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Efficacy of sediment remediation efforts on PAH contaminant flux via porewater advection at the sediment-surface water interface
Krask, Julie L. Unger, Michael A. Vadas, George G. Cochran, Michele A. Beck, Aaron J.
Krask, Julie L.
Unger, Michael A.
Vadas, George G.
Cochran, Michele A.
Beck, Aaron J.
Abstract
Groundwater advection at the sediment-surface water interface is an important biogeochemical mechanism controlling the transport and bioavailability of contaminants in estuaries. At sites along the Elizabeth River (VA, USA) where the subterranean environment is heavily contaminated with polycyclic aromatic hydrocarbon (PAH)-rich dense non-aqueous phase liquid (DNAPL), consideration of groundwater-surface water dynamics and associated chemical exchange is critical for effective remediation. Preliminary data suggest that porewater advection in permeable sediments at this location is controlled by a host of physical forcing mechanisms that correspond with total flow estimates of up to 15,000 centimeters/year. Here, the efficacy of sediment remediation strategies, including dredging and capping DNAPL-laden sediments as well as implantation of a groundwater-blocking sheet pile wall, was evaluated with respect to groundwater and contaminant fluxes using naturally-occurring radionuclide tracers and a PAH antibody-based biosensor. Comparison of these data with results from similar analyses conducted at neighboring sites targeted for future remediation was provided to environmental managers to help guide future remediation efforts. Preliminary results revealed total PAH concentrations of up to >400 μg/L in groundwater at subsurface depths up to 80 centimeters in the unremediated zone and corresponding salinity measurements of 5 –8 ppt, compared with a surface water salinity of 18 ppt. Groundwater samples from sediment depths reaching 120 centimeters at the recently remediated location had comparably low salinities and elevated PAH concentrations. These data provided strong evidence for the role of fresh groundwater contaminated with DNAPL as a major mode of PAH transport and suggest the need to devise additional, innovative strategies to mitigate porewater-associated contaminant flux.
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2015-10-09
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Posters, Poster, VIMS 75th Anniversary, Institute History, Alumni, Groundwater, Sediments, Environmental Remediation
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Virginia Institute of Marine Science