Distributions and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils around a Chemical Plant in Shanxi, China

Background: Yearly the Shanxi coal chemical industry extracts many coal resources, producing at the same time many polycyclic aromatic hydrocarbons (PAHs) that are emitted as by-products of coal incomplete combustion. Methods: Sixty-six soil samples collected from 0 to 100 cm vertical sections of three different agricultural (AS), roadside (RS) and park (PS) functional soils around a chemical plant in Shanxi, China were analyzed for the presence of the 16 priority control PAHs. Results: The total concentrations (∑16PAHs) varied in a range of 35.4-116 mg/kg, 5.93-66.5 mg/kg and 3.87-76.0 mg/kg for the RS, PS and AS surface soil, respectively, and 5-ring PAHs were found to be dominant (44.4-49.0%), followed by 4-ring PAHs (15.9-24.5%). Moreover, the average value of ∑16PAHs decreased with the depth, 7.87 mg/kg (0-25 cm), 4.29 mg/kg (25-50 cm), 3.00 mg/kg (50-75 cm), 2.64 mg/kg (75-100 cm) respectively, in PS and AS soil vertical sections. Conclusions: The PAH levels in the studied soils were the serious contamination level (over 1.00 mg/kg) according to the Soils Quality Guidelines. The carcinogenic PAHs (ΣBPAHsBapeq) were approximately 14.8 times higher than the standard guideline level (0.60 mg/kg) and 90.3% of PAHs were produced by coal/wood/grass combustion processes.