DISTRIBUTION OF TOXIC METALS IN SURFACE SEDIMENT OF THE NORTH RIVER AND FOREST RIVER ESTUARIES, SALEM, MA

The North River and Forest River in Salem, MA, form the primary drainage systems into Salem Sound. Previous studies of both field areas indicate that surface sediment contains high concentrations of toxic metals. In an attempt to identify any trends regarding the distribution of the toxic metals, contour maps of toxic metals in the upper 7cm of sediment were produced using ArcMap software. In both sites, the overall trend indicates that concentrations decrease away from the mouth of the river into the estuary. Contour maps also reveal multiple areas of anomalously high concentrations of toxic metals. Anomalous distributions of toxic metal concentrations, at both sites suggest that the metals are derived from different sources or are mobilized differently. Concentrations of As, Cd, Cr, Cu, Pb, and Zn in the samples were compared to revised ERL and ERM sediment quality guidelines. Concentrations of Cr, Cu, Zn, Pb, and Cd exceed ERM standards consistently throughout the North River estuary whereas concentrations exceeding ERM standards are not as consistent in the Forest River estuary. Sediment Quality Guideline Quotients were calculated and contoured to assess the overall toxicity of both study sites.

Although both sites show elevated concentrations of toxic metals significant differences in concentrations between the sites likely reflect differences in land use history. Higher concentrations in the North River show a correlation between density of industrial activity and toxic metal concentrations. Historical georeferencing of the watersheds show elevated industrial activity along the North River during the 19^th and 20^th centuries, whereas much of the land surrounding the Forest River estuary is conservation land with a residential land use history. The Direct sources of toxic metals specific to the North River estuary that likely contribute to the higher concentrations of toxic metals include chromium waste from tanneries, a junkyard located on the west bank of the study site, and remobilization during revitalization of industrial complexes. Though the sites have different land use histories regional sources such as emissions from a coal fired power plant and storm water runoff.