John Wiley & Sons, Ltd.

Petroleum biomarkers as tracers of Exxon Valdez oil

Over the past quarter century, petroleum biomarkers persisted in sequestered Exxon Valdez oil in Prince William Sound and the Gulf of Alaska, hence the oil remained identifiable. These biomarkers are molecular fossils derived from biochemicals in previously living organisms. Novel pattern matching indicated the presence of Alaska North Slope crude oil (ANSCO) over the entire observation period at most sites (7 of 9) and distinguished this source from several other potential sources. The presence of ANSCO was confirmed with Nordtest forensics, demonstrating the veracity of the new method. The principal advantage of the new method is that it provides sample‐specific identification, whereas the Nordtest approach is based on multi‐sample statistics. Biomarkers were conserved relative to other constituents, thus concentrations (per g oil) in initial beach samples were greater than those in fresh oil because they were lost more slowly than more labile oil constituents such as straight‐chain alkanes and aromatic hydrocarbons. However, biomarker concentrations consistently declined thereafter (1989 to 2014), though loss varied substantially among and within sites. Isoprenoid loss was substantially greater than tricyclic triterpane, hopane, and sterane loss. This article is protected by copyright. All rights reserved

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