Petroleum-related contaminants near a produced water discharge site in the Santa Barbara Channel

Offshore oil production generates substantial quantities of waste water that is frequently discharged into marine waters. Contamination of coastal sediments occurs due to other inputs including natural petroleum seeps, and this complicates assessments of the environmental effects of produced water in marine ecosystems. The current study has focused on characterization of contaminants in sediments near produced water discharge site off the coast of Southern California. First, it was important to address the question: ''What contaminants in sediments should be monitored as indicators of produced water effects?'' Dichloromethane extracts of sediments were analyzed for numerous organic constituents using gas chromatography-mass spectrometry and selected ion monitoring. Though the phenols and fatty acids were not detected in sediment extracts, normal and branched alkanes and other petroleum hydrocarbon biomarkers were quantified. No relationship was evident that related absolute concentrations of organic compounds to distance from the outfall, but patterns of petroleum hydrocarbons exhibited consistent spatial variations that could be related to distance from the produced water out fall. Analysis of chemical fossil ''biomarkers'' provides potentially useful indices of effects of waste discharges upon microbial biodegradation of organic compounds in sediments