江汉—洞庭交界水网平原区耕地土壤重金属污染风险评价与累积预测

Risk assessment and accumulation prediction of heavy metal pollution in cultivated land of the Jianghan-Dongting interconnected river-lake plain

  • 摘要: 耕地土壤环境污染主要表现为重金属污染.本文以Cd、Hg、As、Pb、Cr、Cu、Ni、Zn为评价因子,运用土壤环境容量理论对区域性耕地土壤重金属环境进行污染风险评价.通过核算区域内由大气沉降、化肥施用、灌溉用水和畜禽粪便还田和配合饲料投放输入的重金属量,运用动态环境容量累积规律进行累积预测.结果表明:研究区耕地土壤重金属复合污染环境风险低,环境容量较充足,除少数点位处于中高环境风险外,整体环境相对安全;单项重金属方面,As、Cd污染风险最大,部分点位存在环境污染,Hg、Pb、Cu、Zn 风险整体可控,仅少数点位处于中高风险,Cr和Ni元素风险等级最低,均为无风险或低风险;研究区耕地土壤重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn的年面积输入量分别为6.393、0.965、77.712、258.732、61.729、375.654、40.916、1 448.796 g·hm−2.未来5、10、20、30、50和100 a内,各项重金属累积量低于风险基准值,整体风险较低.未来5、10、20、30、50和100 a内累积空间分布结果表明,随着年限增加,As、Cd累积性污染风险呈逐渐加剧趋势,大气沉降、灌溉用水、畜禽粪便还田和配合饲料投放是主要输入途径.

     

    Abstract: Soil pollution of cultivated land is mainly due to heavy metal pollution. Pollution risk by heavy metals Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in regional cultivated land was evaluated in this work with soil environmental capacity. The amount of heavy metal input from atmospheric deposition, chemical fertilizer application, irrigation water, livestock and poultry manure returning to the field and compound feed in the region was calculated, accumulation prediction was carried out with accumulation law of dynamic environmental capacity. Environmental risk of compound heavy metal pollution in cultivated land in the study area was found to be low, with sufficient environmental capacity. A few points with middle and high environmental risk were identified, but overall the environment was relatively safe. For individual heavy metals, As and Cd had the greatest risk of pollution, with some points showing pollution. The risks of Hg, Pb, Cu and Zn were found to be generally controllable, with only a few points showing medium and high risks. The risk levels of Cr and Ni were found the lowest, either risk-free or of low risk. The annual input of cultivated land in the study area was as follows: Cd 6.393 g·hm−2, Hg 0.965 g·hm−2, As 77.712 g·hm−2, Pb 258.732 g·hm−2, Cr 61.729 g·hm−2, Cu 375.654 g·hm−2, Ni 40.916 g·hm−2, Zn 1448.796 g·hm−2. Predictive modeling showed that accumulated concentrations of all heavy metals over the next 5, 10, 20, 30, 50, and 100 years would remain below the risk threshold, suggesting a persistently low overall risk. Projections of spatial distribution for As and Cd accumulation over these timeframes revealed a gradual increase in pollution risk with time. Atmospheric deposition, irrigation water, livestock and poultry manure, and compound feed were identified as the primary input pathways.

     

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