Trace metals and radionuclides reveal sediment sources and accumulation rates in Jordan Cove, Connecticut

Many small estuaries are influenced by flow restrictions resulting from tra nsportation rights-of-way and other causes. The biogeochemical functioning and history of such systems can be evaluated through study of their sedimen ts. Ten long and six short cores were collected from the length of Jordan C ove, Connecticut, a Long Island Sound subestuary, and analyzed for stratigr aphy, radionuclides (C-14, Pb-210, Ra-226, Cs-137, and Co-60), and metals ( Ag, Cd, Cu, ph, Zn, Fe, and Al). For at least 3,800 yr, rising sea level ha s gradually inundated Jordan Cove, filling it with mud similar to that curr ently being deposited there. Long-term sediment accumulation in the cove av eraged close to 0.1 cm yr(-1) over the last three millennia. Recent sedimen t accumulation rates decrease inland from 0.84 cm yr(-1) to 0.40 cm yr(-1), and are slightly faster than relative sea-level rise at this site (0.3 cm yr(-1)). Similarity of depth distributions of trace metals was used to conf irm relative sediment accumulation rates. Co-60 and Ag are derived from sou rces outside the cove and its watershed, presumably the Millstone nuclear p ower plant and regional contaminated sediments, respectively. The combined data suggest that Long Island Sound is an important source of sediment to t he cove; a minor part of total sediment is supplied from the local watershe d. Trace metal levels are strongly correlated with Fe but not with either o rganic matter or Al. Sediment quality has declined in the cove over the pas t 60 yr, but only slightly. Cu, Pb, and Zn data correlate strongly with Fe but not with either organic matter or aluminum. Ratios of Ag to Fe and to t race metals suggest that Ag in the cove is derived almost entirely from Lon g Island Sound. This result supports the notion that Fe-normalized Ag can s erve as a better tracer of some kinds of contamination than more common and abundant metals, like Cu, Pb, and Zn.