基于TCLP法的钼矿区周边农田土壤重金属风险评价

Risk Assessment Based on TCLP Extrated Heavy Metals in Soil at Farmlands Near Molybdenum Mining Area

【目的】明确福建省某钼矿区周边农田土壤重金属和钼含量及其风险,为钼矿区周边土壤的安全利用提供依据。【方法】于2018年8月在钼矿区周边采集10个表层(0~20cm)土壤样品,测定了Cd、Pb、Zn、Cr、Ni、Cu和Mo等7种元素的全量和TCLP(Toxicity characteristic leaching procedure)提取量,并基于此进行了评价。【结果】调查区域7种重金属元素含量均大于福建省土壤环境背景值的规定,10个采样点土壤Cd、Zn和Cu含量均超过农用地土壤污染风险筛选值的规定,Mo的含量均大于安全阈值规定,超标率达100%。基于TCLP法评价的钼矿区土壤重金属存在的风险主要是由Cd、Pb和Mo元素引起的。采用内梅罗综合污染指数评价结果表明,调查区域土壤处于轻度污染以上等级的达到60%,随着离矿口距离的增加,污染程度越低。【结论】钼矿区周边土壤存在一定的重金属污染,TCLP提取的Cd、Pb和Mo存在较高的风险,离矿口越近的土壤污染风险越严重。

【Objective】Heavy metals and molybdenum(Mo)in the soil at farmlands around a Mo-mining area in Fujian were determined to assess the environmental pollution and health risk.【Method】Soil samples at depth of 0-20 cm were collected for analysis at the farms close to a Mo-mine in August 2018.The total,as well as the TCLP(Toxicity Characteristic Leaching Procedure)extracted,Cd,Pb,Zn,Cr,Ni,Cu and Mo were determined for the assessment.【Result】All of the Cd,Cu,Cr,Ni,Pb,Zn and Mo contents in the soil samples exceeded the provincial environmental limits.The total Cd,Zn and Cu contents in soil at 10 of the sampling lots exceeded the thresholds for agricultural land use,according to the Environmental Quality Standard for Soil.The Mo contents at all sites were higher than the safety limit.Data on the TCLP-extracted Cd,Pb and Mo indicated that these elements were of major risk concerns.The Nemerow comprehensive pollution index on soil showed that 60%of the sites were moderately polluted and that the farther away from the mine,the lower the degree of contamination of the land.【Conclusion】Pollution by heavy metals in the soil was evident at the surveyed areas.Relatively,Cd,Pb and Mo posed a greater health risk than other heavy metals for the farmlands nearby the Mo-mine.The soil pollution tended to be more severe at the farms closer to the mine.