浙东海积平原农田土壤重金属来源辨识

Distinguishing different sources of heavy metals in soils on the coastal plain of Eastern Zhejiang Province

为了区别土壤中潜在有毒重金属是来源于成土母质还是人为的污染,在浙东海积平原农田选择了32个采样点,分别采集了耕作层(0～10cm)和心土层(40～50cm)土样,用标准化学分析方法分别测定了Cd、Cu、Cr、Co、Ni、Zn、Hg、Pb、Mo、As和Al含量,用元素剖面分布研究法、元素化学形态分析法和主成分分析法等综合方法探讨了农田土壤中重金属的来源.结果表明,研究区土壤中Cr、Co、Ni为非污染元素,主要来源于成土母质,平均含量在耕作层与心土层中较为接近,残留态是这些重金属绝对优势的化学形态.Cd、Cu、Zn、Hg和Pb为主要污染元素,其耕作层含量明显高于心土层,可提取形态的比例较高;其中,Cd、Cu、Zn和Pb有相似的人为污染来源,而Hg有不同的人为污染来源.土壤中的Mo和As的变化较为复杂,可能受成土母质和外源污染双重影响.

Heavy metals may come from many different sources in agricultural soils, including relict of parent materials, fertilizer application, atmospheric deposition, vehicle emissions, industrial discharges and other activities. The origins of the metals in the soils were investigated in this work. To distinguish geogenic enrichment from anthropogenie pollution of heavy metals （ Cd, Cu, Cr, Co, Ni, Zn, Hg, Pb, Mo, and As） in agricultural soils, 32 sampling locations were selected in the coastal plain of eastern Zhejiang province. Two soil samples were collected from topsoil （0 ~ 10 cm） and subsoil （40 ~50 cm） at each location. Fractionation of elemcJ^ls ~d their speciation; profile distributions of the metals, and principal component analysis of metal concentration were used to identify the sources of the metals in the soils. The results suggest that Cr, Co, and Ni in the soils are mainly of geogenic origin, as the silicate-bound fraction was the most abundant in their speciation. Cd, Cu, Zn, Hg, Pb have a considerable contribution from anthropogenic pollution with strong topsoil enrichment. Large proportions of their extractable fractions were observed. Pollution of Cd, Cu, Zn, and Pb in the topsoil may originate from fertilizer application and atmospheric deposition, while that of Hg in the soils may originate from pesticide application and industrial discharges. Contents of Mo and As in the soils are affected by both soil parent materials and anthropogenic pollution. The results have shown that principal component analysis together with fractionation and speciation of elements and metal profile distributions can provide valuable insight into the sources of soil pollutants.