Abstract
DuPont Edgemoor waste derived from titanium dioxide production is a highly acidic solution of ferric chloride containing relatively high levels of several trace metals including Cr, V, Pb, Ni, Cu, and Cd. Approximately 3 × 105 t∙yr−1 are dumped at Deepwater Dumpsite 106, ~160 km southeast of Ambrose Light, New York. Chemical dispersion studies at the dumpsite indicate that ferric oxide precipitates in the waste plume and that other trace metals may become associated with this particulate phase. Ingestion of this particulate phase by copepods is a significant route of uptake for the waste-derived metals in the laboratory. Accumulation of the various metals by exposed copepods ranged from 10.8% above control values for Fe to 54.7% for Cu. The ratios of the various trace metals relative to Fe were only slightly enhanced in exposed copepods in comparison with control copepods but 1 to 2 orders of magnitude higher than the metal ratios of a 105 waste dilution. Enhancement of metal concentrations in fecal pellets produced by exposed copepods ranged from 25.0% above control values for Fe to 60.3% for Cu. Metal deposition through fecal pellet production appears to be an effective means of depurating Fe, Pb, Ni, and Cu by copepods exposed to Edgemoor waste but not for Cd, which could not be detected in fecal pellets. The greater density of fecal pellets compared with the ferric oxide particles could result in a more rapid sinking rate of waste-derived metals to the deep ocean. The flux of waste-derived metals through Zooplankton biomass and the contribution of Zooplankton in the biogeochemical cycling of metals at Deepwater Dumpsite 106 suggests that biological processes may be as important as advective processes in determining the fate of waste-derived metals.
Published Version
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