USGS Studies in Long Island Sound:
Geology, Contaminants, and Environmental Issues

Sediment cores and surficial grab samples (click here for a map showing locations) were collected in Long Island Sound for geochemical analysis (1) in North-South transects within Long Island Sound, (2) throughout the Sound for verification of sidescan sonar interpretations, (3) in study areas targeting critical habitats, and (4) in areas with good preservation of historical signals. Sampling cruises encompassed the period from 1993 to 2001.

Sediment cores were collected in 1996 using the U.S. Geological Survey's hydrostatically-damped gravity corer (HDGC), and in 2001 with a free-falling gravity corer. The HDGC collected 11-cm diameter cores of 15 to 70 cm in length in clear, polycarbonate tubing. There was minimal disturbance of the sediment surface and a video camera was mounted on the frame of the corer to record the entry of the corer into the sediment. On deck, the cores were capped, described, and stored vertically for later sectioning and analysis. Cores collected in 2001 were acquired with a free-falling gravity core that sampled up to 245 cm of sediment in a PVC barrel. Cores were x-rayed, extruded in the laboratory, subsampled at selected intervals, and aliquots separated for analysis.

Surface sediment samples were collected with a teflon-coated Van-Veen grab sampler with attached bottom video. On deck, the sediment-grab was photographed, overlying water removed, and the upper 2-cm of sediment collected with a Teflon-coated flat-bottom scoop. Each sediment sample was placed in a pre-cleaned plastic container and aliquots separated for geochemical and other analysis.

Physical descriptions, X-radiographs (relative density) and Multi-Sensor Core Logger Data (magnetic susceptibility, bulk density, and P-wave travel time) were collected on whole sediment cores. Sectioned core samples and surface grab samples were analyzed for physical properties (water content, sediment grain size) and for chemical composition after total digestion. Measured parameters included both contaminants and the major and trace elements that characterize natural sediments (see table). Selected samples were also analyzed for radiochemistry (210Pb and 137Cs), pollen, foraminifera, toxicity, organic contaminants, and magnetic properties. Data and samples are archived at the USGS Woods Hole Field Center and will be made available through this website.