Polycyclic aromatic hydrocarbons in the soil profiles (0–100 cm) from the industrial district of a large open-pit coal mine, China

Abstract

Mining and industrial activities are the primary sources of soil pollution in the open-pit coal mine. The concentrations of PAHs in 11 sampling sites in the industrial district and 9 sampling sites with different land use types in Pingshuo open-pit coal mine, China, were measured to investigate the distributions of PAHs and possible sources in soil profiles (0–100 cm). In the topsoil layer (0–20 cm), concentrations of 16 PAHs ranged from 2.15 to 33.51 mg kg⁻¹, with a mean value of 11.93 mg kg⁻¹. PAHs were more variable in the middle soil layer (20–50 cm), ranging from 0.199 to 36.888 mg kg⁻¹ with the average value of 9.21 mg kg⁻¹. Comparable extreme concentrations were detected from the samples in the subsoil layer (50–100 cm). Compared with those in topsoil, the average concentrations of the most individual PAH species were less in the middle soil and subsoil layers. The concentrations of most of the individual PAHs in the topsoil were higher than those in the middle soil and subsoil. Distribution patterns of PAHs in the three soil layers correlated well with each other. The high concentration hotspots were concentrated around the old coal washery, reaching about 30 mg kg⁻¹. The average concentrations of PAHs with different rings in the industrial district exceeded those in the other land use types. However, only the concentrations of 5-ring PAHs in topsoil showed difference with different land use types (P < 0.05). Diagnostic ratios and the total index showed that petroleum combustion was the main source of PAHs.