Gregory S. Douglas

17.alpha.(H)-21.beta.(H)-hopane as a conserved internal marker for estimating the biodegradation of crude oil

Hopanes are common constituents of crude oils, and they are very resistant to biodegradation. They can therefore serve as conserved internal standards for assessing the biodegradation of the more degradable compounds in the oil. Here we address two important questions that attend such use. The first is whether the [open quotes]internal standard[close quotes] is being created during the biodegradation process itself, for this could result in an overestimate of the extent of biodegradation. The second is whether the internal standard is indeed relatively resistant to biodegradation on time scales of relevance to the biodegradation process under study; for if it was not, this could result in an underestimate of the extent of biodegradation. We find that 17[alpha](H),21[beta](H)-hopane is neither generated nor biodegraded during the biodegradation of crude oil fractions on time scales relevant to estimating the cleansing of oil spills, and so it has the appropriate characteristics to serve as an internal standard for studying the biodegradation of crude oil in the environment. 20 refs., 4 figs.

Pyrogenic polycyclic aromatic hydrocarbons in sediments record past human activity : A case study in Prince William Sound, Alaska

Polycyclic aromatic hydrocarbons (PAH) are sensitive recorders of past human activities in Prince William Sound, Alaska. In the nearshore subtidal sediments of bays, the fingerprints of the pyrogenic (combustion-derived) PAH record numerous sites of both present and historical human activities including active settlements, fish hatcheries, fish camps and recreational campsites, in addition to abandoned settlements, canneries, sawmills, and mining camps. In instances, there are high levels of PAH attributable to past human activities even though there is little remaining visual evidence of these activities on the shorelines. Forest fires are also an important source of pyrogenic PAH in subtidal sediments at certain time periods and locations and pyrogenic PAH from atmospheric fallout forms part of the regional PAH background. These pyrogenic PAH fingerprints are superimposed on a regional background of natural petroleum hydrocarbons derived from seeps in the eastern Gulf of Alaska. In isolated locations, weathered traces of the Exxon Valdez oil spill were detected as a minor part of the total PAH present from all sources.

Application of petroleum hydrocarbon chemical fingerprinting and allocation techniques after the Exxon Valdez oil spill

Advances in environmental chemistry laboratory and data interpretation techniques (i.e. chemical fingerprinting) contributed to a better understanding of the biological impact of the 1989 Exxon Valdez oil spill and the fate of the spilled oil. A review of the evolution of petroleum chemical fingerprinting techniques is presented followed by a summarization of how new approaches were used to characterize and differentiate among different petroleum sources in the Prince William Sound region after the spill. An assessment of the initial data suggested that multiple sources of polycyclic aromatic hydrocarbons (PAH) were present. These findings were further substantiated, even in samples of low part-per-billion PAH concentrations, by using refined and extended laboratory techniques including the analysis of saturate biomarkers. To interpret these mixtures of sources, fingerprint-analysis flow charts and source allocation techniques were developed and applied to the data, leading to the quantification of the spilled oil as a small increment on the natural hydrocarbon background in subtidal sediments.

Beyond 16 Priority Pollutant PAHs: A Review of PACs used in Environmental Forensic Chemistry

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soils and sediments, particularly in urbanized environments in which the concentrations of 16 (or so) PAHs are regulated. Distinguishing among the numerous PAH sources is of practical and legal concern and thereby is often an objective of environmental forensic chemistry studies. Studies of prospective sources and impacted soils and sediments that rely upon the 16 U.S. EPA Priority Pollutant PAHs are disadvantaged, as these few compounds generally lack the specificity to distinguish among different PAH sources in the environment. Advances in analytical and interpretive methods over several decades have shown that different PAH sources can be more defensibly distinguished using modified EPA Method 8270 that, among other improvements, measure many other polycyclic aromatic compounds (PACs) that co-occur with the Priority Pollutant PAHs in different sources and in the environment. The PACs include variously-alkylated PAHs and polycyclic aromatic sulfur heterocyclics (PASHs) homologs and individual isomers, which are herein reviewed. Collectively, these PACs provide a higher degree of specificity among PAC sources and can be used to understand the effects of weathering on PAH assemblages. Despite their diagnostic capacity, PACs should not be relied upon at the exclusion of other compound groups (e.g., petroleum biomarkers) in most environmental forensic chemistry studies. In light of these advances, source characterization studies that rely only upon the 16 (or so) Priority Pollutant PAHs warrant considerable caution.

