• 标题：Characteristics and ecological risk assessment of polycyclic aromatic hydrocarbons in soil seepage water in karst terrains, southwest China
• 关键词：Polycyclic aromatic hydrocarbons,Karst hydrology,Soil seepage water,Dissolved organic carbon,Ecological risk assessment
• 作者：Yuchuan Suna, Siyu Zhang, Zhenglan Xie, Jiacheng Lan, Tian Li, Daoxian Yuan,Hong Yang, Baoshan Xing

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Concentrations of polycyclic aromatic hydrocarbons (PAHs) in soils and soil seepage waters were analyzed along with dissolved organic carbon (DOC) to investigate the ecological risks and factors controlling the subsurface transport of PAHs in karst terrain in southwest China. The concentrations of dissolved PAHs in soil seepage water increased with depth and the mean concentrations at a depth of 80 cm were relatively high (exceeding 1147 ng/ L). PAH composition in soil seepage water was dominated by low molecular weight (LMW) PAHs, whereas those associated with soil matrix were dominated by high molecular weight (HMW) PAHs. The results revealed that HMW PAHs in soil seepage water were closer to the equilibrium of dissolution than LMW and medium molecular weight (MMW) PAHs. However, due to the carrier functions of dissolved organic matter (DOM) for HMW PAHs, all PAHs can be continuously dissolved in the soil seepage water from soil matrix as the water moved vertical downward through the profifiles. During this process, dynamic sorption and desorption processes were occurring between constituents in the soil seepage water and the soil matrix. This study demonstrates soil seepage water has posed a high risk to the groundwater, and effffective protection is urgently needed.