大气干湿沉降重金属元素通量及对农田土壤的影响——以四川崇州为例

    Flux of heavy metals in atmospheric dry and wet precipitation and their effects on farmland soil: A case study of Chongzhou,Sichuan

    • 摘要: 大气沉降是土壤重金属累积的重要来源。为查明四川崇州地区大气干湿沉降对农田土壤的影响,定量监测研究区干湿沉降并测试重金属含量,据此估算干湿沉降通量及重金属变化率,进行潜在生态风险评价,探讨研究区干湿沉降八项重金属元素输入在农田土壤重金属累积中的作用。研究结果表明:本区干湿沉降物重金属含量Cd、Pb、Zn超周边土壤含量,Cd、Zn超农用地土壤污染筛选值的2.25倍、1.09倍;大气干湿沉降重金属元素年通量均小于全国平均值,沉降通量Zn>Cr>Pb>Cu>Ni>As>Cd>Hg。与前人研究结果对比表明,研究区各项重金属沉降年通量均有所下降,其中Cd下降幅度最大。对于大气重金属沉降通量空间分布,除Cr元素外,其他重金属元素相对高值区基本出现在距市区、工业园区、交通干线较近,受人类活动影响较大的区域。地累积指数显示,各重金属污染程度Cd为重度—严重污染,其次为Hg、Pb,As、Ni无污染。大气干湿沉降物对土壤影响最显著的重金属为Cd和Zn,1 年后的增量分别为0.421 mg/kg、104.653 mg/kg,年变化率达到了0.138%和0.146%,表明大气沉降物为本区农田土壤中重金属Cd、Zn的重要来源之一;低沉降通量的Cd含量超标最多,引起土壤环境变化最显著,需引起注意。

       

      Abstract: It shows that atmospheric deposition is one of the main sources of soil heavy metal pollution. In order to find out the effects of atmospheric wet and dry deposition on farmland soil, the accumulation of heavy metals in farmland soil was analysed by monitoring the dry and wet deposition in the study area and testing the heavy metal content, estimating the dry and wet deposition flux, heavy metal change rate and potential ecological risk assessment. The results showed that the heavy metal content of dry and wet sediment exceeded the content of Cd, Pb and Zn in the surrounding soil, and Cd and Zn exceeded the soil pollution screening value of agricultural land by 2.25 times and 1.09 times;The annual flux of heavy metal elements in the dry and wet precipitation of the atmosphere is smaller than the national average, and the sedimentation flux order is Zn>Cr>Pb>Cu>Ni>As>Cd>Hg, the annual sedimentation flux of Zn is the highest, and the sedimentation flux of Cd is low. The geo-accumulation index showed that in the atmospheric dust, Cd reached extremely high pollution level, followed by Hg, Pb, there was no As and Ni pollution. The heavy metals with the most significant impact of atmospheric dry and wet sediment on soil were Cd and Zn, with an increase of 0.421 mg/kg and 104.653 mg/kg after one year, and the annual change rates reached 0.138% and 0.146%, which indicated that the atmospheric deposition was one of the most important sources of the heavy metal Cd and Zn in the farmland soil. The sedimentation flux of Cd is low, but its content exceeded the standard the most, and caused the most significant changes in the soil environment, which needs to be paid attention to.

       

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