气型污染农田土壤中重金属含量及潜在生态风险评价*
Pollution and potential ecological risk assessment of heavy metals in agricultural soils of gas-type pollution

目的:评价河南某工厂附近由于工业废气沉降引起的农田土壤重金属污染状况及潜在生态风险。方法:于该工厂西侧(该地常年主导风向下风侧),依次选择距离741～2 556 m的7块农田观察区(G1～G7),分4个季节采集混合土样,测定土壤中汞、砷、铅、镉、铜、锌、镍、铬8种重金属含量。单项累积指数法和内梅罗指数法进行重金属累积性评价,Hakanson潜在生态危害指数法进行土壤生态风险评价。结果:28份农田混合土样中镉、铅含量分别超过土壤环境质量二级标准6.08和0.07倍。G1和G2观察区6种重金属含量均高于其他较远距离的各观察区,G3观察区的砷、汞、铜和锌含量高于G6、G7观察区含量(P＜0.05)。镉、铅、汞的单项累积指数范围在8.15～342.69之间,达到重度累积。G1～G7观察区的综合累积指数为731.13～30 588.88,均达到重度累积; G1～G7观察区的总潜在生态危害指数范围为1 620.29～14 659.37,均达到极强生态危害。结论:该气型污染农田土壤中镉、铅、汞污染达到重度累积,存在极强生态危害。
Aim: To evaluate the pollution and potential ecological risk of heavy metals caused by industrial waste gas deposition of agricultural soils near a factory in Henan.Methods: Seven agricultural observation areas(G1-G7)were selected among different distances from 741 to 2 556 m on the west side of the factory(the area perennial dominant wind direction leeward), and twenty-eight mixed soil samples were collected in four seasons. The concentrations of heavy metals in agricultural soils(Hg, As, Pb, Cd, Cu, Zn, Ni, and Cr)were detected. Single cumulative index method, Nemerow index method and Hakanson potential ecological risk index method were used to assess the accumulation of heavy metals and potential ecological risk of the farmland.Results: Contents of seven kinds of heavy metals except for Cr in 28 soil samples exceeded the corresponding background values in Henan Province, also, the mean contents of Cd and Pb compared with Soil Environmental Quality Standard were 6.08 and 0.07 times, respectively. Contents of six kinds of heavy metals except for Cr and Ni in observation area G1 and G2 were higher than other observation areas, and the concentrations of As, Hg, Cu, and Zn in G3 area were higher than those in G6 and G7 areas(P＜0.05). Single cumulative indexes of Cd, Pb and Hg ranged from 8.15 to 342.69, and reached up to most severe level. Nemerow indexes of seven different observation areas were also most severe(between 731.13 and 30 588.88). The total potential ecological risk(1 620.29-14 659.37)of seven observation areas was extremely severe.Conclusion: The concentrations of Cd, Pb, and Hg in gas-type polluted agricultural soils reach up to severe accumulation and have an extremely severe ecological risk