Trace metal leachability of land-disposed dredged sediments

The potential risk of surface and ground water contamination by trace metal s leached from contaminated land-disposed dredged sediment is a major envir onmental concern. The objective of this study was to evaluate trace metal l eachability, leachate quality, and environmental effects of land-disposed d redged sediments (LDDS), In addition to chemical characterization and deter mination of potential and actual leachability, dredged sediments were also subjected to solid phase fractionation using a sequential extraction proced ure, Potential leachability, defined as the maximum metal pool that may bec ome available fur leaching at a constant pH 4, decreased in the following o rder: Zn similar to Cd > Mn > Ni > Co > Cu similar to As > Pb > Cr, Potenti al metal leachability was controlled mainly by solid phase distribution of metals in sediments. The acid-extractable fraction of most metals correlate d well with the potentially leachable metals extracted with a solution of p H 4 (r(2) > 0.67), except for Pb. The kinetics of metal release were determ ined using the cascade leaching test (CLT) with water at pH ii, Except for Ni and Zn in the first traction. metal concentrations in all consecutive le aching fractions remained below the maximum permissible level in water for human consumption. Actual metal leachability expressed as a percentage of p otential leachability varied widely among trace metals and decreased in the order: As > Cu > Cr > Ni > Zn > Cd > Co > Pb, Our results indicate low ris k of surface and ground water contamination resulting from land disposal of dredged sediments.