南京沿江地区大气干湿沉降对农用地土壤重金属含量的影响

Effect of atmospheric dry and wet deposition on heavy metal content in farmland in the Nanjing section of the Yangtze River

为查明大气干湿沉降对农用地土壤环境的影响大小,通过估算干湿沉降通量、计算并分析重金属元素含量及其变化率,探讨了南京沿江地区干湿沉降中8种重金属元素输入对农田土壤重金属累积的影响。结果表明:干湿沉降物中重金属元素含量明显高于周边土壤的重金属元素为Cd,干沉降中的Cd平均含量达0.84 mg/kg,是农用地土壤污染筛选值的2.8倍;As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的年沉降通量平均值分别为12.1、1.60、89.1、47.9、0.092、46.6、36.6、116 g/(hm^(2)·a);大气干湿沉降物对土壤影响最显著的重金属元素为Cd,大气干湿沉降1年后的增量为5.33 ng/g,年变化率达1.38%,表明大气沉降物为研究区农田土壤中重金属Cd的重要来源之一。

To evaluate the effect of atmospheric dry and wet deposition on the farmland soil,accumulations of eight heavy metals in the farmland soil along the Yangtze River of Nanjing have been studied with estimation of dry and wet deposition flux and calculation of heavy metal content and change rate.Results show that the content of heavy metal Cd in the atmospheric dry and wet deposition is significantly higher than that in the surrounding soil.The average content of Cd in the dry deposition is 0.84 mg/kg,which is 2.8 times the screening value.Average annual deposition fluxes of As,Cd,Cr,Cu,Hg,Ni,Pb and Zn are 12.1,1.60,89.1,47.9,0.092,46.6,36.6 and 116 g/(hm^(2)·a),respectively.Cd is the most significant heavy metal affected by atmospheric dry and wet fallout on soil,showing an increase of 5.33 ng/g after one year of atmospheric dry and wet deposition and an annual change rate of 1.38%,indicating that atmospheric deposition is one of the important sources of heavy metal Cd in the farmland soil.