Objective

For contaminated sediment sites, risk reduction is achieved primarily by reducing chemical availability in the biologically active zone of sediment. Successful achievement of this target goal may be limited, however, by the incomplete understanding of chemical bioavailability. Questions regarding chemical bioavailability are of concern for mercury (Hg)-impacted sites because the production rate of methylmercury (MeHg) may be correlated with sediment inorganic Hg concentration, making dissolved Hg and MeHg bioavailable to lower trophic level organisms. Development of improved methods for understanding the relationship between chemical concentration and chemical bioavailability will enable more accurate site-specific assessment of risk, as well as improved understanding of Hg and MeHg exchange between sediment and porewater.

The objective of this project is to develop engineering tools (hydrogels) for more cost-effective assessment of Hg and MeHg bioavailability in sediment. Laboratory syntheses, experimental manipulations, numerical modeling, and laboratory and field deployments will be used to examine the nexus between chemical lability, as defined by the kinetics of Hg and MeHg uptake by the hydrogels, and chemical bioavailability, as defined by the extent to which Hg and MeHg are available to benthic fauna. Specific objectives of this project are to examine the extent to which hydrogel data are representative of tissue Hg and MeHg concentrations for a range of benthic feeding guilds, develop a methodology to screen the effectiveness of reactive amendments as a remedial strategy for Hg-impacted sites, and assess the effectiveness of hydrogels as a field-based bioavailability screening tool.