Remobilization of Metals from Polluted Marine Sediments

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Abstract
The transition metals Cu, Pb, Fe, Mn, and Cd were examined to estimate short- and long-term release rates from highly contaminated sediments and to compare this release with present metal flux into an ecosystem. The concentration of Cu and Pb increased in the water column over contaminated marine sediments when these sediments were isolated from metal and organic carbon sources and held in large (13 m3) marine microcosms. During the summer and early fall, Cu concentrations increased by a factor of 3 relative to the concentration in microcosms containing slightly polluted and uncontaminated sediments. Mass balance calculations indicate that 840 and 21 μmol∙m−2∙yr−1 Cu and Pb, respectively, were mobilized and exported from the microcosms with highly contaminated sediments, while less-contaminated sediments lost 120 μmol Cu∙m−2∙yr−1. Iron and Mn were not exported from the microcosms. In the absence of high sedimentation rates and high bioturbation rates, the diffusive loss of Cu and Pb may be sufficient to return the upper 1 cm of sediment to background levels in 44 and 400 yr, respectively. This remobilization is a small percentage of current inputs to Narragansett Bay.

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