Background polycyclic aromatic hydrocarbons in surface soil in the United States

It has long been recognized that polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment from a number of natural and anthropogenic sources. Several studies in the U.S. and Europe have indicated that the concentrations of PAHs in urban surface soils can range from the low parts per billion to hundreds of parts per million (EPRI, 2000) depending on the proximity to and contribution from PAH sources. PAHs in surface soil can represent human and ecological risks, and can be a substantial factor in the cost of site cleanups. Although there are many literature references concerning the presence of PAHs in environmental media, including surface soils, there is a lack of consistent data on distributions and concentrations of PAHs in surface soils because of varying sampling and analytical methodologies. EPRI is conducting a consistent nationwide assessment of PAHs in urban surface soil from hundreds of sites using a random sampling scheme. Samples have been collected from two depths, 0 - 2.54 cm and 2.54 - 15.2 cm, and analyzed for 40 PAHs and alkylated PAH groups by gas chromatography with mass spectrometry (GC/MS). The resulting data will be used to better understand how these concentrations compare to concentrations found in the soils from industrial facilities of interest, including former manufactured gas plants. Based on a review of the literature (EPRI, 2000) and the samples collected to date, PAHs from anthropogenic sources are widespread. Further, the concentrations of PAHs in urban surface soils appear to be higher than suspected. For example, in one urban area, all 40 PAHs and alkylated PAH groups were detectable in most samples above a detection limit of 5 mug/kg. The distribution was generally lognormal with an average concentration of 10,000 mug/kg.