Stephen D. Emsbo-Mattingly

Gas emissions, minerals, and tars associated with three coal fires, Powder River Basin, USA.

Ground-based surveys of three coal fires and airborne surveys of two of the fires were conducted near Sheridan, Wyoming. The fires occur in natural outcrops and in abandoned mines, all containing Paleocene-age subbituminous coals. Diffuse (carbon dioxide (CO(2)) only) and vent (CO(2), carbon monoxide (CO), methane, hydrogen sulfide (H(2)S), and elemental mercury) emission estimates were made for each of the fires. Additionally, gas samples were collected for volatile organic compound (VOC) analysis and showed a large range in variation between vents. The fires produce locally dangerous levels of CO, CO(2), H(2)S, and benzene, among other gases. At one fire in an abandoned coal mine, trends in gas and tar composition followed a change in topography. Total CO(2) fluxes for the fires from airborne, ground-based, and rate of fire advancement estimates ranged from 0.9 to 780mg/s/m(2) and are comparable to other coal fires worldwide. Samples of tar and coal-fire minerals collected from the mouth of vents provided insight into the behavior and formation of the coal fires.

Weathering of field-collected floating and stranded Macondo oils during and shortly after the Deepwater Horizon oil spill

Chemical analysis of large populations of floating (n=62) and stranded (n=1174) Macondo oils collected from the northern Gulf of Mexico sea surface and shorelines during or within seven weeks of the end of the Deepwater Horizon oil spill demonstrates the range, rates, and processes affecting surface oil weathering. Oil collected immediately upon reaching the sea surface had already lost most mass below n-C8 from dissolution of soluble aliphatics, monoaromatics, and naphthalenes during the oils ascent with further reductions extending up to n-C13 due to the onset of evaporation. With additional time, weathering of the floating and stranded oils advanced with total PAH (TPAH50) depletions averaging 69±23% for floating oils and 94±3% for stranded oils caused by the combined effects of evaporation, dissolution, and photo-oxidation, the latter of which also reduced triaromatic steroid biomarkers. Biodegradation was not evident among the coalesced floating oils studied, but had commenced in some stranded oils.

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.

An Integrated Case Study for Evaluating the Impacts of an Oil Refinery Effluent on Aquatic Biota in the Delaware River: Advanced Chemical Fingerprinting of PAHs

ABSTRACT More than one thousand samples were collected and analyzed to evaluate the potential impact of Motivas oil refinery effluent on the receiving water, sediment, and biota of the Delaware River. The data collected from these samples were used with advanced chemical fingerprinting of polycyclic aromatic hydrocarbons (PAHs) in Motivas oil refinery effluent to differentiate Motiva-related PAHs in sediment and biota from other sources. The PAHs released from the refinery between 1999 and 2002 were dominated by petrogenic 4-ring PAHs. Specifically, the refinery signature exhibited relatively high levels of fluoranthenes/pyrenes with two (FP2) and three (FP3) alkyl groups and benz(a)anthracene/chrysenes with two (BC2), three (BC3), and four (BC4) alkyl groups. This PAH signature, attributed to accelerated degradation of low molecular weight PAHs in the Motiva wastewater treatment plant, exhibited little variability over time relative to the background patterns in the Delaware River. This distinctive feature of the Motiva effluent allowed the identification of this source in other samples. Water and sediment samples identified a range of PAH characteristics associated with the Delaware River urban background signature. These characteristics included varying levels of 2- to 3-ring PAHs (likely from weathered automotive fuel, marine fuel, or bilge tank discharges), pyrogenic 4- to 6-ring PAHs (from partially combusted organic material like soot), and perylene (diagenetic product of terrestrial plant decomposition). The Motiva hydrocarbon signature was only evident at moderate to low levels in selected near-field sampling stations for sediment, bivalves, and effluent/nearfield water. PAHs in the river sediments beyond the near-field area were consistently associated with samples containing the Delaware River urban background signature, and exhibited little to no effect from the Refinery.

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.

Semivolatile Hydrocarbon Residues of Coal and Coal Tar

This chapter presents the current analytical methods used for the characterization of the semivolatile hydrocarbon source signatures of coal and coal-derived by-products. A particular focus is given to the thermally derived by-products of coal formed from its thermal decomposition by industrial carbonization (coking), which mirror the by-products formed during natural coal fires. Semivolatile hydrocarbons are solvent-extractable compounds found in coals and coal-derived by-products that include a broad range of compounds. Functionally they can be defined as solvent-extractable compounds that elute between about n-nonane (n-C9) and n-tetratetracontane (n-C44)ona gas chromatograph (GC) equipped with a nonpolar silicone capillary column. The semivolatile hydrocarbons include normal alkanes, acyclic isoprenoids, aromatics, sesqui-, di-, and triterpanes, regular and rearranged steranes, mono- and triaromatic steranes, and many other compound groups. Numbering in the thousands of individual compounds, the relative abundances or absolute concentrations of diagnostic semivolatile hydrocarbons can differentiate fossil fuels and various derived products. Sophisticated analytical methods exist for the chemical characterization of the extractable, semivolatile hydrocarbons that occur in the nonvolatile by-products produced in the course of coal fires, namely, carbonized coal residues and coal tars. Both coal fires and industrial coal carbonization plants produce by-products with hydrocarbon signatures imbued with information about the native (unburned) parent coal, the conditions of carbonization, and the weathering of the by-products in the environment (particularly volatilization). This information can prove useful in environmental investigations that involve coal carbonization by-products.

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.

Characterization of PAH Sources in Sediments of the Thea Foss/Wheeler Osgood Waterways, Tacoma, Washington

The character of polycyclic aromatic hydrocarbons (PAH) in sediments of the Thea Foss and Wheeler-Osgood Waterways in Tacoma, Washington, were investigated with the objective of determining the general source(s) of these compounds to the waterways. In this study, 42 near-surface sediment samples from the Waterways were collected and analyzed for their (1) concentration of 43 individual or groups of PAH, (2) total extractable hydrocarbon “fingerprint” and concentration, (3) grain size and (4) total organic carbon content. Analysis of the sediment data, including comparisons to standard reference materials, indicates that all but two samples contained PAH derived from a pyrogenic source(s), i.e., a non-petroleum source(s). The high concentrations and characteristic distributions of PAH in some sediment samples were consistent with the occurrence of manufactured gas plant (MGP) derived tar(s) or tar distillate(s), particularly in some sediments proximal to a historic MGP and tar distillate storage operation near the head of the Thea Foss Waterway. Most other sediment samples throughout the Waterways contained PAH distributions and concentration indicating (at least) a greater proportion of PAH are derived from urban runoff/fallout.

Identifying the Source of Mystery Waterborne Oil Spills—A Case for Quantitative Chemical Fingerprinting

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.

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.