A CHEMICAL ASSESSMENT OF THE PRESENT LEVELS AND SOURCES OF HYDROCARBON POLLUTANTS IN THE GEORGES BANK REGION

Abstract

ABSTRACT Analysis of five suites of samples covering 40 stations in the region of Georges Bank, Nantucket Shoals, and the lower Gulf of Maine illustrates the ubiquity of anthropogenic hydrocarbons throughout this highly productive and heavily fished area. Petroleum compounds from a recent major oil spill (Argo Merchant) and chronic inputs from ballast washings and normal shipping traffic were evident in the water column's dissolved and particulate hydrocarbon fractions. Concentrations were generally in the 0.1 parts per billion to 2.0 ppb range throughout the year, but were above 10 ppb in the four months after spills occurred in late 1976 and early 1977. Individual polynuclear aromatic hydrocarbons (which persisted in the water column during the year at levels of one to 10 nanograms/liter, also were elevated in concentration (10 to 50 ng/l) in early 1977. Surface film enrichment in petroleum hydrocarbons was 1.5 to 90 times that of subsurface waters. This illustrates the existence of a year-round reservoir (10 to 70 ppb) for petroleum-derived material in the ocean's surface microlayer. Surface sediments contained both anthropogenic and biogenic hydrocarbons. Up to 20 micrograms/gram of chromatographically unresolved complex mixture was found in siltier sediments. The unresolved complex mixture appears to have a terrigenous source. Recent tar and oil inputs to the sediments of the region also were observed, but the chemical impact on the benthos was short-lived, station revisitation showed. Sediments contained up to 50 ng/g of individual polynuclear aromatic hydrocarbons attributable to pyrolytic sources and petroleum inputs. Analyses of whole benthic invertebrates revealed sporadic but sizeable inputs of petroleum hydrocarbons to the benthic environment. These were assimilated by such edible species as sea scallops and ocean quahogs, commonly harvested in the region.