Source of polycyclic aromatic hydrocarbon in roadway and stormwater system maintenance residues

Abstract

Soil and sediments adjacent to roadways often contain elevated concentrations of polycyclic aromatic hydrocarbons (PAHs). The sources of these PAH compounds include atmospheric deposition from automobile emissions and abraded bituminous asphalt particles from paved roads. Research was conducted to evaluate the relative contribution of each source on PAH concentrations in roadway-impacted soil and sediments by examining size fractionation and associated PAH content in roadway and stormwater system residuals. Analysis of five fractions ( 425 μm) of roadway and storm system residuals yielded varied results among the samples. The total PAH concentrations in the fractions ranged from 45 to 24,800 μg/kg with PAHs being most often encountered in the fine ( 425 μm size fractions were 1070–21,100, 609–24,800, 185–22,500, 110–16,900, and 45–7730 μg/kg, respectively. The highest concentration of individual PAH detected in the size fractions was benzo(g,h,i)perylene (6050 μg/kg) in one catch basin sediment sample. Although abraded asphalt particles from roadways were likely a source of PAHs in the coarse fractions, the predominance of PAH in the fine or median coarse size fractions suggests that other pathways such as atmospheric deposition from vehicle emissions are the major contributor. Additionally, calculated ratios between selected PAH analogs with molecular masses 178, 202, 228 and 276 also support the inference that atmospheric deposition from combustion is a major source of PAHs.