Polycyclic aromatic hydrocarbons (PAHs) in urban soils of the megacity Shanghai: Occurrence, source apportionment and potential human health risk

A comprehensive investigation was conducted to the urban soil in the megacity Shanghai in order to assess the levels of PAHs and potential risks to human health, to identify and quantitatively assess source contributions to the soil PAHs. A total of 57 soil samples collected in main urban areas of Shanghai, China were analyzed for 26 PAHs including highly carcinogenic dibenzopyrene isomers. The total concentrations ranged from 133 to 8650 ng g− 1 for Σ26PAHs and 83.3 to 7220 ng g− 1 for Σ16PAHs, with mean values of 2420 and 1970 ng g− 1, respectively. DBalP and DBaeP may serve as markers for diesel vehicle emission, while DBahP is a probable marker of coke tar as distinct from diesel emissions. Six sources in Shanghai urban area were identified by PMF model; their relative contributions to the total soil PAH burden were 6% for petrogenic sources, 21% for coal combustion, 13% for biomass burning, 16% for creosote, 23% for coke tar related sources and 21% for vehicular emissions, respectively. The benzo[a]pyrene equivalent (BaPeq) concentrations ranged from 48.9-2580 ng g− 1 for Σ24PAHs, 7.02-869 ng g− 1 for Σ16PAHs and 35.7-1990 ng g− 1 for Σ4DBPs. The BaPeq concentrations of Σ4DBPs made up 72% of Σ24PAHs. Nearly half of the soil samples showed concentrations above the safe BaPeq value of 600 ng g− 1. Exposure to these soils through direct contact probably poses a significant risk to human health from carcinogenic effects of soil PAHs. The index of additive cancer risk (IACR) values in almost one third of urban soil samples were more than the safe value of 1.0, indicating these urban soil PAHs in the study area may pose a potential threat to potable groundwater water quality from leaching of carcinogenic PAH mixtures from soil.

► The status and composition of 26 PAHs including highly carcinogenic dibenzopyrene isomers in surface soil were studied. ► Six emission sources were identified by PMF model and their relative contributions were quantitatively estimated by MLR. ► The dibenzopyrene isomers had greater carcinogenic potency than BaP in the soil samples analyzed. ► Some soil PAHs pose a significant risk to human health and potable groundwater from leaching of carcinogenic PAHs from soil.