Levels, composition profiles and sources of polycyclic aromatic hydrocarbons in urban soil of Shanghai, China

Levels, composition profiles and sources of polycyclic aromatic hydrocarbons (PAHs) were analyzed in 55 surface soil samples collected from Shanghai urban districts. The total concentrations of 22 PAHs (ΣPAHs) ranged from 442 to 19,700 μg kg−1, with a mean of 3780 μg kg−1, and the sum of 16 priority PAHs (Σ16PAHs) varied from 347 to 17,900 μg kg−1, with a mean of 3290 μg kg−1, and the seven possible carcinogenic PAHs (Σ7CarPAHs) accounted for 36–58% of Σ16PAHs. Among different functional areas, the higher level of PAHs was found in the roadside, followed by greenbelt, commercial district, park, and residential district. The composition of PAHs was characterized by the high molecular weight PAHs, among which fluoranthene, pyrene, benzo[b]fluoranthene and chrysene were most dominant components. A correlation analysis showed that there was relatively good correlation among the individual PAHs, but the contents of PAHs were poorly correlated with soil total organic carbon (TOC). A principal component analysis and PAHs isomeric ratios indicate that PAHs in Shanghai urban soil mainly originated from combustion. The toxic assessment suggested that soil PAHs exposure is medium carcinogenic at present level.