Petroleum Residues in the Sargasso Sea and on Bermuda Beaches

Abstract

ABSTRACT Petroleum residues (“tar lumps”) are found throughout the Atlantic Ocean. An estimate of the current standing stock of tar in the Northwest Atlantic is 86,000 metric tons, of which 66,000 tons are found in the Sargasso Sea. Although there are wide seasonal variations, the amount observed near Bermuda has not increased significantly from 1971 to 1972. Beach deposits also undergo wide variations (4 g/m to 1700 g/m), and seem to act, on the average, as collectors of tar from a strip of water about 20 km wide. Chemical characteristics of tar lumps (analyzed by gas chromatography) vary widely, but almost all have distinctive paraffinic wax components in the C30 to C40 range, implying that their origin is in crude oil sludge from tanker washings. The standing stock is probably between 20 to 50 percent of the total annual influx of petroleum from this source. Degradation of tar lumps at sea, after rapid losses by evaporation and dissolution, takes times of the order of years, probably because of their substantial content of high-melting point waxes and asphaltenes.