Use of Quantitative Biomarker Analysis in the Differentiation and Characterization of Spilled Oil

Abstract

The defensible identification of spilled crude oils and petroleum products and their correlation to suspected sources is a critical part of many oil spill assessments. Quantitative ‘fingerprinting’ analysis, when evaluated using straightforward statistical and numerical analyses, can provide simple yet defensible means to differentiate among qualitatively similar oils and provide the best assessment of a source(s) for spilled oils. Biomarker concentration data are a particularly useful quantitative measure that can benefit most oil spill investigations. Biomarkers' specificity, diversity, complexity, and relative resistance to weathering make them extremely useful 'markers' in the characterization and differentiation of spilled oils, any candidate source oils, and background contamination. In this paper the methodology and precision of data developed by quantitative gas chromatography-mass spectrometry operated in the selected ion monitoring mode (GCMS-SIM) is demonstrated. These data are evaluated using a statistical and numerical process that results in the defensible identification the source(s) of a spilled oil (heavy fuel oil) from among over 50 candidate sources. Introduction Oil spills of an unknown origin occur routinely in open water and navigable coastal waterways. Often these occur due to accidental or intentional discharges from vessels of dirty (oiled) ballast water, bilge waters, or tank wash slops. The tremendous liability associated with even a small volume oil spill warrants that a through chemical characterization of the spilled oil be conducted by agencies and potentially responsible parties (PRP's) in order todefensibly determine the source of the oil andquantifiably evaluate the extent of impacted ecosystems. In addition, because crude oils and refined products are often transported significant distances from their source along heavily travelled shipping lanes, the potential for a significant number of candidate ‘source’ vessels (PRP's) carrying a wide variety of chemically distinct oils is common. As a result the legally defensible differentiation and characterization of spilled crude oils and refined petroleum products is a critical part of many oil spill assessments. Qualitative chemical ‘fingerprinting’ analysis of spilled oil, candidate sources, and background materials [1–3] can in some instances sufficiently meet the need of an oil spill investigation. However, when the chemical similarity/ difference between spilled oil and candidate source oils is not obvious, the qualitative approach can be deemed subjective (biased), difficult to technically defend, and difficult to convey any complicated details to a lay decision-maker. On the other hand, quantitative chemical ‘fingerprinting’ analysis [4–6], particularly when used in conjunction with multivariate statistical analyses [6–9] can provide an unbiased and defensible means to differentiate among qualitatively similar oils. Biomarker (or biological marker) data are a particularly useful quantitative measure that can benefit oil spill investigations. Biomarkers are naturally occurring, ubiquitous and stable hydrocarbons that occur in crude oils and most petroleum products [10]. They are derived from formerly living organisms whose organic materials were preserved in oil source rocks that upon burial (heat and pressure) generated crude oil over geologic time. Their specificity, diversity, complexity, and relative resistance to weathering make them useful ‘markers’ in the characterization of spilled oils, candidate source oils, and background contamination.

Improved and Standardized Methodology for Oil Spill Fingerprinting

“…Wang et al, 1999;Stout et al, 2000) and the petroleum geochemistry literature (e.g. Wang et al, 1999;Stout et al, 2000) and the petroleum geochemistry literature (e.g.…”

“…Biomarkers' speci®city, diversity, complexity, and relative resistance to weathering therefore make them extremely useful``markers'' in the characterization and dierentiation of spilled oils and candidate source oils (Stout et al, 2000). Biomarkers are naturally occurring, ubiquitous and stable hydrocarbons that occur in crude oils and most petroleum products.…”

“…In some spill cases, it may be prudent to include a certain characteristic feature of the spilled oil that is recognized as particularly diagnostic. The¯owchart (slightly modi®ed from Stout et al, 2000; describing the suggested protocol is shown in Figure 12. Thus, maintaining¯exibility in the selection of diagnostic ratios to be used in a speci®c case study is very important.…”

Characterization of Oil by Micro-Solid-Phase Extraction and Gas Chromatography–Mass Spectrometry

“…Their source-specific structure can persist in oil, spilled oil, refinery products, and sediments, and thus can be used to track the origin of the oil spills (Stout et al 2000). The most common biomarkers used by organic geochemists include hopanes and steranes (Daling 2002).…”

A User's Guide for Determining the Sources of Contaminants in Sediments

“…The reader is directed to Stout et al (2002) for discussion on ACF techniques for automotive gasoline and other light petroleum fuels. useful in characterizing different sources of petroleum (Peters and Moldovk^an, 1993;Stout et al, 2000) and when used in conjunction with contaminant fingerprinting (e.g., PAH), these compounds can be used to distinguish contaminant sources. In the case of metals, fewer ACF techniques are available.…”