Survey of the distribution and sources of PAHs in urban surface soils

Abstract

It has long been recognized that urban surface soils contain various amounts of polycyclic aromatic hydrocarbons (PAHs). Several studies in the US and Europe have indicated that the concentrations of PAHs in surface soils can range from the low parts per billion to hundreds of parts per million depending on the proximity to and contribution from PAH sources. This paper presents the results of a study of PAHs in urban surface soil in the United States. The study was a collaborative effort between EPRI, seven electric utilities, META Environmental, Inc., the state environmental agencies in New York, Illinois, and Pennsylvania, and many municipalities. Surface soil samples from 319 sites in 29 population centres in three states were collected and analysed for PAHs. Site selection was conducted using a pseudo-random sampling scheme. The samples were collected from 0 to 15.2 cm (0 to 6 inches). At some locations, samples were collected from two depths, 0 to 2.54 cm and 2.54 to 15.2 cm. The samples were analysed for 43 PAHs and alkylated PAHs by GC/MS. The concentrations of total PAHs ranged from 84 µg/kg to 147 000 µg/kg with an average concentration of 7330 µg/kg total PAHs and a median concentration of 1960 µg/kg. All 43 PAHs were detectable in most samples above a detection limit of 5 µg/kg; however, PAH concentrations were dominated by a few high molecular weight parent compounds. EPA residential risk based concentrations (RBCs) were exceeded for one or more compounds in more than 60% of the samples tested.