is not necessarily predictive of the potential for adverse ecological or public health effects. Contaminants introduced to the environment can undergo a variety of reactions that reduce their activity and thus their bioavailability to target organisms. These reactions include sorption onto or into particles, complexation with detrital organic matter, and precipitation as insoluble complexes. The sampling devices being developed by the project investigators are designed to determine the fraction of contaminants in a sample available for partitioning into target receptors. The basic premise of the samplers is to introduce a solid or liquid substrate with a known thermodynamic affinity for a contaminant of interest. The extent of contaminant partitioning to the substrate can be used to determine the contaminant's activity in the original sample. The primary hypothesis under investigation is that the presence of soot phase carbon (in addition to total organic carbon) from hydrocarbon combustion will alter the partitioning of PAHs such that a pyrogenic mixture of PAH's from combustion sources will be less bioavailable than a similar concentration of a petrogenic mixture of PAHs arising from oil spills. For metal contaminants, the researchers are testing the hypothesis that the free ion concentration of metals in sediment pore waters is a function of both sulfide concentration and total organic carbon, and that approaches can be developed to predict free metal ion concentrations from both the sulfide and total organic carbon concentrations.

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