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不同农业土地利用方式对土壤重金属含量影响及生态风险评价

Effects of Different Agricultural Land Use Patterns on Soil Heavy Metal Content and Ecological Risk Assessment

  • 摘要: 以撂荒地、水稻田和旱田为研究对象,分别测定其土壤As、Cd、Cu、Pb含量变化特征,结合单项污染指数法和潜在生态风险指数法,对研究区土壤进行生态风险评价,了解不同农业土地利用方式对土壤重金属污染状况及其生态风险,以期为农用地土地利用方式的选择提供参考依据。结果表明:0~50 cm土层中,土壤As含量平均值表现为旱田(26.96±11.52)mg·kg-1>水稻田(11.05±3.72)mg·kg-1>撂荒地(9.04±6.87)mg·kg-1;土壤Cd含量平均值表现为旱田(0.64±0.03)mg·kg-1>水稻田(0.44±0.18)mg·kg-1>撂荒地(0.25±0.11)mg·kg-1;土壤Cu含量平均值表现为旱田(34.11±14.83)mg·kg-1>水稻田(20.44±6.62)mg·kg-1>撂荒地(13.90±6.64)mg·kg-1;土壤Pb含量平均值表现为水稻田(39.26±9.85)mg·kg-1>旱田(38.87±7.10)mg·kg-1>撂荒地(21.94±9.68)mg·kg-1。单项污染指数分析结果表明,4种重金属在水稻田和撂荒地中均无污染,而在旱田中As和Cd为轻度污染。潜在生态风险指数分析结果表明,4种重金属单因子潜在风险指数均属于轻微生态危害,Er值为Cd>As>Cu>Pb,综合潜在生态风险指数RI均小于150,为轻微生态危害,其中以旱田土壤RI值最大,土壤重金属以Cd的贡献率最大。可见不同农业土地利用方式下,旱田对重金属的积累能力最强,水稻田次之,撂荒地最弱。农业活动虽一定程度上起到降低土壤pH的作用,但促进了土壤对重金属的积累。

     

    Abstract: Abandoned land, paddy fields and dry fields were selected as the research objects, and the change characteristics of the content of As, Cd, Cu and Pb in the soil respectively were determinded, combined with the individual pollution index method and the potential ecological risk index method, conduct ecological risk assessment on the soil in the study area, in order to understand the pollution status and ecological risks of heavy metals in the soil by different agricultural land use pattern and provide a scientific reference for the selection of agricultural land use pattern.The results showed that in the 0-50 cm soil layer, the average value of As content in the soil was as follows dry land(26.96±11.52)mg·kg-1>paddy field(11.05±3.72)mg·kg-1>abandoned land(9.04±6.87)mg·kg-1;the average value of Cd content in the soil was as follows dry land(0.64±0.03)mg·kg-1>paddy field(0.44±0.18)mg·kg-1>abandoned land(0.25±0.11)mg·kg-1;the average value of Cu content in the soil was as follows dry land(34.11±14.83)mg·kg-1>paddy field(20.44±6.62)mg·kg-1>abandoned land(13.90±6.64)mg·kg-1;the average value of Pb content in the soil was as follows paddy field(39.26±9.85)mg·kg-1>dry field(38.87±7.10)mg·kg-1>abandoned land(21.94±9.68)mg·kg-1.The results of individual pollution index analysis showed that the four heavy metals were not polluted in paddy fields and abandoned land, while As and Cd in dry fields were slightly polluted.The results of the potential ecological risk index showed that the four single-factor potential risk indexes of heavy metals were all classified as minor ecological hazards, and the order of Er value was Cd>As>Cu>Pb.The comprehensive potential ecological risk index RI was all less than 150,indicating minor ecological hazards.Among them, dry soil had the largest RI value, and soil heavy metals had the largest contribution rate of Cd.It could be seen that under different agricultural land use pattern, dry land had the strongest ability to accumulate heavy metals, followed by paddy fields, and abandoned land was the weakest.Although agricultural activities played a role in reducing soil pH to a certain extent, but they promoted the accumulation of heavy metals in the soil.

     

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