| Abstract: | Oil spills of unknown origin, so-called “mystery” spills, occur routinely in rivers, open water, and navigable coastal waterways. The natural resources damage (NRD) liability associated with even a small volume of oil released into the environment warrants that a thorough chemical characterization of the spilled oil be conducted by agencies and potentially responsible parties (PRPs). Chemical fingerprinting methods have played an important role in the identification of mystery oil spills. These methods fall into two categories, viz., qualitative and quantitative. The qualitative approach relies upon visual comparison of various chromatographic fingerprints obtained by GC/FID and GC/MS analysis of spill and candidate source oils and are represented ASTM methods. The quantitative approach relies upon measurements of the concentrations (relative or absolute) of dozens of diagnostic chemicals, typically PAHs and biomarkers, and a subsequent statistical or numerical analysis of various diagnostic parameters calculated from these concentrations. The quantitative approach is represented by the revised Nordtest methodology. The quantitative approach is preferable for most oil spill investigations since the means of interpretation are objective, whereas the ASTM methods are subjective. Quantitative fingerprinting data are particularly important when the mystery spill and source oils are qualitatively similar and are required when mystery spills may include mixed sources or prespill oil signatures. |
