A CASE STUDY FOR SEDIMENT AND CONTAMINANT STORAGE IN FLOOD PLAIN TIDAL PONDS: SELDEN COVE, CONNECTICUT RIVER

The Connecticut River Estuary has inherited a legacy of contamination since the onset of industrialization. Tidal ponds and coves along the river provide ample storage space for the deposition of fine-grained sediment and likely serve as a primary depocenter for contaminants introduced to the river over the last few centuries. Here we present sedimentological and geophysical data from Selden Cove, a fresh water tidal pond located along the floodplain of the Connecticut River, in order to assess the inventories of sediment and heavy metal contaminants. Using ground-penetrating radar surveys, we are able to determine patterns and spatial distributions of depositional units within the sub-bottom. Cesium-137 is used to evaluate decadal rates of deposition as well as define temporal stratigraphic horizons. Mercury analyses indicate sediments deposited since industrialization and provide an additional chronological constraint for evaluating centennial rates of deposition. Using these tools, we are able to determine the total volume of contaminated sediment stored within the cove as well as an inventory for the total amount of Mercury which has accumulated in the pond since the mid-1800s. These inventories are then compared to previous published results for neighboring marsh locations in order to assess the relative role floodplain tidal ponds play in the storage of contaminated sediment.