SEDIMENTARY COPROSTANOL AS AN INDEX OF SEWAGE ADDITION IN SANTA-MONICA BASIN, SOUTHERN-CALIFORNIA

Sediment cores from Santa Monica Basin and effluent from two major municipal wastewater dischargers in southern California were analyzed for sterols. Specifically, the fecal sterols, coprostanols (coprostanol and epicoprostanol), were quantitated to determine the degree of sewage addition to the sediment. Although coprostanols are distributed throughout the Santa Monica Basin sediments in association with fine particles, some stations contain elevated levels, either due to their proximity to the outfalls or because of preferential advection of fine-grained sediments into their location where anoxicity aids in better preservation. The progressive seaward decline of coprostanols relative to total sterols from the outfalls represents dilution of sewage by biogenic sterols. The ratio of coprostanols to dinosterol appears to be a better indicator of the degree of sewage addition. A rapid increase in content of coprostanols from about 1935 coincides with the start of offshore wastewater discharge by JWPCP, the Los Angeles County Sanitation Districts on Palos Verdes Shelf. It is estimated that wastewater treatment plants release into southern California Bight 260 metric tons/yr of fecal sterols and 5 × 104 metric tons/yr of sewage carbon. © 1990, American Chemical Society. All rights reserved.