The natural petroleum hydrocarbon background in subtidal sediments of prince william sound, Alaska, USA

Abstract

Abstract-A natural regional petroleum hydrocarbon background has been identified in the subtidal sediments of Prince William Sound that is readily distinguished from Exxon Valdez spill oil by chemical fingerprinting methods. This hydrocarbon background is derived from natural petroleum seeps in the eastern Gulf of Alaska. The Alaska Coastal Current carries fine-grained sediments and associated hydrocarbons from seep areas to the east into Prince William Sound, where they are deposited on the seafloor. The analysis of age-dated sediment cores indicates that this process has been going on for the past 160 years, and probably for many thousands of years. In addition, results of a stratified random study of nearshore subtidal sediments conducted in 1990 show that this is a general phenomenon throughout the sound and is significant even in shallow water (3 to 30 m). For example, oleanane, a saturate petroleum biomarker found in Prince William Sound prespill background petroleum and seep sources but not in Exxon Valdez petroleum, is present in subtidal sediment samples from locations throughout the sound. This supports the conclusion that seep areas to the east are major sediment sources for the sound. Moreover, polycyclic aromatic hydrocarbon mixing model calculations show that, although Exxon Valdez spill-oil residues are present in nearshore subtidal sediments, they generally form a small increment on the natural background. The recognition of preexisting natural and anthropogenic hydrocarbon sources in a spill area is a fundamentally important component of any natural resource damage assessment.

Cytochrome P4501A biomarker indication of oil exposure in harlequin ducks up to 20 years after the Exxon Valdez oil spill

“…Several authors [30][31][32][33] have argued that non-Exxon Valdez sources of PAHs are more abundant and more likely to induce CYP1A responses than residual Exxon Valdez oil. However, the spatial correspondence between elevated CYP1A induction and history of contamination during the Exxon Valdez oil spill strongly suggests causation.…”

Unexpectedly high mortality in Pacific herring embryos exposed to the 2007 Cosco Busan oil spill in San Francisco Bay

“…Sulfur-containing dibenzothiophenes are petrogenic PACs and often used for characterizing sources of oil in the environment (23)(24)(25)(26). Although Cosco Busan bunker oil is low in sulfur compared with other fuels, with a C2-dibenzothiophene/C2-phenanthrene ratio of 0.26, the alkyl-dibenzothiophenes are nevertheless one of this bunker oil's most abundant identified PAC classes.…”

Natural background and anthropogenic inputs of polycyclic aromatic hydrocarbons (PAH) in sediments of South-Western Barents Sea

“…In the marine environment, the sources of these compounds may be both natural, such as oil seeps from oil reservoirs or hydrocarbon source rocks, and anthropogenic, due to oil spills (e.g. Page et al, 1996).…”

“…Levels of PAH found in this study will also serve as a baseline for the future when extensive oil exploitation begins in the region. It has been demonstrated on several occasions that in environmental damage assessments it is very useful to have information about sources of hydrocarbons present in the affected area before activities or accidents took place (for example, see Page et al, 1996, and other studies of Exxon Valdez disaster).…”