Potential contaminants at a dredged spoil placement site,Charles City County,Virginia, as revealed by sequential extraction |
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Authors: | Email author" target="_blank">Jianwu?TangEmail author G?Richard?Whittecar Karen?H?Johannesson W?Lee?Daniels |
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Institution: | (1) Department of Ocean, Earth & Atmospheric Sciences, Old Dominion University, Norfolk, Virginia, 23529-0267;(2) Department of Geology, The University of Texas at Arlington, Arlington, Texas, 76019-0049;(3) Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, 244 Smyth Hall, Blacksburg, Virginia, 24061-0404 |
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Abstract: | Backfills of dredged sediments onto a former sand and gravel mine site in Charles City County, VA may have the potential to
contaminate local groundwater. To evaluate the mobility of trace elements and to identify the potential contaminants from
the dredged sediments, a sequential extraction scheme was used to partition trace elements associated with the sediments from
the local aquifer and the dredged sediments into five fractions: exchangeable, acidic, reducible, oxidizable, and residual
phases. Sequential extractions indicate that, for most of the trace elements examined, the residual phases account for the
largest proportion of the total concentrations, and their total extractable fractions are mainly from reducible and oxidizable
phases. Only Cd, Pb, and Zn have an appreciable extractable proportion from the acidic phase in the filled dredged sediments.
Our groundwater monitoring data suggest that the dredged sediments are mainly subject to a decrease in pH and a series of oxidation reactions, when exposed to the atmosphere. Because the trace elements released by carbonate dissolution
and the oxidation (e.g., organic matter degradation, iron sulfide and, ammonia oxidation) are subsequently immobilized by
sorption to iron, manganese, and aluminum oxides, no potential contaminants to local groundwater are expected by addition
of the dredged sediments to this site. |
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