Metal accumulation in Baltimore Harbor: current and past inputs

The analysis of sediment cores taken from 3 regions of Baltimore Harbor, Maryland, USA, provide insight into contamination in the 20th century, as well as in earlier times. Overall, while there appears to have been a decrease in concentration for most metals over the last 20 a, concentrations of some metals in surface sediment layers, such as Cr and Pb, are still elevated. The deeper sediments, which reflect times before 1900, often contained higher concentrations of metals and reflect a large historical contamination of this region due to industrial inputs and other activities. Mining and smelting impacts are apparent, being reflected by elevated concentrations of Zn, Pb, Cu, Cd and As, and such impacts are seen in the Middle Branch of the estuary during the 1700s and elsewhere in the 1800s as Cu and other ore processing, and steel manufacture, increased. Comparison of the profiles for the metals, and accumulation rates, suggest that the sources of most metals are different. For each site, the particular metal signature recorded in the sediment can be explained in terms of the known activities in the watershed. At one site, sediments from the period prior to the European settlement were analyzed and these show low concentrations reflective of the situation before industrialization and urbanization of the watershed. (C) 2004 Elsevier Ltd. All rights reserved.