Contributions of common sources of polycyclic aromatic hydrocarbons to soil contamination



Asphalt products, particularly sealants, are prepared using petroleum products that contain a com-plex mixture of aliphatic and aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs). Clearly, these products are ubiquitous in urban environments, which raises an issue regard-ing the potential for PAHs to be transported from parking lots to underlying or adjacent soil, surface-water bodies, or groundwater. Based on a literature review, there are limited studies focus-ing on this issue; however, the studies that have been published have fascinating conclusions. The literature shows, as expected, that asphalt-based products contain PAHs. The highest PAH concen-trations are present in asphalt sealants, particularly those manufactured using coal tar. Furthermore, due to the low solubility and high partition coefficients of PAHs, the potential for PAHs to leach from asphalt surfaces is negligible, which has been confirmed by leachability studies. Thus, there is little risk that PAHs will be present in stormwater runoff or leach into groundwater from asphalt-paved areas in a dissolved form. However, asphalt pavement and sealants produce particulate matter that can contain concentrations of PAHs in the sub-percent range (100s to 1,000s mg/kg total PAHs) that is transported in stormwater runoff. Some studies show that this can cause soil and sediment con-tamination with total PAH concentrations in the range of 1 to 10 mg/kg. From a remediation per-spective, many site cleanups are conducted to remediate the presence of PAHs to cleanup goals below 1 mg/kg or, in some cases, 0.1 mg/kg or lower. From a total risk perspective, remediating sites to low PAH cleanup goals may be unwarranted in light of the risk of transportable PAHs produced from paved parking surfaces. In other words, is it reasonable to conduct a cleanup to remediate low PAH concentrations and then redevelop the area with asphalt pavement and sealant, which may pose a greater PAH-related risk? © 2006 Wiley Periodicals, Inc.