Sedimentary coprostanol and hydrocarbon distribution adjacent to a sewage outfall

The concentrations of coprostanol and hydrocarbons were measured in the effluent from the Chesapeake-Elizabeth sewage treatment plant (STP) and surface sediments from the area surrounding the effluent discharge site. Most of the coprostanol (> 84%) and hydrocarbons (> 91%) were associated with particulates in the effluent. The area was found to be dynamic where changes in the percentage and distribution of fine grained sediments occur over periods of months and the movement of these sediments is an important determinant of the distribution of sewage derived contaminants. The Chesapeake-Elizabeth STP was found to be responsible for only 7% of the hydrocarbon contamination of the sediments in the study area. The sediment hydrocarbon distribution also indicates that the Bay Bridge tunnel may be a unique source of hydrocarbons to the lower Chesapeake Bay. This study shows the usefulness of coprostanol in providing a better understanding of the fate and importance of sewage derived contaminants in areas around sewage outfalls.