长期污灌条件下农田土壤重金属污染环境风险评价

    Environmental Risk Assessment of Soil Heavy Metal Pollution of Farmlands With Long Period of Sewage Irrigation

    • 摘要: 为探讨长期污灌条件下农田土壤重金属积累状况及环境风险,选取典型污灌河流汪洋沟沿岸农田作为研究对象,对污灌区土壤和小麦植株中重金属Cd、Pb、Cu和Zn含量进行分析,并对重金属污染现状、潜在生态风险和潜在健康风险进行评价。结果表明,污灌土壤中Cd、Pb、Cu、和Zn含量虽未超过国家标准限值,但均高于清灌土壤和土壤背景值,已表现出积累现象。污灌小麦部分样本Pb和Zn含量超标,超标率分别为23.1%和15.4%。Cd、Pb、Cu和Zn 4种重金属污染等级均为安全,说明重金属含量尚未达到警戒水平。潜在生态风险评价结果显示,Cd的生态危害系数最高,表现出中等生态危害程度;Pb、Cu和Zn表现为轻微潜在生态危害。健康风险评价显示,4种重金属的单一健康风险系数均未达到显著水平,但其综合污染风险指数大于1,说明该地区存在一定的潜在健康风险,且重金属对儿童的健康风险大于成人,应引起足够重视。

       

      Abstract: To investigate soil accumulation of heavy metals in farmlands that have long been irrigated with sewage and its environmental risks,samples of the soil and wheat plants were collected from typical sewage irrigated farmlands alongside the Wangyanggou,a typical sewage irrigation river,for analysis of Cd,Pb,Cu and Zn contents,and status quo of the heavy metal pollution,potential ecological risks and potential health risks were evaluated. Results show that although the contents of Cd,Pb,Cu,and Zn did not exceed the limits set in the national standard,they were higher than the soil background values and those in the soil irrigated with clean water,indicating that heavy metal accumulation had already started. In about 23. 1% and 15. 4% of the wheat plant samples,the contents of Pb and Zn were higher than the standards.However,the contaminations of Cd,Pb,Cu and Zn were still in the safe range,indicating that the heavy metal contents had not yet reached their respective alarming levels. Potential ecological risk assessment shows that Cd was the highest in ecological risk coefficient,posing a moderate ecological hazard; and Pb,Cu and Zn posed slight potential ecological risks.Health risk assessment shows that none of the four heavy metals reached a significant level in single-factor health risk coefficient,but their integrated pollution risk index was higher than 1,indicating that there are certain potential health risks in this region,which are more hazardous to children than to adults. Therefore,the situation calls for adequate attention.

       

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