The effects of pH, redox, and salinity on metal release from a contaminated sediment

A laboratory study was conducted with a brackish marsh sediment contaminated by several trace and toxic metals to determine the effect of a range of pH, redox potential, and salinity conditions on the release of metals to the soluble phase. The purpose of the study was to provide information on factors affecting the mobilization/immobilization of metal contaminants under conditions of various possible remediation alternatives. Substantial amounts of Cd and Zn were released under moderately acid, oxidizing conditions. Under the present slightly basic, strongly anaerobic environment of the marsh sediment, the metals are being effectively immobilized compared to the release that would occur for some of the metals if the sediments were excavated and placed under upland conditions where they would eventually become oxidized and strongly acidic.