Evaluation of biodegradability of hydrocarbon biomarkers in a field trial for oil-contaminated shoreline bioremediation

Bioremediation is one of the most cost-effective techniques to clean up oil-contaminated soils and sediments. Due to the heterogeneity of oil distribution in soil/sediment, non-biodegradable or relatively degradation-resistant hydrocarbon biomarkers have been commonly used as conserved internal standards to correct for the non-biodegradation loss of oils and sampling errors. However, little is known about the biodegradability of these biomarkers in the field. The lack of this knowledge could underestimate the degradation rate of oil in soil/sediment. In this study, the biodegradation of several commonly used biomarkers (pristine, phytane, steranes, and hopanes) in simulated oil spill shoreline was examined under different conditions: 1) oil only, 2) oil + water-soluble nutrients, 3) oil + slow-release nutrients, and 4) oil +slow-release nutrients + oil-degrading bacteria. Significant degradation of pristine, phytane and C-27-C-29 steranes was observed over the 90-day incubation at all treatments. Compared to the other tested biomarkers, 17 alpha (H), 21 beta (H)-hopane (C-30 alpha beta) and its homologues, presented a much stronger resistance to biodegradation. Based on the results of this study, we suggest using C-30 alpha beta as conserved internal standard in the study of oil remediation on shoreline field trials.