土法炼锌导致土壤中铅分布特征和形态变化的研究

对贵州省赫章县土法炼锌区土壤中Pb分布特征和形态变化进行了研究。各炼锌点表层土壤中全铅含量71.8~37247.4 mg.kg-1,远高于贵州省土壤背景值(29.3 mg.kg-1)。其分布特征表现为:土壤中Pb含量总趋势随着炼锌时间增加而增加,随着距废渣堆的距离增加而降低。剖面中全铅含量分析表明Pb主要累积在土壤表层,但随着冶炼时间增加深层土壤中Pb累积程度也逐渐加大。以CaCl2和DTPA作为提取剂的简化连续提取法对土壤中Pb形态进行分析,结果显示,土壤中CaCl2和DTPA提取态Pb占全量的比例很低,平均值分别为0.3%和5%,但是其绝对含量高达6.4~1037 mg.kg-1;并随着Pb在土壤中累积时间的加长,CaCl2和DTPA提取态Pb所占比例呈显著降低的趋势,但其绝对含量逐渐增加。

THE DISTRIBUTION CHARACIERS AND CHEMICAL SPECIATION VARIATIONS OF LEAD IN THE SOIL INDUCED BY LOCAL ZINC SMELTING ACTIVITIES IN HEZHANG COUNTY,GUIZHOU PROVINCE

The contamination of lead in soil induced by local zinc smelting activities in Hezhang County,Guizhou Province was studied.The total lead amount in adjacent soil ranges from 71.8～37247.4 mg/kg,and tends to increase with the smelting history.Generally,contamination level of Pb decreased with distance from the smelting area,though this trend differs somewhat in different smelting areas.The vertical distribution of Pb in the soil profile showed that lead was mainly concentrated in top soil(0-20 cm),however,in deep layer soil(20-50 cm) lead also increased to some extent and the Pb content of subsoil increased with the smelting history.In addition,the chemical fractions of Pb were extracted by 0.01 mol·L-1 CaCl2 and 0.005 mol·L-1 DTPA,and the results showed that the CaCl2 extractable and DTPA extractable fractions were very low in percentage(0.3%,5%)of the total content,but its contents are up to 6.4～1037 mg/kg,and tend to increase with increasing accumulated time of Pb in the soil,but their percentages decreased with increasing accumulated time of Pb in the soil.