BENEATH COASTAL WATERS: AN OVERVIEW OF CONTAMINATED SEDIMENTS IN THE NORTHEAST

Coastal environments represent the interface between aquatic and terrestrial systems and are often affected by chemical contamination, leading to a degradation of environmental quality and health of coastal systems. Regional studies of coastal sediments in the Northeast conducted by the U.S. Geological Survey show that trace metal contamination from land-based activities has occurred near the major urban centers. Enrichment of metals, such as Cu, Pb, Zn, Hg, and Ag, of 2-5 times naturally occurring background-levels occurs in sediments of Boston Harbor, Long Island Sound, Gulf of Maine coastal regions, and the New York Bight. Contaminant accumulations are strongly influenced by the sediment lithology and sediment transport properties in local areas. In most of the cores examined, increases in metal contaminants over the past 200 years correspond with local population growth and are highly correlated with the abundance of a bacterial sewage indicator,Clostridium perfringens. The onset of metal contamination in the Northeast sediment record occurs in the mid-1800s, with inputs increasing in the mid-1900s and decreasing (20-50%) from the 1970’s to the present. Increases in organic carbon and nitrogen in the sediment also reflect population growth and changes in waste-treatment practices over this time. Rates at which coastal sediments concentrate contaminants from riverine, atmospheric, and direct input sources differ from rates of sediment burial and mixing, so predictive models are required to estimate the long-term fate of the pollutants currently in the coastal sediments and their impact on the ecosystem. Both the spatial and the temporal distribution of contaminants in sediments in the Northeast indicate that humans have profoundly changed the environmental character of our coastal system.