广西某铅锌矿影响区农田土壤重金属污染特征及修复策略

为了解铅锌矿影响区农田土壤重金属分布特征及探究污染农田的修复措施,以广西某铅锌矿影响区为研究对象,分别采集影响区自然土壤和农田耕作层土壤样品41个和277个,同时分别采集62个蔬菜和35个粮食样品,分析重金属含量。结果表明,铅锌矿影响区耕作层土壤As、Cd、Pb、Cu、Zn和Cr含量范围分别为4.50~104.8、0.031~36.26、24.80~2989、16.90~251.6、79.90~11 500和24.0~222.0 mg·kg~(-1);与土壤基线值相比,6种重金属的超标率分别为1.4%、91.7%、60%、60%、60%和0。与《食品中污染物限量》(GB 2762—2017)中限值相比,大米样本As、Pb、Cd含量超标率分别为93%、86%、64%,玉米样本Pb、Cd含量超标率为100%、100%,叶菜类蔬菜As、Pb、Cd含量超标率分别为50%、100%、60%,根茎类蔬菜As、Pb、Cd含量超标率为23%、100%和100%,瓜果类蔬菜As、Pb、Cd含量超标率为14%、96%和100%。通过分析土壤和农产品重金属超标情况,确定As、Pb、Cd为优先控制的重金属,依据研究区土壤重金属污染空间分布特性,划为3个分区:轻度污染区(Cd污染区),建议采取活化剂+植物萃取去除污染物;中度污染区则采用钝化剂与低积累农作物结合的方式;重度污染区则不宜种植进入食物链的农作物,建议采取施加活化剂与种植超富集植物结合的方式降低土壤重金属含量。

Characteristics and remediation strategy of heavy-metal polluted agricultural soil near a lead and zinc mine in Guangxi

The aim of this study was to investigate the distribution characteristics of heavy metals in farmland areas affected by a lead-zinc mine and to explore remediation measures of polluted farmland. Heavy metal concentrations were surveyed using 41 background soil and 277 agricultural soil samples as well as 62 vegetable and 35 food samples collected near a lead-zinc mine in Guangxi Province. The results showed that the concentrations of heavy metals in soils were 4.500~104.8(As), 0.031~36.26(Cd), 24.80~2989(Pb), 16.90~251.6(Cu), 79.90~11 500(Zn), and 24.00~222.0(Cr) mg·kg^-1, which exceeded the baseline values of the six heavy metals by 1.4%, 91.7%, 60%, 60%, 60%, and 0, respectively. The concentrations of As, Pb, and Cd in rice, and Pb and Cd in maize exceeded the Maximum Levels of Contaminants in Foods(MLC, GB 2762-2017) by 93%, 86%, 64%, 100%, and 100%, respectively. As, Pb, and Cd, exceeded the MLC by 50%, 100%, and 60% in leaf vegetables, 23%, 100%, and 100% in root vegetables, 23%, 100%, and 100% in root/stem vegetables, and 14%, 96%, and 100% in fruit vegetables, respectively. As, Pb, and Cd are thus the priority heavy metals for treatment. According to the spatial distribution characteristics of the surveyed heavy-metal pollutants in the area, three remediation strategies are recommended. In areas lightly polluted by Cd, the use of an activator and plant extracts to remove pollutants is recommended. In moderately polluted areas, the combination of a passivator with low-accumulating crops is recommended. In heavily polluted areas, the combination of an activator with hyperaccumulation plants is suggested, and main food crops should be avoided.