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DISSOLVED-COLLOIDAL PARTITIONING OF MOBILIZED METALS DURING RESUSPENSION OF MARINE SEDIMENTS
Citation:
Cantwell, M AND R M. Burgess. DISSOLVED-COLLOIDAL PARTITIONING OF MOBILIZED METALS DURING RESUSPENSION OF MARINE SEDIMENTS. Presented at Society of Environmental Toxicology and Chemistry, Baltimore, MD, November 11-15, 2001.
Description:
Sediments in many urban estuaries are contaminated by potentially toxic heavy metals. Over time, many of these metals accumulate in the sediment due to physico-chemical processes which remove them from the water column. Marine sediments are regularly subjected to physical processes which resuspends them into the water column, potentially releasing sequestered metals and increasing their bioavailability. Natural processes including tides and storms along with anthropogenically induced perturbations such as ship traffic and dredging are all events which may entrain sediments in the water column. In order to better predict how metals partition during resuspension events, it is essential to understand the factors influencing their distribution. A particle entrainment simulator (PES) was used to resuspend two anoxic metal contaminated sediments collected from Narragansett Bay, (RI). Sediments were resuspended for 12 hours at two energy levels and water column samples were taken at specified intervals. Following collection, dissolved and colloidal metals were isolated using stirred cell ultrafiltration. Partitioning coefficients (Kps) were calculated for potentially toxic metals (Cu, Ni, Zn) as well as iron and manganese. Results indicate that the level of resuspension energy imparted is not an important factor influencing metal partitioning between the dissolved and colloidal phases. The sediment's physical and chemical composition played the major role, controlling the amount of sediment resuspended, as well as water column conditions. Calculated partitioning coefficients for most metals remained unchanged over the twelve hour test period, with the exception of iron, which decreased over time. These data indicate that equilibrium of Cu, Ni and Zn between dissolved and colloidal phases is established rapidly following resuspension. This information will expand our understanding of metals bioavailability and improve predictive capability beyond the existing EqP model.