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M6 PM Fate and Transport of Pollutants from Dredging and Placement
(GAR-1117-807215) Assessment of Leaching Potential of Metals from Contaminated Sediments Placed in Upland Environments.
Gardner, K1, Tsiatsios, C1, Melton, J1, 1 University of New Hampshire, Durham, NH, USA
ABSTRACT- This research focused on the leaching characteristics of metals from NY/NJ Harbor sediments. Sediments were evaluated as fill materials in an as-is state and with the addition of 7% dry Portland cement to 93% wet dredged material which created a suitable controlled low strength material (also called flowable-fill) product. Contaminant release estimates and mass flux rates were evaluated using pH-dependent leaching, liquid-to-solid ratio dependent leaching and column leaching. A simple percolation model and the EPA Industrial Waste Management Evaluation Model (IWEM) were used to evaluate the release of metals into the groundwater at a theoretical site using parameters from the Bark Camp Mine site in Pennsylvania. Results showed that the stabilization of contaminated sediments with Portland cement reduces the leachability of metals at pH values greater than 9, but does not affect release at pH values less than 9 for As, Cd, Cr, Cu, Ni and Pb. The flowable fill material has a natural pH of 11.2-12.2 with a high buffering capacity. Under acid rain percolation conditions, the flowable fill would be expected to remain above a pH 9 for approximately 10,000 years. The estimated concentration of metals leached during a 100-year time interval for the as-is sediment and flowable fill material averaged 23.6% and 4.4% of the total metals, respectively. The flux and IWEM results showed a decrease in the mass rate of transfer and groundwater metal concentrations after stabilization in the flowable fill matrix for As, Cd, Cr, Ni, Pb and Zn, respectively. Cu has a greater release after stabilization due to complexation with dissolved organic carbon released at the high pH of the flowable fill matrix. IWEM was found to be a useful modeling context to consider the environmental impact of fills using sediments.
Key words: stabilized sediment, beneficial use, leaching
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