DETAILED MAPPING OF TOXIC TRACE METAL CONTAMINATED SEDIMENTS USING THE GEOMORPHOLOGICAL-GEOCHEMICAL APPROACH, TROUT BROOK, WEST HARTFORD, CONNECTICUT

Sediment sampling for toxic trace elements that adsorb to the fine fraction of bedload sediments (<63 μm) requires a detailed understanding of geomorphological stream bed features such as bar/channel deposits, vegetated islands, natural dams, and point bars. In addition, the chemical parameters of the river need to be well-defined in order to predict where toxic metals are accumulating (sediment vs. solution). To quantify changes in trace metal concentrations within bed-load sediments a series of high density sampling arrays were sampled around an active point source discharge of a closed landfill within the Trout Brook, a channelized tributary of the Park River, in Hartford, CT. Waters of the Trout Brook are well oxygenated and have pH values of 7-9 and therefore little to no trace metals are found in solution during both base and storm flow.

The sediment sampling array was sampled before and after two storm water events in the summer of 2010 to observe changes in bedload concentrations for Pb, Cu, Cd, and Zn. While high concentrations of Pb (exceeding 130 ppm) were observed to be ubiquitous throughout the stream channel , Cu, Cd, and Zn were shown to be in toxic concentrations just downstream from the landfill outfall. However, local stream channel sediment traps within the sample array also were shown to affect the concentrations of metals and require a more careful analysis. Contoured concentration data were plotted in ArcGIS (v.10) using spline interpolation methods. All sediment was processed using a weak acid digestion method and analyzed using ICP-OES.