模拟氮沉降对三峡库区消落带土壤重金属的活化研究

Study on the Activation of Heavy Metals in the Soil of the Water Level Fluctuation Zone of the Three Gorges Reservoir by Simulated Nitrogen Deposition

以三峡库区万州谭绍村消落带土壤为研究对象,利用原状土柱淋溶实验,通过设置不同氮添加量(0 kgN/(hayr)、20 kgN/(hayr)、40 kgN/(hayr)和60 kgN/(hayr))模拟研究了氮沉降对土壤As、Cd、Cr、Cu、Ni、Pb、Zn的活化过程的影响。研究结果表明:(1)随着氮添加量的增加,土壤pH值呈下降变化趋势,土壤酸化程度显著增加。(2)重金属向环境中迁移累积释放量与淋溶时间呈正相关关系。土壤中的重金属的迁移主要依靠降水的动力作用向环境水体中迁移。(3)氮素的添加会导致土壤重金属向毒性高的活性离子形态转化,会导致消落带土壤-水体环境风险增大,加大了对土壤环境,水环境的重金属污染的危害。其中,在40 kgN/(hayr)添加条件下,活化率最高,约为359%~2116%。

Taking the soil which in the water-fluctuating zone of Tanshao village in Wanzhou,Three Gorges Reservoir Area as the research object,leaching experiment using undisturbed soil columns,simulation by setting different nitrogen additions(0 kgN/(ha yr),20 kgN/(ha yr),40 kgN/(ha yr)and 60 kgN/(ha yr)).The effects of nitrogen deposition on the activation processes of the Water level Fluctuation Zone of the Three Gorges Reservoir soil As,Cd,Cr,Cu,Ni,Pb,and Zn.The result shows:(1)With the increase of nitrogen addition,the pH value of the soil showed a downward trend,and the degree of soil acidification increased obviously.(2)Cumulative release of heavy metals into the environment has a positive correlation with leaching time.The migration of heavy metals in soil mainly depends on the dynamic effect of precipitation to migrate to environmental water bodies;(3)Nitrogen deposition will cause the transformation of soil heavy metals into highly toxic active ions,which will increase the risk of soil-water environment in the drawdown zone,and increase the harm of heavy metal pollution to soil environment and water environment.Among them,the activation rate was the highest under the condition of 40 kgN/(ha yr),about 359%~2116%.