M6 PM Fate and Transport of Pollutants from Dredging and Placement
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 324-326

(GAR-1117-807761) Colloid- and DOC-facilitated Leaching of Metals from Contaminated Estuarine Sediments in Freshwater Upland Environments.

Gardner, K¹, Tsiatsios, C¹, ¹ University of New Hampshire, Durham, NH, USA

ABSTRACT- This research focused on the leaching characteristics of metals from NY/NJ Harbor and New Bedford Harbor sediments. Contaminant release estimates and mass flux rates were evaluated using batch tests and column leaching tests. Column leaching tests were conducted to quantify the significance of colloid-facilitated transport of metals from estuarine sediments being managed in freshwater environments. Colloidal release occurred after the high ionic strength pore water was washed-out by low ionic strength eluent, which mimicked rainfall infiltration into a CDF or similar fill application. Leachate dissolved organic carbon (DOC) and metal elution trends were similar. It was found that metals associated with DOC and not with larger turbidity-causing particulates (>0.02 micrometer). Visual MINTEQ modeling indicated a strong metal-DOC relationship with the complexed species accounting for an average percent of total dissolved concentration of 89.8% and 99.5% at 5.5 and 30 pore volumes, respectively. This suggests the metals were complexed with DOC, which facilitated the transport of contaminants from the estuarine sediments. The results from the LS ratio dependent batch tests and column leaching tests were compared to determine if the batch tests adequately describe the leaching behavior of metals from sediment over time. In general, there was good agreement (less than one order of magnitude) at low LS ratios but the accuracy of the predicted metal leachate concentrations decreased at high LS ratios (>5mL/g). It seems that the column tests do capture some phenomena not observed in batch leaching tests, particularly the release of DOC and associated metals.

Key words: colloid, DOC, CDF, leaching