Identification of sources of elevated concentrations of polycyclic aromatic hydrocarbons in an industrial area in Tianjin, China

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography equipped with a mass spectrometry detector in 105 topsoil samples from an industrial area around Bohai Bay, Tianjin in the North of China. Results demonstrated that concentrations of PAHs in 104 soil samples from this area ranged from 68.7 to 5,590 ng g − 1 dry weight with a mean of ∑16PAHs 814 ± 813 ng g − 1, which suggests that there exists mid to high levels of PAH contamination. The concentration of ∑16PAHs in one soil sample from Tianjin Port was exceptionally high (48,700 ng g − 1). Ninety-three of the 105 soil samples were considered to be contaminated with PAHs (>200 ng g − 1), and 25 were heavily polluted (>1,000 ng g − 1). The sites with high PAHs concentration are mainly distributed around chemical industry parks and near highways. Two low molecular weight PAHs, naphthalene and phenanthrene, were the dominant components in the soil samples, which accounted for 22.1% and 10.7% of the ∑16PAHs concentration, respectively. According to the observed molecular indices, house heating in winter, straw stalk combustion in open areas after harvest, and petroleum input were common sources of PAHs in this area, while factory discharge and vehicle exhaust were the major sources around chemical industrial parks and near highways. Biological processes were probably another main source of low molecular weight PAHs.