北京市凉水河污灌区土壤重金属累积和形态分析

Soil heavy metal accumulation and speciation in a sewage-irrigated area along the Liangshui River, Beijing

采用野外定点连续采样和室内分析相结合的方法,对北京市凉水河污灌区土壤中Cu、Zn、Cr、Pb、Ni等重金属在土壤中的累积及其化学形态进行了系统研究。结果表明,①凉水河污灌区土壤中重金属的质量分数均高于北京地区的土壤背景值,特别是Cu和Pb分别达到北京市土壤环境背景值的3.47倍和4.53倍,凉水河污灌区土壤已经发生明显的重金属累积。②土壤重金属元素之间相关分析表明研究地区存在重金属复合污染,土壤有机质与土壤重金属显著相关表明污灌可能是导致土壤重金属富集的重要原因;土壤各理化性质与土壤重金属相关性表现不一致,土壤重金属富集与迁移的影响因素复杂多样。③Tessier连续提取法测定土壤5种重金属的形态分布规律均为:残渣态>铁锰结合态>有机结合态>碳酸盐结合态>可交换态,铁锰结合态含量较高与污水中铁锰含量较高具有一定的关系;凉水河污灌区重金属潜在迁移能力顺序为:Cu>Zn>Pb>Ni>Cr。④综合分析各土壤重金属富集状况、形态分布及其生态毒性,Cu和Pb是凉水河污灌区土壤中需要优先控制的重金属。

Soil samples were collected in a sewage-irrigated area along the Liangshui River of Beijing to study the pollution degree and speciation of heavy metals. Total concentrations of Cu, Zn, Cr, Pb and Ni were determined, and their chemical fractions were partitioned with a sequential extraction procedure. Results showed that heavy metals were heavily accumulated in soils, with total Cu and Pb 3.47 and 4.53 times as much as the environmental background values of Beijing, respectively. The significant positive correlations between some pairs of heavy metals except for Ni may indicate compound pollution of heavy metals which came from the same pollution sources with sewage irrigation. Most heavy metals had a very significant negative correlation with soil pH, and very significant positive correlations with organic matter, total nitrogen, available P and electrical conductivity. Sequential extraction of heavy metals showed that the distribution of Cu, Zn, Cr, Pb and Ni had a similar trend of residual〉oxidizable〉reducible〉acid solu- ble〉exchangeable, and higher percentage of oxidizable fraction was in accord with the higher Fe and Mn concentrations in the sewage. With the sum of the latter 3 fractions as the potential mobility, the mobility of soil heavy metals were in the order ofCu 〉Zn 〉Pb 〉 Ni〉 Cr, and Cu and Pb were the priority metals to be controlled.