DISTRIBUTION OF TOXIC METALS IN SURFACE SEDIMENTS OF THE NORTH RIVER ESTUARY, SALEM, MA

The North River is located in Salem, Massachusetts, and flows through the cities of Peabody and Salem. The North River estuary adjoins the Danvers River estuary to form Beverly Harbor of Salem Sound. The North River is part of an urban watershed and was heavily industrialized throughout the late 19^th and 20^th centuries. Previous studies indicate that sediment within the river and estuary contains large concentrations of toxic metals. In an attempt to identify any trends regarding the source of the toxic metals in the estuary a contour map detailing the concentrations of toxic metals in the upper 7cm of sediment was composed using ArcMap software. Surface grab samples were dried, homogenized and analyzed using an X-ray fluorescent (XRF) spectrometer. Concentrations of As, Cd, Cr, Cu, Pb, and Zn in the samples were compared to revised ERL and ERM sediment quality guidelines. Mean concentrations of Cr, Cu, Zn, Pb, and Cd exceed ERM standards throughout the estuary. The overall trend indicates that concentrations decrease away from the mouth of the river into the estuary. However, contour maps reveal multiple areas of anomalously high concentrations of toxic metals as well. Historical georeferencing shows elevated industrial activity, mainly of the tanning industry along the river. The chrome tanning method used in the tanneries produces high levels of chromium waste which was often dumped directly into the river. Differences in the pattern of Ni concentrations suggest multiple sources of toxic metals. 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 study site, and recent construction of a public park which was terminated upon discovery of toxic concentrations of lead, mercury, copper, and chromium in soil as deep as 1m. Redistribution of the metals may have occurred as a result of revitalization attempts in the vacant industrial complexes along the river. Redistribution of toxic metals suggests the necessity of erosion control as a means to sequester contaminants and prevent further spread into estuaries, harbor, and Salem Sound.