云南个旧市郊农作物重金属污染现状及健康风险

Heavy Metal Pollution in Crops Growing in Suburb of Gejiu City,Yunnan Province,China:Present Situation and Health Risk

通过现场采样及室内分析,对云南个旧市郊鸡街镇的土壤和农作物重金属污染现状进行野外调查,并进行健康风险评价。结果表明,土壤Pb、Zn、Cu和Cd含量均超出《土壤环境质量标准》(GB15618—1995)二级标准,Pb、Cu和Cd的二乙三胺五乙酸(DTPA)提取态与总量呈极显著正相关(P<0.01),Zn则呈显著正相关(P<0.05)。农作物中除萝卜、甘蓝、花椰菜和甘蔗Pb含量未超出对应的食品安全限量标准外,其余作物均超标,Pb超标率达80%,其中薄荷Pb含量最高,平均值为3.28mg.kg-(1鲜重),超标9.93倍;朝天椒、土豆、大米和玉米Cd含量均超标,Cd超标率为20%,其中大米Cd含量最高,平均值为0.446mg.kg-1,超标1.23倍;Cu和Zn在所采的农作物中均未超标。薄荷对Pb和Cu、莴苣对Zn和Cd的富集系数高于其他农作物。豌豆尖、蚕豆、甘蓝、花椰菜、葱、朝天椒、甘蔗、韭菜、厚皮菜、白菜、萝卜、青花菜、土豆和金丝菜对Pb、Zn、Cu和Cd吸收能力较低,适合在污染区继续种植;薄荷、莴苣和青菜对4种重金属吸收能力较高,不适合在污染区继续种植。根据单因子评价方法,农作物受Pb轻度、中度、重度污染分别占50%、10%和20%,受Cd轻度、中度污染各占10%。对于不同种类农作物,不同重金属的综合污染指数为Pb>Cd>Zn>Cu。居民经食用蔬菜途径日摄入Pb、Zn、Cu和Cd量分别为0.204、2.336、0.376mg.d-1和0.028mg.d-1,分别占暂定每日耐受摄入量(PTDI)的101.78%、7.08%、5.79%和39.29%。因此,经蔬菜途径摄入Pb对当地居民健康构成潜在威胁。

With the exploration,selection and smelting of mine resources,heavy metal pollution in soil is getting serious and endangers food safety and human health.A filed survey was conducted to investigate the present situation and health risk of heavy metal pollution in soils and crops in Jijie Town,located at the suburb of Gejiu City,Yunnan Province.The results indicated that average concentrations of lead（Pb）,zinc（Zn）,copper（Cu） and cadmium（Cd） in soil at the studied site exceeded ＂Environment Quality Standard for Soils＂（GB 15618—1995）（Grade Ⅱ）.A significantly positive correlation was observed between diethylenetriaminepentaacetic acid（DTPA） extractable and total concentrations of soil Pb,Cu,Cd（P0.01） and Zn（P0.05）,respectively.Concentrations of Pb in crops exceeded the maximum levels of contaminants in foods except Raphanus sativus,Brassica oleracea var.capitata,Brassica oleracea var.botrytis and Saccharum officinarum,with an exceeding rate of 80%.The highest concentration of Pb was examined in Mentha arvensis,with an average of 3.28 mg·kg-1（fresh weight）,which was 9.93 times as high as that in corresponding standard for safe food.Concentrations of Cd in Capsicu annuum,Solanum tuberosum,Oryza sativa and Zea mays also exceeded the maximum levels of contaminants in foods,with an exceeding rate of 20%.Among the examined crops,rice had the highest concentration of Cd,with an average of 0.446 mg·kg-1,which was 1.23 times as high as that in corresponding standard for safe food.However,concentrations of Cu and Zn in crops were lower than the standard for safe food.Bioconcentration factors（defined as the ratio of metal concentration in plant to that in soil） of Pb and Cu in Mentha arvensis,as well as Zn and Cd in Lactuca sativa,were higher than those in other crops.Generally,Pisum sativum,Vicia faba,B.oleracea var.capitata,B.oleracea var.botrytis,Allium fistulosum,C.annuum,S.officinarum,Allium schoenoprasum,Beta vulgaris var.cicla,Brassica rapa L.glabra Regel,R.sativus,Brassica oleracea var.italica,S.tuberosum and Brassica juncea var.multisecta were suitable for planting at study site because of their low metal accumulation,but M.arvensis,O.sativa and Brassica chinensis were not.According to the results of single-factor pollution index assessment,50%,10% and 20% of the investigated crops were polluted by Pb slightly,moderately and severely,respectively,and the remaining 20% of the crops were slightly or moderately polluted by Cd.Integrated pollution indexes of four metal elements in different crops were PbCdZnCu.Daily intake of Pb,Zn,Cu and Cd caused by consuming vegetables in residents were 0.204,2.336,0.376 mg·d-1 and 0.028 mg·d-1,accounting for 101.78%,7.08%,5.79% and 39.29% of the standard for provisional tolerated daily intake（PTDI）,respectively.Therefore,a potential threat posed to the local residents who consumed vegetables containing high concentrations of Pb.