Petroleum hydrocarbons, biomarker

The purpose of this chapter is to describe well-established analytical methods that are available for detecting and/or measuring and/or monitoring total petroleum hydrocarbons and their metabolites, as well as other biomarkers of the exposure and effect of total petroleum hydrocarbons. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods approved by federal agencies and organizations such as the Environmental Protection Agency and the National Institute for Occupational Safety and Health (NIOSH) or methods prescribed by state governments for water and soil analysis. Other methods... 

Petroleum hydrocarbon sources to North American and worldwide waters were summarized in a report by NRC (2002). In many cases of large petroleum spills, the specihc source of petroleum spill is evident, and no geochemical fingerprinting is required to establish the source. Nevertheless, the inventory of petroleum compounds and biomarkers that are eventually sequestered in bottom sediments need not reflect sole derivation from a single source, even in cases of massive oil spills in the area (e.g., Kvenvolden et al., 1995 Wang et al., 1999). Where a mass balance of petroleum sources is required to properly design remediation or identify a point source, molecular methods for distinguishing sources of hydrocarbons have come to the fore. 

Abdul-KassimT. A. T. and Simoneit B. R. T. (1995) Petroleum hydrocarbon fingerprinting and sediment transport assessed by molecular biomarker and multivariate statistical analysis in the eastern harbour of Alexandria, Egypt. Mar. Pollut. Bull. 30, 63-73. 

Measurements of motor and sensory nerve conduction velocities and action potential amplitudes have been proposed as sensitive preclinical biomarkers of peripheral neuropathy in workers repeatedly exposed to /7-hexane (ATSDR 1999b), but this effect is specific to //-hexane (and perhaps a few other aliphatic hydrocarbons in the EC5-EC8 fraction) among petroleum hydrocarbons. 

Chosson P, Lannau C., Connan J., Dessort D. (1991) Biodegradation of refractory hydrocarbon biomarkers from petroleum under laboratory conditions. Nature 351, 640-2. 

In response to the oil spill identification need and specific site investigation needs, attention has focused on the development of flexible, tiered analytical approaches, which facilitate the detailed compositional analysis by GC-MS, GC-FID, and other analytical techniques that quantitatively determine a broad range of individual petroleum hydrocarbons. A variety of diagnostic ratios, especially ratios of PAH and biomarker compounds, for interpreting chemical data from oil spills have been proposed. 

The application of biomarker research in the geologic record has dealt with the derivative hydrocarbons as found in petroleum, coals, and sedimentary rocks. Reports on biomarkers in discrete fossils compared to the host rocks are sparse because (1) previous studies focused on the highly degraded geoterpenoids, i.e. saturated and aromatic hydrocarbons, and (2) the preservation potential of polar compounds (natural product bioterpenoids ) was believed to be low. Flowever, recent investigations of conifer fossils demonstrated that unaltered natural product terpenoids can be preserved in resin material.This will be illustrated here with an example. 

Advances in petroleum characterization at the molecular structure level by GC-MS methods renewed interest in OSC. Within the past few years, at least one-thousand new and novel OSC that previously were not known to be present in petroleum and bitumens have been reported. Tentative molecular structures inferred from GC-MS and other techniques have been confirmed in many cases by synthesis of authentic reference-compounds. The difficult and time-consuming synthetic work has been crucial in validating many of the novel structures. Another key finding has been that immature bitumens and crude oils (samples that have not received significant thermal stress) differ markedly from the previously known OSC in that they have carbon-skeletons resembling ubiquitous biomarker hydrocarbons (e.g., n-alkanes, isoprenoid alkanes, steranes, and hopanes). This similarity, of course, suggests that the hydrocarbons and OSC have common biogenic precursors. 

The molecular distribution and compound-specific carbon-isotopic composition of hydrocarbons can be used to qualify and quantify their sources and pathways in the environment. Molecular source apportionment borrows from molecular methods that were developed and applied extensively for fundamental oil biomarker studies, oil-oil and oil source rock correlation analysis. Additionally, petroleum refinement produces well-defined mass and volatility ranges that are used as indicators of specific petroleum product sources in the environment. Compound-specific carbon-isotopic measurement is a more recent addition to the arsenal of methods for hydrocarbon source apportionment. Carbon isotopic discrimination of i-alkanes, biomarkers, and PAHs has shown that the technique is highly complementary to molecular apportionment methods. 

In recent several years, many EPA and ASTM methods have been modified (such as the modified EPA method 8015, 8260 and 8270 and the modified ASTM methods 3328-90, 5037-90 and 5739-95) to improve specificity and sensitivity for measuring spilled oil and petroleum products in soils and waters by environmental chemists. For example, EPA Method 8270 has been modified to increase analytical sensitivity and to expand the analyte list to include petroleum specific compounds such as the alkylated PAHs, sulfur, and nitrogen containing PAHs, and biomarker triterpane and sterane compounds. The principal modification to EPA Method 8270 is the use of the high resolution GC-MS selected ion mode (SIM) analysis that olfers increased sensitivity relative to the full scan mode. Many environmental laboratories have used the modified EPA Method 8270, combined with column cleanup and rigorous QA measures, to identify and quantify low levels of hydrocarbons. 

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