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      Recalcitrance and degradation of petroleum biomarkers upon abiotic and biotic natural weathering of Deepwater Horizon oil.

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          Abstract

          Petroleum biomarkers such as hopanoids, steranes, and triaromatic steroids (TAS) are commonly used to investigate the source and fate of petroleum hydrocarbons in the environment based on the premise that these compounds are resistant to biotic and abiotic degradation. To test the validity of this premise in the context of the Deepwater Horizon disaster, we investigated changes to these biomarkers as induced by natural weathering of crude oil discharged from the Macondo Well (MW). For surface slicks collected from May to June in 2010, and other oiled samples collected on beaches in the northern Gulf of Mexico from July 2010 until August 2012, hopanoids with up to 31 carbons as well as steranes and diasteranes were not systematically affected by weathering processes. In contrast, TAS and C32- to C35-homohopanes were depleted in all samples relative to 17α(H),21β(H)-hopane (C30-hopane). Compared to MW oil, C35-homohopanes and TAS were depleted by 18 ± 10% and 36 ± 20%, respectively, in surface slicks collected from May to June 2010, and by 37 ± 9% and 67 ± 10%, respectively, in samples collected along beaches from April 2011 through August 2012. Based on patterns of relative losses of individual compounds, we hypothesize biodegradation and photooxidation as main degradation processes for homohopanes and TAS, respectively. This study highlights that (i) TAS and homohopanes can be degraded within several years following an oil spill, (ii) the use of homohopanes and TAS for oil spill forensics must account for degradation, and (iii) these compounds provide a window to parse biodegradation and photooxidation during advanced stages of oil weathering.

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          Author and article information

          Journal
          Environ Sci Technol
          Environmental science & technology
          American Chemical Society (ACS)
          1520-5851
          0013-936X
          Jun 17 2014
          : 48
          : 12
          Affiliations
          [1 ] Department of Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution , Woods Hole, Massachusetts 02543, United States.
          Article
          10.1021/es500825q
          24831878
          3d96d3d4-0879-424c-87cb-feb1410157f9
          History

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