Chemical heterogeneity in modern marine residual fuel oils

Because of their preponderant use as fuel in marine vessels, marine residual fuels are often the focus of maritime oil spill investigations. Residual fuels, often referred to generically as heavy fuel oil or HFO, pose a variety of challenges to oil spill investigators. Variability in the composition of modern heavy marine fuels provides unique opportunities for chemical “fingerprinting” of HFOs in the environment. This chapter focuses on the forensic chemistry of HFO—the most widely used of the commercial marine fuel oils—and chemical features of these fuels pertinent to oil spill investigations. Two most popular groups of heavy fuel oils, IFO 180 and IFO 380, differ largely in their blending formulas. From a forensic chemistry standpoint, it is the combination of the refining and blending processes that impose unique chemical “fingerprints” on IFO 380 HFOs, which oil spill investigators can use to identify and track spilled fuel in the environment. Gas chromatographic analysis of petroleum fuels reveals the distinctive boiling point distribution of the chromatographable hydrocarbons that compose the fuels.

Laboratory and Field Verification of a Method to Estimate the Extent of Petroleum Biodegradation in Soil

We describe a new and rapid quantitative approach to assess the extent of aerobic biodegradation of volatile and semivolatile hydrocarbons in crude oil, using Shushufindi oil from Ecuador as an example. Volatile hydrocarbon biodegradation was both rapid and complete-100% of the benzene, toluene, xylenes (BTEX) and 98% of the gasoline-range organics (GRO) were biodegraded in less than 2 days. Severe biodegradation of the semivolatile hydrocarbons occurred in the inoculated samples with 67% and 87% loss of the diesel-range hydrocarbons (DRO) in 3 and 20 weeks, respectively. One-hundred percent of the naphthalene, fluorene, and phenanthrene, and 46% of the chrysene in the oil were biodegraded within 3 weeks. Percent depletion estimates based on C(30) 17α,21β(H)-hopane (hopane) underestimated the diesel-range organics (DRO) and USEPA 16 priority pollutant PAH losses in the most severely biodegraded samples. The C(28) 20S-triaromatic steroid (TAS) was found to yield more accurate depletion estimates, and a new hopane stability ratio (HSR = hopane/(hopane + TAS)) was developed to monitor hopane degradation in field samples. Oil degradation within field soil samples impacted with Shushufindi crude oil was 83% and 98% for DRO and PAH, respectively. The gas chromatograms and percent depletion estimates indicated that similar levels of petroleum degradation occurred in both the field and laboratory samples, but hopane degradation was substantially less in the field samples. We conclude that cometabolism of hopane may be a factor during rapid biodegradation of petroleum in the laboratory and may not occur to a great extent during biodegradation in the field. We recommend that the hopane stability ratio be monitored in future field studies. If hopane degradation is observed, then the TAS percent depletion estimate should be computed to correct for any bias that may result in petroleum depletion estimates based on hopane.

Hydrocarbon Fingerprinting Methods

Abstract Virtually all environmental forensics investigations focus on addressing questions pertaining to the nature, source, age, and ownership of site-related contamination. Contamination, particularly at complex historic sites, is usually a multifarious mixture of both organic and inorganic chemicals. Thus, the forensic investigator is typically faced with “unravelling” a complicated mixture of chemicals into component parts in order to better link the chemicals to their historic origins and differentiate them from often similar types and sources of contaminants. This chapter describes advanced methods of chemical analyses that have evolved, and continue to be refined by environmental chemists to address the specific needs of the forensic investigator and focuses on arguably some of the most important organic contaminants commonly encountered in terrestrial and sediment investigations: petroleum hydrocarbons and polycyclic aromatic hydrocarbons (PAH). The details of advanced methods for the measurement of these chemicals in multiple media (water, soils, sediment, air, and biological tissues) are presented. Laboratory techniques, including sample preparation, instrumental analysis, and quality control and quality assurance procedures are presented so that the reader can readily adapt forensic measurement techniques to suit his or her specific site investigation activities. Case studies are presented throughout the text that demonstrate the application of advanced methods of chemical analysis to varying kinds of complicated, real world forensic instigations.

