Distinguishing PAH Background and MGP Residues in Sediments of a Freshwater Creek

Abstract

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.

Reviews of Environmental Contamination and Toxicology

“…In sediments, absence of IP has been interpreted as the absence of pyrogenic PAHs (De Luca et al 2004). Moreover, it has been shown that the use of HMW PAHs (e.g., MW = 252, benzo[k]fluoranthene, benzo[b]fluoranthene, benzo[a]pyrene, benzo[e]pyrene, benzo[j]fluoranthene, and perylene) is adequate to discriminate between different high-temperature processes, e.g., carbonization and coking in manufacturing gas plants, and combustion in motor vehicle engines (Boll et al 2008;Costa and Sauer 2005;Costa et al 2004;Ollivon et al 1999;Stout and Graan 2010).…”

Identifying sources of polycyclic aromatic hydrocarbons (PAHs) in soils: distinguishing point and non-point sources using an extended PAH spectrum and n-alkanes

“…(Brown et al 2006;Kaplan et al 2001;Marr et al 1999;Murphy and Brown 2005;Radke et al 1984;Wang and Fingas 2003). Other studies have investigated PAH contaminated soils (Stout and Wasielewski 2004;Saber et al 2006), sediments (Costa et al 2004;Saber et al 2006), and water (Costa et al 2004) located near former industrial companies (i.e., point sources, but in an environmental matrix) using aforementioned forensic methods. PAH containing atmospheric particles from wood smoke (Dos Santos Barbosa et al 2006), coal smoke (Oros and Simoneit 2000) household soot (Reddy et al 2003) and urban particulate matter (Purificación López et al 2003;Sharma and McBean 2001) were also characterized (i.e., atmospheric point sources).…”

Sediment PAH Allocation Using Parent PAH Proportions and a Least Root Mean Squares Mixing Model

“…The use of such quantitative techniques does not require a priori knowledge of the candidate sources or their profiles. Semi-quantitative techniques, such as plotting double-ratio cross plots of parent PAHs (Costa and Sauer, 2005;Costa et al, 2004;EPRI, 2000) and matching the predominant source(s) to a contaminated area(s), may also be used to discern source patterns. Parent and alkylated Costa and Sauer, 2005 Further discussion of Costa et al, 2004 (see below), including discussion of methods for selecting appropriate diagnostic ratios.…”

“…It is recognized that the selection of diagnostic PAH proportions should be based on: 1) similar structural, physical, and chemical properties, such as that afforded by the use of isomer pairs; 2) minimal effects of environmental weathering (absolute and relative); and 3) the capability to distinguish the source material(s) that are present (Zemo, 2009;Costa and Sauer, 2005;Costa et al, 2004;Lima et al, 2005;Yunker and Macdonald, 1995;Yunker et al, 2002). Higher molecular weight (i.e., 4-to 6-ringed) PAHs are typically more suitable for identifying PAH sources because they are recalcitrant to environmental weathering, particularly if entrained within a non-aqueous phase liquid (NAPL) matrix (Yunker et al, 2002;Eberhardt and Grathwohl, 2002;Peters et al, 1999).…”

“…Parent and alkylated Costa et al, 2004 Used source diagnostic ratios to distinguish urban background from MGP tar in sediments. Semi-quantitative analysis using double-ratio plots.…”