于2008年秋季,在第二松花江(二松)下游的前郭灌区内,采集具有不同灌溉史水田的水稻籽粒样品23个,测定稻米和稻壳中Hg, Cd,Cu, Zn, Ni和Cr的含量,讨论了重金属累积特征,并分别采用单项污染指数法和内梅罗综合污染指数法对稻米重金属含量水平进行了风险评价.结果表明,灌溉史越长的水田稻米中Hg含量越高,而稻米中Cd, Cu, Zn, Ni和Cr的含量与水田灌溉史的关系不明显一稻米与稻壳中重金属含量顺序基本一致.Zn在稻米中的含量高于稻壳,其余重金属在稻壳中的含量高于稻米单项污染指数法评价结果显示仅有1例稻米样品Ni含量超过国家标准含量限值.稻米样品重金属内梅罗综合污染指数为0.330.91,平均值为0.51,总体处于安全级水平.通过对稻米重金属的研究发现,长期提取二松江水灌溉导致水田稻米中Hg出现累积,但其累积水平很低,未构成生态风险.以二松为主要水源的哈达山水库建成后,通过灌溉对当地粮食安全造成的影响也较低.%A total of 23 rice grain samples were collected from paddy fields with different irrigation histories in Qianguo Irrigation Area, which is located in the downstream of the Second Songhua River basin, in the fall of 2008.Concentrations of Hg, Cd, Cu, Zn, Ni and Cr in rice flesh and hulls were determined and risks were assessed based on relative national standards of China. The concentrations of Hg in rice flesh increased with irrigation histories of the paddy fields while no significant relationships were found between the other metal elements and irrigation histories. The heavy metal concentrations in rice flesh and hulls from paddy fields with different irrigation histories took similar orders. The concentrations of Zn in rice flesh were higher than in rice hulls while the concentrations of Cd, Cu, Cr, Hg, and Ni were opposite. Using the monomial pollution index method, only one rice flesh sample was detected with higher Ni than the nationar standard. The composite pollution indexes of rice flesh ranged from 0.33 to 0.91, with the average of 0.51, which was considered to be in the level of security. The results show that the historical pollution of the Second Songhua River resulted in the bioaccumulation of Hg in dee flesh, but it has not posed ecological risks. Consequently, after the Hadashan Reservoir depending on the Second Songhua River as water source is built, the irrigation will pose low ecological risks to the food security in this area.
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