Distribution and sources of polycyclic aromatic hydrocarbons in soils from Shengli Oil Field, China

Abstract

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs), which are on the United States Environmental Protection Agency (US EPA) priority pollutant list, were studied in ten different soil samples from Shengli Oil Field, China. The total PAHs concentrations in the sampled soils attained 1214.9–2965.1 ng/g (2159.6 ng/g on average). The highest total PAHs concentration was in the soil with a huge content of oil sludge, while the lowest was in fine soil environment areas. The soil contamination with PAHs in the study areas was classified as severe. The major pollutants were naphthalene, phenathrene, fluorine (Flu), pyrene (Pyr), while the detected concentration of benzo(a)pyrene (BaP), benzo(b)fluoranthene was relatively low. Among the 16 kinds of PAHs, the concentration increased in the order: 6 rings < 5 rings < 4 rings < 2 rings < 3 rings. The ratios of Flu/(Flu + Pyr) and indeno benzene(1,2,3-c,d)pyrene (IP)/(IP + BaP) were 0.46–0.48, and 0.36–0.64, respectively. Our results suggest that the main sources of PAHs were petroleum extraction and petroleum combustion. In addition, a small amount of PAHs originated from combustion of grass, woods, and coal.