DISTRIBUTION OF TOXIC METALS IN SURFACE SEDIMENT OF THE NORTH RIVER AND FOREST RIVER ESTUARIES, SALEM, MA: EXPLORATION OF POSSIBLE SOURCES AND INFLUENCES ON DISTRIBUTION

The North River and Forest River are part of an urban watershed, the rivers flow through the city of Salem, Massachusetts, and ultimately into Salem Sound. Previous studies of both field areas indicate that sediment within the estuaries contain large concentrations of toxic metals. In an attempt to identify any trends regarding sources and distribution, contour maps detailing the concentrations of toxic metals in the surface sediment were composed using ArcMap software. Samples were dried, homogenized, and analyzed using an X-ray fluorescent (XRF) spectrometer. Concentrations of Ag, Cd, Cr, Cu, Pb, and Zn in the samples were compared to revised ERL and ERM sediment quality guidelines. Concentrations of Ag, Cd, Cr, Cu, Ni, and Pb exceed ERM standards throughout both estuaries. In addition, mean ERM quotients were contoured to assess the overall toxicity of sediment. The contour maps also reveal multiple areas of anomalously high concentrations of toxic metals. Observed plumes of high concentrations radiating from storm water out fall pipes suggest that the effects of storm water runoff greatly impact toxic metal concentrations in the sediment of both field areas. Differences in the distribution of toxic metal concentrations in both field areas suggest multiple sources. Historical georeferencing shows elevated industrial activity, mainly of the tanning industry 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 and has a residential land use history with the exception of a vacant lead mill and an electric light factory near the mouth of the estuary. Correlations between toxic metals used in hide tanning suggest that the industrial activity continues to affect the area. Comparison of land use history suggests a higher impact of industrial activity in the North River field area. Other probable direct sources of toxic metals in the North River estuary include emissions from a coal fired power plant, a junkyard located on the west bank of the field area, and railroad tracks along the east bank of the field area. Increased erosion and apparent redistribution of toxic metals in the Forest River estuary suggests the necessity of erosion control as a means to sequester contaminants and prevent further spread into estuaries, harbor, and Salem Sound.