William M. Sackett

Distribution, sources and fates of floating oil residues in the Eastern Gulf of Mexico

Abstract Pelagic tar was monitored over a two-year period in the Eastern Gulf of Mexico. A total of 416 surface and subsurface samples were collected during monthly cruises. Concentrations of pelagic tar found in the Eastern Gulf of Mexico were substantially higher than values reported for other areas around the world. Tar is primarily associated with the Gulf Loop Current, whereas continental shelf areas are relatively uncontaminated. Grounding of significant amounts of tar occurs primarily along the south-east coast of Florida, between Key West and Fort Pierce. Approximately 10–50% of the tar in the eastern Gulf is transported in from the Caribbean Sea via the Yucatan Straits. The remainder originates within the Gulf. Approximately half of the pelagic tar samples collected during the study appeared to have originated from tanker operations.

δ13C signatures of organic carbon in southern high latitude deep sea sediments; paleotemperature implications

Abstract The 7% carbon-13 depletion in cold water phytoplankton provides a striking signal that is traceable in deep-sea cores taken in high latitude regions of the Southern hemisphere. This signal may be weakened by noise due to (1) terrestrially derived debris in areas close to the continents; (2) changing current patterns resulting in varying settling trajectories; (3) erosion and redeposition and (4) maturation-diagenetic effects. Data for two cores taken southwest of Australia are evaluated with respect to these interferences.

Carbon isotope effects during the pyrolytic formation of early methane from carbonaceous materials

Abstract The amounts and stable carbon isotope compositions of early methane formed during closed system pyrolysis of 4 coal samples of different ranks, 6 lipid-free shales of different maturities, and 1 topped crude oil were determined as a function of time. Except for 1 sample of anthracite coal, the isotopic compositions of the first methane were isotopically heavy relative to later formed methane. A carbon-12 rich peak was generally observed for a total accumulated methane to parent carbon mole ratio of about 0.01–0.03. These changes are discussed in terms of shifts from carbonium ion to free radical mechanisms and carbon isotope heterogeneities in the methane precursor functional groups.

Determination of kerogen maturity by the pyrolysis-carbon isotope method

Abstract The premise of the proposed maturation procedure is that immediately after post-depositional microbial alteration of organic matter there is a degradable but not renewable pool of non-extractable methane precursor carbon that becomes smaller as methane is produced with increasing time and temperature. In addition, the methane progressively becomes isotopically heavier because of mass balance and bonding considerations. A maturity index based on the isotopic difference between the total accumulated methane produced by pyrolysis and the kerogen carbon and/or the mole ratio of methane to kerogen carbon is presented. Published data by Chung and Sackett Geochim. Cosmochim. Acta43, 1979–1988 (1979) for a suite of 19 coals and 12 shales of various ranks and maturities support this procedure.

Plutonium and cesium radionuclides in sediments of the Savannah River estuary

A study was made of the 239Pu, 240Pu, 238Pu and 137Cs concentrations in tidal marsh sediments of the Savannah River estuary. Tidal marshes are identified as special locations for plutonium deposition because of the high biological productivity and relative stability of sediments as compared to channel sediments. The 239,240Pu deposition averaged 3·2 mCi km−2, which is higher than land-based fallout values of about 2 mCi km−2. The 239,240Pu to 137Cs ratio was about three times higher than fallout deposition estimates, indicating a more rapid desorption of 137Cs from sediment in the saline waters of the area.

Useful and Easy to Apply Indicators of Petroleum Pollution in the Marine Environment

Case histories of studies in the Gulf of Mexico show that: 1. Dissolved low-molecular-weight hydrocarbons (C1 to C5) are sensitive indicators of the inputs of crude petroleum and some refinery and municipal activities. 2. Stable carbon isotope compositions are indicators of crude oil residues in sediments. 3. The amounts of floating oil residues define the extent of petroleum contamination by transportation activities.