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长期种植蔬菜土壤的重金属累积与污染风险评价

Accumulation and pollution risk of heavy metals in long-term vegetable-planted soils

  • 摘要: 以长沙城郊长期种植蔬菜的土壤为研究对象,共采集57个土壤样品,分析铅(Pb)、镉(Cd)、汞(Hg)、砷(As)、铬(Cr)等重金属的含量,对长沙主要蔬菜基地的重金属累积与污染风险进行评价。结果表明,土壤中Pb浓度为20.90-64.70 mg/kg,Cd为0.035-0.64 mg/kg,Hg为0.045-0.44 mg/kg,As为7.72-26.32 mg/kg,Cr为30.8-111.99 mg/kg。有43%的土壤样本中重金属浓度超过背景值,且Pb、Cd、Hg、As均呈现出明显的累积,尤其Cd、Hg的累积更为明显,Cd、Hg平均含量值较本底值增加了3.92倍和1.87倍,其单项污染指数超标率分别达到35.09%和24.56%(以《农产品安全质量无公害蔬菜产地环境要求GB/T 18407.1—2001》为评价标准,按照单项污染指数≥1即为超标)。分区评价结果表明,近郊区长期种植蔬菜地土壤大部分呈现轻度污染,随离市区距离的增加蔬菜地土壤重金属污染程度逐渐减弱。因此,长沙城郊长期种植蔬菜土壤的重金属污染问题需引起高度重视。

     

    Abstract: To evaluate the accumulation and pollution risk of heavy metals in the long-term vegetable-planted soils in the suburb of Changsha city, 57 soil samples in the long-term vegetable-planted fields were collected and the contents of heavy metals in the soil samples were determined. The results indicated that the contents ranges of lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), and chromium (Cr) in the soil samples were 20.90-64.70 mg/kg, 0.035-0.64 mg/kg, 0.045-0.44 mg/kg, 7.72-26.32 mg/kg, and 30.8-111.99 mg/kg, respectively. Approximate 43% of the samples exceeded the background contents of soil heavy metals in Hunan Province. Obvious accumulation of heavy metals in soils was observed, especially for Cd and Hg. That the average contents of Cd and Hg in soils were increased by 3.92 and 1.87 times as compared to their background contents, respectively. Moreover, the percentages of Cd and Hg contents in soil samples exceed the limits of GB/T 18407.1—2001 were 35.09% and 24.56%, respectively. The results of zoning evaluation of pollution risk indicated that the long-term vegetable-planted soils in suburb of Changsha city mainly occurred slight heavy metal pollution, and the heavy metals pollution reduced from the inner suburbs to the outer suburbs. Therefore, the heavy metal pollution in the long-term vegetable-planted soils should be paid more attention in the suburb of Changsha city.

     

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