模拟酸雨对泉州市交通区表层土壤重金属淋溶的累积释放特征

用模拟酸雨动态淋溶试验方法和改进的BCR四步提取法研究泉州市交通繁忙区表层土壤中重金属的溶出规律及形态变化,用ICP-AES测定浸出液中Ti、Zn、Co、Ni、V、Fe、Mn、Cr、Cu、Pb、Cd和As的含量。结果表明大部分重金属元素(Mn、Fe、Ni、Cu、Zn、Pb)累积释放量随模拟酸雨pH值的降低而增加。对土壤中金属释放过程进行数学方程拟合后发现,应用双常数速率方程能更好地描述V、Co和Ni的释放规律,抛物线方程则能更好地描述Zn的释放过程,修正Elovich方程能更好地描述Ti、Cr、Mn、Fe、Cu和Pb的释放过程,而双常数速率方程和抛物线方程均能很好地描述As、Cd的释放过程。对比淋溶前后重金属形态分布,发现淋溶后土壤中Ti、Cr、Mn、Fe、Co、Ni、Cu、Zn、Pb的生物有效态比例有所增加,而V、Cd和As的生物有效态比例略有降低。

Release Characteristics of Heavy Metals in the Traffic-Area Topsoil Leached by Simulated Acid Rain

The release characteristics of heavy metals in the topsoil, collected from a heavy traffic area in Quanzhou City, were investigated by dynamic leaching experiment with simulated acid rain. The speciation of heavy metals in the topsoil, before and after having been leached by the simulated acid rain, was also studied by using the modified BCR-sequential extraction technique. The concentrations of Ti, Zn, Co, Ni, V, Fe, Mn, Cr, Cu, Pb, Cd and As were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results showed that the total release contents of most studied heavy metals (Mn, Fe, Ni, Cu, Zn, Pb) increased significantly with decreasing pH value of the simulated acid rain. The release processes of metals from soil were fitted with mathematical equations. The double constant velocity equation could better describe the release processes of V, Co and Ni, the parabola equation could better describe the release process of Zn, and the amended Elovich equation could better describe the release processes of Ti, Cr, Mn, Fe, Cu and Pb. Both the double constant velocity equation and parabola equation could better describe the release processes of As and Cd. After having been leached by the simulated acid rain, the bioavailable proportions of Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb increased, while those of V, Cd and As slightly decreased.