Geochemical Patterns in Sediments Near Offshore Production Platforms

Patterns of the geochemical characteristics of sediments adjacent to three production platforms (22-150 m water depths) in the northwestern Gulf of Mexico were determined y the presence of the structure, the amount and type of materials discharged from the structure, and the local hydrographic setting. Sediments close to platforms (\u3c500m) were enhanced in coarse-grain materials primarily derived from discharged muds and cuttings. Hydrocarbon and trace metal (Ag, Ba, Cd, Hg, Pb, and Zn) contaminants were associated with these coarse-grain sediments. Contaminants were asymmetrically distributed around each platform in response to the prevailing currents. Contaminant concentrations t most locations were below levels thought to induce biological responses. At a few loctions close to one platform, trace metal (i.e., Cd, Hg) concentrations exceeded levels thought to induce biological effects. In deep water (\u3e80 m), sediment trace metal contaminant patterns were stable over time frames of years. A few metals (Pb, Cd) exhibited evidence of continued accumulation in sediments over the history of the platform