模拟酸雨作用下红壤中多环芳烃的释放及纵向迁移特征

Release and Vertical Migration of Polycyclic Aromatic Hydrocarbons in Red Soil Under Simulated Acid Rain

以USEPA优先控制的16种多环芳烃为研究对象,通过酸雨的土柱淋溶试验模拟实际降水过程,分析了不同酸度的模拟酸雨淋溶后红壤中多环芳烃残留量的变化及不同性质多环芳烃在土柱中纵向迁移特征。研究结果表明:不同酸度模拟酸雨淋溶后红壤中多环芳烃残留量均较淋溶前减少,pH2.5酸雨淋溶后红壤中多环芳烃含量较淋溶前减小的幅度最大(52.08%),pH5.6酸雨淋溶后减小的幅度最小(21.55%);酸雨破坏土壤微结构,使土壤胶体分散,粘粒下移,与土壤粘粒结合在一起的多环芳烃也一起向下迁移,酸雨pH值越小,多环芳烃在土壤中的纵向迁移能力就越强;酸雨对土壤中不同性质多环芳烃的纵向迁移影响不同,对低环多环芳烃(环数≤4)的迁移影响较大,对高环多环芳烃(环数>4)影响较小,主要是由于不同性质多环芳烃在土壤中结合的物质不同而引起的。该研究结果为了解酸雨作用下多环芳烃在土壤介质中的稳定性及其对地下水潜在污染的风险评价提供理论依据。

Polycyclic aromatic hydrocarbons（PAHs）have accumulated in many soils. Acid rain may influence their environmental behaviors and ecological effects. This study investigated the impacts of simulated acid rain on release and vertical migration characteristics of USEPA’s 16 priority PAHs in red soil columns leached by simulated acid rain in a laboratory experiment. The pH values of the simulated acid rain ranged from 2.5 to 5.6. Leaching with simulated acid rain significantly decreased residues of PAHs in soils. The decline in residual PAHs was the greatest（52.08%）at pH2.5, whereas the least（21.55%）at pH 5.6. Acid rain promoted the vertical migration of PAHs in the soil profile, might due to enhanced concurrent downward migration of soil clay and PAHs resulted from destructed soil microstructures and dispersed soil colloids caused by acid rain. Acid rain had greater effects on the migration of low ring PAHs（ring number≤4）than that of high ring PAHs（ring number〉4）. That is because PAHs with different rings are associated to different soil components. These results would advance our understanding of stability and groundwater pollution risk assessment of PAHs in soils under acid rain.