Sources, sinks, concentrations and sublethal effects of light aliphatic and aromatic hydrocarbons in the Gulf of Mexico

Abstract

The spatial distribution and sources of light hydrocarbons in the Gulf of Mexico are evaluated from "sniffing" surveys of over 5,000 miles of cruise tracks aboard the R/V Gyre, R/V Alaminos and R/V Miss Freeport and from over 300 discrete water samples. The surveys were performed using a modified Beckman Process Gas Chromatograph with a FID detector. The methodology of hydrocarbon "sniffing" is after Brooks et al. (1973) and the discrete analysis is after Swinnerton and Linnenbom (1967) and McAullife (1971). The six significant inputs of light hydrocarbons to the Gulf are: (1) natural seepage of oil and gas, (2) offshore drilling and production, (3) transportation losses, (4) coastal contributions, (5) air-sea exchange, and (6) biologically-derived hydrocarbons. It was found that hydrocarbon "sniffing" was a sensitive means of detecting man-derived hydrocarbon pollution. The significance of each of the major inputs is evaluated. Coastal waters of the Gulf of Mexico, in general, are not in equilibrium with the atmosphere with respect to low-molecular weight hydrocarbons. This is chiefly the result of large man-derived inputs. Offshore production and transportation activities are the chief inputs of light hydrocarbons to the coastal regions, contributing the whole spectrum of light gaseous, liquid and aromatic hydrocarbons. Coastal contributions from refineries and runoff are also significant man-derived inputs. In the deep-water Gulf of Mexico natural sources of methane and olefins in the upper few hundred meters can rival man's input of these hydrocarbons. ...