Petroleum Inputs Research Articles

Contribution of Chronic Petroleum Inputs to Narragansett Bay and Rhode Island Sound Sediments

Sediment cores from Narragansett Bay and Rhode Island Sound have been analyzed for petroleum hydrocarbons and compared with a relatively unpolluted sediment core from the Gulf of Maine. The sediments were analyzed for unbound hydrocarbons, hydrocarbons bound or closely associated with humic substances, and residual hydrocarbons bound or closely associated with the clay mineral or kerogen matrix. Results indicated that in general 90–100% of the hydrocarbons were in the unbound form and could be easily extracted with organic solvents. The petroleum hydrocarbons decreased with depth at all stations. Biogenic hydrocarbons (nC25, nC27, nC29, and nC31) made up an increasingly greater percentage of the total with increasing depth. The hydrocarbons in the Narragansett Bay sediments and near surface Rhode Island Sound sediments strongly resembled the hydrocarbons previously reported for the Providence River and upper Narragansett Bay. These petroleum-like hydrocarbons were shown to be largely introduced to the river and bay through chronic inputs from a municipal wastewater treatment plant. These hydrocarbons then undergo sedimentation throughout the entire bay and into Rhode Island Sound. Preliminary calculations indicate that over 0.2 million t (tonne) of petroleum hydrocarbons may be transported to the marine environment annually from municipal treatment plants. Most of these hydrocarbons appear to accumulate in estuarine and coastal sediments. Key words: hydrocarbons, petroleum, chronic pollution, Narragansett Bay, sediments

Long-term chemical effects of petroleum in south Louisiana wetlands—I. Organic carbon in sediments and waters

The chemical effects of chronic petroleum input into a shallow water marsh were examined by measuring hydrocarbon levels and dissolved organic carbon content of sediments associated with two active oil fields in south Louisiana. Annual levels of total organic carbon in the surface waters of the oil fields were higher by 1 mg C/l. in the salt marsh and 5 mg C/l. in the fresh marsh than the respective controlsites. Average dissolved organic carbon concentrations in the interstitial waters of cores taken within the oil field environments were 105% higher than the control in the salt marsh and 43% higher than the control in the fresh marsh. Significantly lower ratios of C 17 to pristane occurred in both oil field sediments; however, average odd-even predominance values were not indicative of petroleum contaminated sediments. The results indicate that microbial processes are responsible for dissolution of petroleum into dissolved organic carbon and that dissolved organic carbon concentrations may be a more significant measure of chronic petroleum input than hydrocarbon distribution.

Estimate of Annual Input of Petroleum to Marine Environment from Natural Marine Seepage: ABSTRACT

Part of the oil now present in the world's oceans results from the direct discharge of submarine seeps into the water. Proper assessment of the present hydrocarbon load carried by the oceans, as well as the evaluation of the proportion contributed by other sources (both natural and by man), requires a reliable estimate of the yearly worldwide seepage rate from marine seeps. Although only a few marine oil seeps presently are known and located, all evidence suggests that with further investigation, many more will be found. In view of the limited observations, only a few cursory estimates of total worldwide annual-marine seepage have been made; there appears to be no substantiation for any of these estimates. This paper, which represents a first documented approach based o geologic considerations, presents an estimate of yearly oil input into the oceans from naturally occurring marine seepage. A geologic model based on structural styles, recent earthquake activity, and sediment thicknesses was used to classify the continental margins into areas of high-, moderate-, and low-seepage potential. Flow-rate data for each of the 3 type potential areas were fitted to a log-normal probability distribution and seepage volumes were determined. The probable range of seepage into the marine environment is 0.2 to 6.0 million metric tons per year. Within this range the best estimate for present marine seepage worldwide is 0.6 million metric tons per year. Based on this estimate, areas of high-seepage potential contribute about 45% of the worldwide seepage. In the Pacific Ocean, high-seep potential areas are by far the major contributors. In the Atlantic and Indian oceans, moderate-seep potential areas are most significant. The circum-Pacific area is the area of greatest seepage; it is estimated to contribute about 40% of the world's total. End_of_Article - Last_Page 1840------------