The Geochemistry Of Coprostanol In Waters, Surface Sediments And Sediment Cores From Narragansett Bay

A geochemical study of coprostanol (Sa-Cholestan-36-01) in Narragansett Bay, Rhode Island was undertaken to examine the fate and transport of a compound of moderate polarity and reactivity in an estuarine environment, and because of interest in this fecal sterol. as a sewage tracer. Four times during 1 9 8 5 1 9 8 6 discharges from five river mouths and eleven point sources were sampled, as well as four bay stations at three water depths. In addition, surface sediments from twenty-six stations throughout the bay were collected. In conjunction with this study, samples were also analyzed for a suite of organic compounds, including petroleum hydrocarbons, PCBs, PAHs, substituted bensotriazoles and phthalates. Analysis was by fused silica capillary column gas chromatography, using flame ionization and electron capture detectors, as well as verification of selected samples by gas chromatograph/mass spectrometry. Coprostanol concentrations in thewaters (0 .02 0.22 ug/l),andsurface sediments (0 .22 33 ug/g) from the bay were as high or higher than any values reported in the literature, indicating that the bay is severely impacted by sewage. Effluent concentrations of coprostanol from secondary sewage treatment plants were consistently lower than primary treatment plant effluents, demonstrating the usefulness of coprostanol as a indicator of treatment plant efficiency. The survey of point sources and rivers revealed that 50% of the total particulate coprostanol was discharged into the Providence River, primarily due to the discharge from the sewage treatment facility at Fields Point, which is the largest plant in the state. The Newport Sewage treatment Facility, a primary treatment plant in the lower bay, was the largest single source of particulate coprostanol to the entire bay. The distribution of coprostanol in waters and surface sediments, showed a gradient of decreasing concentration downbay, suggesting that the Providence River concentrations of substituted bensotriazoles and the PCB congener 209 in surface sediments indicated the importance of riverine input as a source of anthropogenic pollutants, including coprostanol, which originates from sewage treatment plants discharging into the rivers.