Hydrocarbon distributions around a shallow water multiwell platform
Polynuclear aromatic hydrocarbon (PAH) concentrations in nearshore coastal sediments offshore of Matagorda, TX, average 29 {plus minus} 28 (SD) ppb compared to 96 {plus minus} 112 ppb for the sediments in adjacent coastal estuaries and bays. PAHs were analyzed in bottom sediments collected in the vicinity of a multiwell platform in {approximately} 25 m of water, where six wells had been drilled between May 1982 and November 1985. The most elevated PAH concentrations were restricted to within 25 m of the platform discharge point. Mean PAH concentrations for two samplings at 10 and 25 m from the platform were 494 {plus minus} 251 and 757 {plus minus} 1,820 ppb, respectively. The contaminated platform sites ({le} 25 m distant) were dominated by two-ring aromatics while the estuarine/bay and noncontaminated coastal sites were dominated by four- and five-ring aromatic hydrocarbons. Phenanthrene/anthracene ratios suggest a petroleum source for the hydrocarbons at platform stations and pyrolytic sources for the bay/estuarine hydrocarbons.