煤矸石充填复垦耕地重金属污染风险研判

Risk Assessment of Heavy Metal Pollution in Reclaimed Farmland with Coal Gangue Filling

为了研究煤矸石充填复垦耕地作物生产安全性,以辉县市程村煤矿区复垦耕地为研究对象,对复垦土壤及作物中铜(Cu)、锌(Zn)、铅(Pb)、镉(Cd)、铬(Cr)的含量进行测定,并对其污染风险进行评价。结果表明,复垦3a后,煤矸石重金属元素已经迁移到覆土层,各土层重金属元素含量均高于原覆盖土,且在土壤剖面上呈表层和深层高、中层低的分布特征。尤其是Cd元素在表层、中层和深层土壤中含量分别比原覆盖土高62.5%、50.0%、100.0%。对复垦土壤生态风险评估结果显示,以农业土壤污染风险筛选值为评价标准,单个元素的生态风险指数和综合污染指数均处于轻微风险等级;以区域土壤元素背景值为评价标准,Cd元素的生态风险指数处于中等风险等级,在表层、中层和深层土壤中的生态风险指数分别为44.90、42.55、52.35,其他重金属元素单项生态风险指数和综合生态风险指数均处于轻微风险等级。复垦耕地小麦籽粒重金属元素测定结果表明,目前生产上是安全的,其重金属元素含量的平均值、最大值均未超出粮食限量标准,但籽粒重金属含量的最小值均高于周围对照组耕地。以对照组耕地小麦籽粒重金属含量为评价标准对复垦耕地作物污染风险进行评估的结果表明,复垦耕地小麦Cd污染属中度风险等级,其他重金属元素属轻度风险等级,且各元素的综合风险指数属轻度风险等级。综上,目前复垦耕地存在一定的污染风险,需要定期对复垦土壤和作物重金属含量进行测定,并及时采取有效治理措施,以防止土壤和作物重金属含量超出限量标准。

In order to study the safety of crop production in reclaimed farmland filled with coal gangue,the reclaimed farmland in Chengcun village coal mine area,Huixian City was taken as the research object.The contents of copper(Cu),zinc(Zn),lead(Pb),cadmium(Cd),and chromium(Cr)in the reclaimed soil and crops were measured,and their pollution risks were evaluated.The results indicated that after 3 years of reclamation,heavy metal elements in coal gangue migrated to the overlying soil layer,and the content of heavy metal elements in each soil layer was higher than that of the original covering soil.The distribution characteristics of heavy metal elements in the soil profile were high in the surface and bottom layers,and low in the middle layer.Especially,the content of Cd element in the surface,middle,and deep layers of soil was 62.5%,50.0%,and 100.0%higher than that of the original cover soil,respectively.The ecological risk assessment of reclaimed soil showed that based on the pollution risk screening value of agricultural soil,the ecological risk index of a single element and comprehensive pollution index were both mild risk level.Based on the background values of regional soil elements as the evaluation criteria,the ecological risk index of Cd was a moderate risk level,with ecological risk indices of 44.90,42.55,and 52.35 in the surface,middle,and deep layers of soil,respectively.The single ecological risk index of other heavy metal elements and comprehensive ecological risk indices were all mild risk level.The determination results of heavy metal elements in wheat grains on reclaimed farmland indicated that it was currently safe in production.The average and maximum contents of heavy metal elements did not exceed the grain limit standards,but the minimum values of heavy metal content in grains were higher than those in the surrounding control group farmland.The evaluation of crop pollution risk in reclaimed farmland based on the heavy metal content of wheat grains in the control group showed that the Cd pollution belonged to a moderate risk level,while other heavy metal elements belonged to a mild risk level,and the comprehensive risk index of each element was mild risk level.In summary,there is currently a certain pollution risk in the reclaimed farmland.It is necessary to regularly measure the heavy metal content in the reclaimed soil and crops,and take effective control measures in a timely manner to prevent the heavy metal content in the soil and crops from exceeding the limit standards.