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

Abstract

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.

Errors in alkylated polycyclic aromatic hydrocarbon and sulfur heterocycle concentrations caused by currently employed standardized methods

“…Much attention is given to PAH and PASH because they are toxic [5,6] and known carcinogens [7,8], mutagens [9e11], and teratogens [12]. Scientists, engineers, and regulators worldwide rely on selective and accurate quantitation of PAH/PASH to support hazardous waste site investigations and environmental forensics [13,14], weathering [15,16] and toxicity studies [17,18].…”

Estimating PAH sources in harbor sediments using diagnostic ratios

“…Polycyclic aromatic hydrocarbons (PAHs) are notoriously present in marine sediments all over the world (Lima, Farrington, & Reddy, ; Stout, Emsbo‐Mattingly, Douglas, Uhler, & McCarthy, ). In aquatic environments, the hydrophobic nature of PAHs can lead to long‐term persistence and subsequent accumulation in sediments (Jiao et al, ; J. Li et al, ; Wu et al, ).…”

“…Elevated PAH concentrations has been documented in large, commercial Canadian harbors, including Vancouver Harbor (British Columbia), Halifax Harbor (Nova Scotia), Sydney Harbor (Nova Scotia), and Saint John Harbor (New Brunswick; Bolton et al, ; Tay et al, ; Walker, Gray, et al, ; Walker, MacAskill, & Weaver, ; Zitko, ) and in small craft harbors (SCHs; Davis, Walker, Adams, & Willis, ; Walker, MacLean, Appleton, McMillan, & Miles, ), rural sites which support various fisheries in Nova Scotia (Walker, MacLean, et al, 2013; Zhang, Walker, Davis, & Guofeng, ). As PAHs can demonstrate carcinogenic, mutagenic, and toxic properties, they are considered contaminants of concern in many nations (Tobiszewski & Namieśnik, ; US Environmental Protection Agency US EPA, ; Stout et al, ). In Canada, PAH concentrations are regulated in various environments, and subsequent environmental quality guidelines exist for individual and total PAHs (e.g., Canadian Council of Ministers of the Environment [CCME] sediment quality guidelines, Canadian Environmental Protection Act Disposal at Sea Regulation Guidelines).…”

“…In Canada, PAH concentrations are regulated in various environments, and subsequent environmental quality guidelines exist for individual and total PAHs (e.g., Canadian Council of Ministers of the Environment [CCME] sediment quality guidelines, Canadian Environmental Protection Act Disposal at Sea Regulation Guidelines). As such, forensic assessment of PAHs is an important practical, legal, and environmental consideration in support of what emission sources may be contributing to the environment and the determination of financial and/or environmental liabilities of PAH source(s) (Stout et al, ; MacAskill et al, ).…”

“…Diagnostic ratios are a commonly applied cost‐effective tool for risk assessors and remediation practitioners to assess PAH sources and can be used as a singular line of evidence or as part of a multifaceted approach that incorporates multiple techniques (Budzinski, Jones, Bellocq, Pierard, & Garrigues, ; Yunker et al, ; Sofowote et al, ). Diagnostic ratios are applied with the understanding that PAH sources produce different PAH profiles that show variable proportions of individual PAH compounds (Stout et al, ). Specifically, high and low temperature PAH emission processes will yield varying PAH profiles, and application of diagnostic ratios can help in distinguishing whether sources are pyrogenic or petrogenic in origin (Tobiszewski & Namieśnik, ; Stout et al, ).…”