Distribution characteristics and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in underground coal mining environment of Xuzhou

Polycyclic aromatic hydrocarbons (PAHs) in underground mining environment pose serious threats to groundwater and surface ecological environment with the migration and flow of mine water. We collected 26 underground samples from six mines of Xuzhou, including coal, mine water, and underground sludge, to measure the 16 PAHs, aiming to investigate the contamination level, distribution, and possible sources and to estimate the ecological risks of PAHs. Results showed that the concentrations of 16-PAHs (mean value) in the coal, mine water, and underground sludge were 15.87 μg/g, 0.82 μg/L, and 10.63 μg/g, respectively. There was a significant difference in the number of rings between different coals, and 2-3 ring PAHs occupied the majority of PAHs in mine water, which was determined by the Kow of PAHs. Coal and underground sludge contained more carcinogenic PAHs than mine water. And the main carcinogenic PAHs in coal were BaA, BbF, and InP, and for underground sludge were BbF, CHr, and BaP. Risk quotient (RQ) was used to evaluate the ecological risk of mine drainage, showing that PAHs in mine water were generally at medium-high risk levels. This study highlights the PAHs pollution problems in underground mining environment, particularly the potential ecological risks of mine drainage in Xuzhou.