Advantages of quantitative chemical fingerprinting in oil spill source identification

The modern chemical fingerprinting analytical methods used have evolved over the past two decades, largely due to the development and increased sophistication of analytical instrumentation. The chemical fingerprinting approaches available for the identification of oil spill sources and potentially impacted samples fall into two categories: qualitative and quantitative. The qualitative approach relies upon visual comparison of various chromatographic fingerprints and is exemplified by the ASTM D3328 and D5739 methods. The cornerstone of modern petroleum fingerprinting is high-resolution capillary gas chromatography. Qualitative chemical fingerprinting analysis of spilled oil, candidate sources, and background materials can be best described as a visual comparison between various spectroscopic or chromatographic fingerprints. Such comparisons inescapably introduce a degree of subjectivity to the source identification evaluation, which is an undesirable feature of science. The quantitative approach is preferable for most oil spill investigations because the means of interpretation are more objective and robust in the sense that they facilitate numerical comparison of diagnostic details and reduce interpretation bias.

ADVANCED CHEMICAL FINGERPRINTING FOR OIL SPILL IDENTIFICATION AND NATURAL RESOURCE DAMAGE ASSESSMENTS

ABSTRACT For petroleum fingerprinting in support of natural resource damage assessments (NRDA) and other regulatory and litigation-driven scientific studies, the state of the art now focuses on polycyclic aromatic hydrocarbons (PAH) and saturated biomarker analyses, coupled with ratio and/or principal component analysis techniques, for advanced chemical fingerprinting (ACF) and allocation of petroleum mixtures to multiple sources. This strategy is being applied to oil spills, in-ground petroleum releases, and coal tar-petroleum source differentiation scenarios. The National Oceanic and Atmospheric Administrations (NOAA) draft injury guidance on NRDA recommends the application of ACF to oil spill assessments under the Oil Pollution Act of 1990.

Advantages of quantitative chemical fingerprinting in oil spill identification and allocation of mixed hydrocarbon contaminants

Abstract Detailed chemical analysis of petroleum – often referred to as “chemical fingerprinting” – has played a vital role in the identification of oil from accidental spills in the marine and riverine environments (e.g., sediments). The analytical tools used to identify and quantify the spilled oil must provide sufficient chemical resolution to separate the oil from any pre-existing (historical or naturally occurring) background hydrocarbons ubiquitous in many environments. Qualitative chemical fingerprinting analysis is a visual comparison between various spectroscopic or chromatographic fingerprints and is most successfully applied when the oil signature is unweathered and/or not mixed with other hydrocarbon sources (e.g., background). Quantitative chemical fingerprinting is the use of target compound calibration standards during the chemical analysis (e.g., GC/MS) of the sample to quantify the concentrations of source diagnostic hydrocarbons such as polycyclic aromatic hydrocarbons and biomarkers (e.g., triterpanes and steranes). These quantitative results can then be used to develop interpretive tools, such as diagnostic ratios, that allow the forensic scientist to compare spill and source oils and also to develop mixing models capable of allocating hydrocarbons derived from the spilled oil versus any background hydrocarbon signatures. Although the utility of diagnostic ratios has been discussed extensively in regard to oil spill identification in the scientific literature, the same is not true for the development and application hydrocarbon mixing models at oil spill sites. This chapter examines the applications and limitations of qualitative and quantitative oil fingerprinting methods and provides four oil spill case studies where mixing models were used to identify and or allocate liability in complex mixtures of spilled oils and various forms of background hydrocarbons.