酸雨淋溶条件下赤泥中重金属在土壤中的迁移特性及其潜在危害

为探讨在气候特征较特殊区域的赤泥堆场溃坝后,赤泥中重金属对土壤及地下水的影响,以我国普遍存在的联合法赤泥为研究对象开展土柱模拟实验。结果表明:赤泥经酸雨淋溶后,溶出的As、Cr、Cd、V、Mo 5种重金属主要累积在表层(0~20 cm)土壤中,平均浓度分别达到17.71、42.31、0.79、57.77、29.76 mg·kg-1,与原始浓度相比分别增加了5.83、1.36、2.21、2.34、1.89倍;Pb与Zn在0~60 cm深度土壤累积明显,平均浓度分别达到18.67、58.52 mg·kg-1,分别增加了8.76、3.86倍,Cu、Ni在土壤中含量有微量增加,累积现象不明显;赤泥经酸雨淋溶后,As、Ni酸可提取态平均占比较高,可迁移性强,Cu、Cr、Mo主要以可氧化态和可还原态存在,Pb、Zn、V主要以可还原态存在,具有较大的潜在迁移性;渗滤液中仅检出较低浓度的Mo、V、Pb、Cu,说明赤泥经酸雨淋溶后,溶出的重金属主要滞留在土壤中,对土壤造成较大的潜在危害。

Migration characteristics and potential hazards of heavy metals from bauxite residue to soil under simulated acid rain

To understand the influence of heavy metals from combined bauxite residue on soil and groundwater, the migration characteristics of which were investigated using soil column experiments. Results showed that dissolved As, Cr, Cd, V, Mo accumulated mainly in the surface layer(0~20 cm) soil with the average concentration 17.71, 42.31, 0.79, 57.77, 29.76 mg·kg^-1, respectively after leaching with acid rain(compared with the original concentration, increased by 5.83, 1.36, 2.21, 2.34, 1.89 times, respectively). Pb and Zn accumulated significantly in the 0~60 cm depth soil with the average concentration 18.67 mg·kg^-1 and 58.52 mg·kg^-1(8.76 times and 3.86 times, respectively). And Cu, Ni accumulated insignificantly in soil. Considering the heavy metal chemical speciation, As, Ni indicated greater migration risk for the highly acidic soluble fraction in soil. Cu, Cr, Mo in soil were mainly associated with oxidizable fraction and reducible fraction, and Pb, Zn, V were mainly reducible fraction, indicating higher potential mobility. Mo, V, Pb, Cu only detected in lower concentrations in the leachate, which ellucidating that the dissolved heavy metals mainly retained in soil.