Historical contamination of PAHs, PCBs, DDTs, and heavy metals in Mississippi River Delta, Galveston Bay and Tampa Bay sediment cores

Profiles of trace contaminant concentrations in sediment columns can be a n atural archive from which pollutant inputs into coastal areas can be recons tructed. Reconstruction of historical inputs of anthropogenic chemicals is important for improving management strategies and evaluating the success of recent pollution controls measures. Here we report a reconstruction of his torical contamination into three coastal sites along the US Gulf Coast: Mis sissippi River Delta, Galveston Bay and Tamps Bay. Within the watersheds of these areas are extensive agricultural lands as well as more than 50% of t he chemical and refinery capacity of the USA. Despite this pollution potent ial, relatively low concentrations of trace metals and trace organic contam inants were found in one core from each of the three sites. Concentrations and fluxes of most trace metals found in surface sediments at these three s ites, when normalized to Al, are typical for uncontaminated Gulf Coast sedi ments. Hydrophobic trace organic contaminants that are anthropogenic (polyc yclic aromatic hydrocarbons, DDTs, and polychlorinated biphenyls) are found in sediments from all locations. The presence in surface sediments from th e Mississippi River Delta of low level trace contaminants such as DDTs, whi ch were banned in the early 1970's, indicate that they are still washed out from cultivated soils. It appears that the DDTs profile in that sediment c ore was produced by a combination of erosion processes of riverine and othe r sedimentary deposits during floods. Most of the pollutant profiles indica te that present-day conditions have improved from the more contaminated con ditions in the 1950-1970's, before the advent of the Clean Water Act. (C) 2 001 Elsevier Science Ltd. All rights reserved.