2021年四川省典型重金属监管企业周边农用地土壤重金属污染特征及风险评价

Characteristics and risk assessment of heavy metal contamination in agricultural soil surrounding typical heavy metal regulatory enterprises in Sichuan province in 2021

目的强化地区排污企业监管和实施土壤污染精准管控。方法以四川省典型重金属监管企业为研究对象,于2021年7—9月采集四川省内7个行业共17家典型重金属监管企业周边83个农田土壤表层样本,分析了土壤中pH和Cu、Zn、Pb、Cd、Ni、Cr、Hg、As含量,采用污染指数法、综合潜在生态风险指数法、人体健康风险评估模型评价了土壤重金属污染特征、潜在生态风险和对企业周边人群的健康风险。结果共采集农田土样83件,土壤重金属的超标率依次为Cd(30.1%)>Zn(15.7%)>Cu(9.64%)、Pb(9.64%)、Cr(9.64%)>Hg(1.2%),不同行业超标率表现为:化学原料和化学制品制造业(75.0%)>有色金属冶炼和压延加工业(66.7%)>黑色金属冶炼和压延加工业(60.0%)>电气机械和器材制造业(50.0%)>石油、煤炭及其他燃料加工业(21.4%)>电力、热力生产和供应业(14.2%);研究区农田土壤重金属的单项污染指数依次为Cd(6.31)>Zn(1.35)>Pb(0.71)>Cu(0.65)>Cr(0.62)>Ni(0.42)>As(0.34)>Hg(0.13),各行业周边农田土壤重金属的综合污染等级为:有色金属冶炼和压延加工业(62.06)>黑色金属冶炼和压延加工业(3.61)>电气机械和器材制造业(1.91)>石油、煤炭及其他燃料加工业(1.54)>化学原料和化学制品制造业(1.49)>电力、热力生产和供应业(0.91)>生态保护和环境治理业(0.71);研究区综合潜在生态风险指数(RI)的平均贡献率表现为Cd(77.7%)>Hg(17.9%)>Pb(1.2%)>As(1.1%)>Cu(0.8%)>Ni(0.7%)>Zn(0.3%)、Cr(0.3%),不同行业综合潜在生态风险指数(RI)呈现出:有色金属冶炼和压延加工业(2532)>化学原料和化学制品制造业(535)>黑色金属冶炼和压延加工业(475)>电气机械和器材制造业(286)>石油、煤炭及其他燃料加工业(268)>生态保护和环境治理业(217)>电力、热力生产和供应业(175)的趋势;无论是成人还是儿童,土壤重金属的非致癌风险均表现为HQois(经口摄入)>HQdcs(皮肤接触)>HQpis(呼吸吸入),8种重金属对成人总的非致癌健康风险指数(HI)均小于1,4个行业(化学原料和化学制品制造业、黑色金属冶炼和压延加工业、有色金属冶炼和压延加工业、电气机械和器材制造业)儿童总的非致癌健康风险指数(HI)大于1。结论在本次研究中,研究区企业的生产活动已经对周边农田土壤造成了不同程度的重金属污染和生态风险,以Cd元素的污染水平最高、生态风险贡献最大;以有色金属冶炼和压延加工业为代表的相关企业的生产活动已经造成严重的重金属污染和极高的生态风险;研究区农田土壤重金属在3种暴露途径的综合作用下将对儿童造成较大的非致癌疾病风险,As和Cr是引起非致癌风险的主要因素,应重点预防经口摄入的暴露风险。

Objective To strengthen the supervision of regional contaminants discharge enterprises and implement precise control of soil contamination.Methods Taking typical heavy metal regulatory enterprises in Sichuan province as the research object,83 farmland soil surface samples around 17 typical heavy metal regulatory enterprises in 7 industries in Sichuan province were collected from July to September 2021.The pH and Cu,Zn,Pb,Cd,Ni,Cr,Hg and As contents in the soil were determined.The contamination characteristics,potential ecological risks and health risks were evaluated by contamination index method,comprehensive potential ecological risk index method and human health risk assessment model.Results The unqualified rate of heavy metals in farmland soil ranked as Cd(30.1%)>Zn(15.7%)>Cu(9.64%),Pb(9.64%),Cr(9.64%)>Hg(1.2%),and the unqualified rates of industries were as follows:chemical raw materials and chemical products manufacturing industry(75.0%)>non-ferrous metal smelting and rolling processing industry(66.7%)>ferrous metal smelting and rolling processing industry(60.0%)>electrical machinery and equipment manufacturing industry(50.0%)>petroleum,coal and other fuel processing industry(21.4%)>power,heat production and supply industry(14.2%).The single contamination index of heavy metals in farmland soil was Cd(6.31)>Zn(1.35)>Pb(0.71)>Cu(0.65)>Cr(0.62)>Ni(0.42)>As(0.34)>Hg(0.13),and the comprehensive contamination level of heavy metals in farmland soil around each industry was as follows:non-ferrous metal smelting and rolling processing industry(62.06)>ferrous metal smelting and rolling processing industry(3.61)>electrical machinery and equipment manufacturing industry(1.91)>petroleum,coal and other fuel processing industry(1.54)>chemical raw materials and chemical products manufacturing industry(1.49)>power and heat production and supply industry(0.91)>ecological protection and environmental governance industry(0.71).The average contribution rate of the comprehensive potential ecological risk index(RI)in the study area was Cd(77.7%)>Hg(17.9%)>Pb(1.2%)>As(1.1%)>Cu(0.8%)>Ni(0.7%)>Zn(0.3%),Cr(0.3%).The comprehensive potential ecological risk index(RI)of industries showed the following trends:non-ferrous metal smelting and rolling processing industry(2532)>chemical raw materials and chemical products manufacturing industry(535)>ferrous metal smelting and rolling processing industry(475)>electrical machinery and equipment manufacturing industry(286)>petroleum,coal and other fuel processing industry(268)>ecological protection and environmental governance industry(217)>electricity and heat production and supply industry(175).The non-carcinogenic risk of heavy metals in soil was HQois(oral intake)>HQdcs(dermal contact)>HQpis(inhalation)for both adults and children,the total non-carcinogenic health risk index(HI)of 8 heavy metals to adults was less than 1,and the total non-carcinogenic health risk index(HI)of children in 4 industries(chemical raw materials and chemical products manufacturing industry,ferrous metal smelting and rolling processing industry,non-ferrous metal smelting and rolling processing industry,electrical machinery and equipment manufacturing industry)was greater than 1.Conclusion The production activities of enterprises in the investigated area have caused different degrees of heavy metal contamination and ecological risks to the surrounding farmland soil.The contamination level of Cd element is the highest and the ecological risk contribution is the largest.The production activities of related enterprises represented by non-ferrous metal smelting and rolling processing industry have caused serious heavy metal contamination and extremely high ecological risks.Heavy metals in farmland soil in the study area will cause a greater risk of non-carcinogenic diseases to children under the combined effects of three exposure pathways.As and Cr are the main factors causing non-carcinogenic risks,and the risk of oral intake should be prevented.