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Polycyclic aromatic hydrocarbons (PAHs) in the environment have origins in various natural and anthropogenic sources. Pyrogenic tars (e.g., coal tar) are rich in PAHs, which are therefore typical constituents of concern at former manufactured gas plant (MGP) sites. Delineating the extent of PAHs in sediments is a common component of many former MGP remedial investigations. Because of the compositional similarity of weathered/degraded coal tar residues to combustion-related PAHs that comprise typical urban background, it can be difficult to determine the local PAH background contribution in sediments near MGP sites. This article presents an investigation of Mill Race Creek, a freshwater creek that flows adjacent to the Oneonta, New York former MGP. From the delineation sampling, elevated PAH concentrations were measured in "background" areas upstream of any suspected MGP releases. PAH fingerprinting revealed three primary PAH sources in creek sediments: low molecular weight (LMW), 2-and 3-ring PAHs from background petroleum sources; high molecular weight (HMW), 4-to 6-ring PAHs from site-related sources; and HMW PAHs from background sources. The results of this investigation demonstrated that site-related PAH residues were primarily localized in the subsurface of a few sediment deposits adjacent to the former MGP. Sediments containing site-related PAHs were generally buried underneath a surficial (6 in) layer of sediments with total priority pollutant PAH concentrations (55.0 ± 48.8 mg/kg) that were almost entirely attributable to local background sources. In the context of a remedial investigation, contributions from uncontrolled background PAHs may limit the practicable feasibility of some remedial options.

Abstract-Toxicity identification evaluations (TIEs) were performed on 14 produced-water (PW) samples of various salinities from inland and offshore oil-and gas-production facilities operated by different companies in Wyoming, Texas, California, and Louisiana (USA) to evaluate the efficacy of TIE procedures in determining potential toxicants in PW effluents. The research involved acute (24-and 48-h) freshwater and marine toxicity tests on whole PW and PW fractions generated by standard U.S. Environmental Protection Agency and PW-specific fractionation schemes. Factors influencing PW TIEs were investigated, such as the effect of salinity in selecting fractionation manipulations, the effect of toxicity test replication (i.e., reproducibility) in distinguishing changes in toxicities between whole PW and its fractions, and the suitability of different test species in PW TIEs. The results obtained and lessons learned from conducting these PW TIEs are presented in this article. Components, or fractions, contributing to toxicity differed for each PW with no specific fraction being consistently toxic. For most PW samples, toxicity attributed to any one fraction represented only part of the toxicity of the whole sample. However, no more than two fraction types were identified as potential toxicants in any sample. Potential toxicants identified during this study, besides salinity, included acidic and basic organic compound class fractions, particulates removed by filtration at pH 11, ammonia, hydrocarbons, hydrogen sulfide, material removed by pH change, and volatile compounds.

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