Geochemical study of sediment contamination in New Bedford Harbor, Massachusetts

Chemical analyses of sediment samples collected along a transect in New Bedford Harbor revealed a gradient of increasing concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo- p-dioxins (PCDDS), polychlorinated dibenzofurans (PCDFs), polycyclic aromatic hydrocarbons (PAHs) and several trace metals from the southern to the northern areas of the estuary. Although the concentrations of contaminants generally increased with distance north in the estuary for all classes of compounds, differences were observed between the trends for many of the compounds. These differences are probably due to both the sources and differential environmental behaviors of the compounds in the estuary. The primary sources of PCBs, PCDFs and trace metals appear to be industrial discharges either directly into the estuary or through combined sewer overflows. Additional inputs of PCDFs may have also impacted the lower portions of the harbor. These inputs may be from the combustion of sewage sludge containing high concentrations of PCBs at the New Bedford Harbor Municipal Wastewater Treatment Plant. The major inputs of PAHs and PCDDs are probably from urban runoff entering the harbor through combined sewer overflows and storm drains.