Natural Hydrocarbon Background in Benthic Sediments of Prince William Sound, Alaska:  Oil vs Coal

Abstract

The source of the background hydrocarbons in benthic sediments of Prince William Sound (PWS), AK, where the 1989 Exxon Valdez oil spill (EVOS) occurred, has been ascribed to oil seeps in coastal areas of the Gulf of Alaska (GOA). We present evidence that coal is a more plausible source, including (i) high concentrations of total PAH (TPAH), between 1670 and 3070 ng/g, in continental shelf sediments adjacent to the coastal region containing extensive coal deposits; (ii) PAH composition patterns of sediments along with predictive models that are consistent with coal but not oil; (iii) low ratios (<0.2) of triaromatic steranes to methylchrysenes found in sediments and coals, contrasting with the high ratios (11 and 13) found in seep oil; and (iv) bioaccumulation of PAH in salmon collected within 100 m of the Katalla oil seeps but not in filter-feeding mussels collected near oilfield drainages 9 km from the seeps, indicating negligible transport of bioavailable PAH from Katalla seeps to the GOA. In contrast with oil, PAH in coal are not bioavailable, so the presence of coal in these benthic sediments confers no adaptive benefit to biota of the marine ecosystem with respect to PAH insults from anthropogenic sources.

Analysis of polyaromatic hydrocarbon (PAH) contaminated riparian sediment and source identification

“…Chrysene is the most abundant PAH in the sediment sample. The prominence of chrysene and other 5-ring PAHs in the PAH profile is indicative of a coal origin [11]. Although no identification of the source is attempted, several industries burned coal as an energy source.…”

Exxon Valdez oil spill: impacts and recovery in the soft-bottom benthic community in and adjacent to eelgrass beds

“…For example, the average concentration of TPAHs at 6 to 20 m depth at the Lower Hernng Bay in 1990 was 1908 ng g-', but none of the samples from there had analyte signatures characteristic of weathered 'Exxon Valdez' crude oil. The TPAH Patterns were more evident of gasoline (possibly contaminated during collection), diese1 oil (possibly from cleanup activities), submarine oil seeps , or coal (Short et al 1999). …”

“…Also, sediments collected from sediment traps at Sleepy Bay in 1989 had TPAH concentrations as high as 28 000 ng g-' and were generally higher than in nearby sediments on the bottom (Short et al 1996a), suggesting that exposure to oil in suspended sediments may have been higher than the exposure to deposited sediments. Some of the hydrocarbon contarnination observed was probably the result of spill-related activities as well as coal rather than spilled 'Exxon Valdez' oil (O'Clair et al 1996, Short et al 1999. At the peak of the cleanup and monitonng activities, over 1400 vessels were involved in the effort (Carpenter et al 1991, Mearns 1996 and small accidental releases from these boats likely contributed to higher hydrocarbon concentrations.…”

“…At the peak of the cleanup and monitonng activities, over 1400 vessels were involved in the effort (Carpenter et al 1991, Mearns 1996 and small accidental releases from these boats likely contributed to higher hydrocarbon concentrations. Naturally occurring TPAH in subtidal sediments is likely from coal deposits east of the Sound; contributions from oil seeps are negligible (Short et al 1999). There is no way of knowing what proportion of the TPAHs observed were from the spiil itself, from spill-related contamination, or from naturally occurring sources.…”

Biochemical and Enzyme Responses in Rabbits Experimentally Fed Crude Oil Contaminated Diets

“…The long-term impacts are poorly understood and thus generate other environmental perturbations. Stream contamination evaluated seven years after the Exxon Valdez spill of 1989 identified hydrocarbon as potential confounding stressors in biota of spill impacted areas (Short et al, 1999).…”