Distribution, toxicity, and origins of polycyclic aromatic hydrocarbons in soils in Ulsan, South Korea

This study was conducted to investigate the concentrations, distributions, toxicities, and sources of polycyclic aromatic hydrocarbons (PAHs) in the soils from different areas in Ulsan, South Korea. Samples were collected from 41 sites, including a waste treatment facilities area (WA), traffic facilities area (TA), child playground area (CA), industrial area (IA), railroad facilities area (RA), ore and iron scraps fields area (OA), and residential area (ReA). Ulsan was chosen for research area because it used to be an environmental hot spot in South Korea, and 16 PAHs in the US EPA priority pollutant list were selected. The concentration of total PAHs (t-PAHs) ranged from 61.7 to 12,421 μg/kg, and the average concentration of t-PAHs was 706.9 μg/kg. The distribution of PAHs by ring number indicated that the portion followed the order of 4 rings > 5 rings > 3 rings > 6 rings > 2 rings. According to PAH origin indices, LMW/HMW (low molecular weight 2–3 ring PAHs over high molecular weight 4–6-ring PAHs), phenanthrene/anthracene ratio and fluoranthene/pyrene ratio, benzo(g,h,i)perylene/indeno (1,2,3-c,d)pyrene ratio, vehicular emissions, and the combustion of fossil fuel were the sources of PAHs. The strong correlation (R2 = 0.995) between t-PAHs and total carcinogenic PAHs (t-PAHcarc) indicated that the concentration of t-PAHcarc increased in proportion with that of t-PAHs. The toxic equivalent concentrations (TEQs) of PAHs in the soils ranged from 44.0 to 1929.9 μg TEQ/kg. It is imperative to set regulatory levels for PAHs for periodic monitoring and rapid remediation action of contaminated soils, because there are no national standards in South Korea for 15 PAHs with the exception of benzo(a)pyrene.