Allen D. Uhler

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.

Peer reviewed: environmental forensics unraveling site liability.

An interdisciplinary analytical approach can unravel environmental liability at contaminated sites.

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.

Recognition of and Allocation Among Multiple Sources of PAH in Urban Sediments

Abstract The presence of polycyclic aromatic hydrocarbons (PAH) in urban sediments around the U.S. is well established. The toxic, mutagenic, and carcinogenic characteristics attributed to this class of hydrocarbons typically warrant their close monitoring, removal (e.g., dredging), or isolation (e.g., capping) in order to protect or revitalize the local urban environments. The high costs and other liabilities associated with any remedial action of urban sediments, combined with the common occurrence of multiple potentially responsible parties (PRPs) with properties bordering urban waterways, is a recipe for legal wrangling among PRPs. Environmental forensic investigations, conducted appropriately, provide the insight necessary to defensibly identify both historic and/or current, point and non-point sources of PAH to an urban water bodys sediments. The results from such investigations are sufficiently robust to support technical allocation strategies for determining responsibility among PRPs involved in oil spill assessments, Superfund allocation issues, 3rd party claims, or natural resource damage assessments (NRDA).

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.

On the Role of Process Forensics in the Characterization of Fugitive Gasoline

The need to determine the source(s) of fugitive gasoline in the environment is common when multiple candidate sources co-exist nearby to the discovery or when gasoline is discovered subsequent to a property transfer. Process forensics is the component of environmental forensics that relies upon a detailed understanding of the current and historic refining and engineering practices and how these practices would predictably have affected the chemical composition of the automotive gasoline manufactured at different refineries at different times. Since not all gasoline is ‘created equal’, when the detailed “chemical fingerprint” of a fugitive gasoline in the environment is interpreted in light of process forensics, a more thorough understanding of the production practices used to refine the fugitive gasoline can emerge. In some circumstances this knowledge can help to implicate a particular source(s) of the gasoline.

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.

Chemical Characterization and Sources of Distillate Fuels in the Subsurface of Mandan, North Dakota

The source(s) of the non-aqueous phase liquid (NAPL) in the downtown area of Mandan, ND, has been investigated through a two-part study in which the detailed chemical compositions of: 1) the NAPLs from the downtown area and remote areas on a nearby rail yard (phase I), and 2) residual petroleum in vadose zone and capillary fringe soils from borings near suspected sources (phase II) have been determined. The NAPL and soils are shown to contain variably weathered middle distillate fuels. The distributions of n-alkylcyclohexanes (CHs) and relative abundance of sulfur-containing aromatics (alkyl-dibenzothiophenes), both of which are stable over the various degrees of weathering exhibited by the NAPLs in the study area, were of particular utility in characterizing these fuels. The data indicate that multiple types of middle distillate fuels exist(ed) in the downtown area, establishing multiple sources and releases to the subsurface.