武汉市某旱地自然土壤剖面中重金属迁移规律研究

Study on the Migration of Heavy Metals in Natural Soil Profile of a Dryland in Wuhan City

以武汉市棕红壤分布地区的某旱地自然土壤剖面为研究对象,采样测定垂向上8种重金属元素(As、Cd、Cr、Cu、Hg、Ni、Pb、Zn)的含量,分析土壤剖面重金属的纵向分布和迁移特征,探讨重金属的来源。结果表明,在自然土壤剖面的酸性(pH值为5.66)环境中,Cd易于淋滤迁移,整体平均含量低于武汉市棕红壤背景值;除Cd之外,其余重金属在大部分深度中均超出背景值。迁移系数分析表明,As和Cr向下逐渐富集;Cd在表层土壤中富集,向下都是丢失趋势;Hg在表层土壤中富集,下部迁移系数变化不大;Pb的迁移系数基本都>0,有一定程度的富集;Cu、Ni和Zn迁移系数变化不大,迁移作用较弱。综合重金属含量、迁移特征以及相关性分析,认为表层土壤中Cd和Hg的含量受农业生产活动影响而明显升高;Pb含量受汽车尾气的影响而升高;其他重金属主要是自然源,基本未受人为外源影响。

Taking the natural soil profile of a dryland in the distribution area of brown red soil in Wuhan as the research object,the contents of eight heavy metals(As、Cd、Cr、Cu、Hg、Ni、Pb、Zn)in the vertical direction are measured.The vertical distribution and migration characteristics of heavy metals in the soil profile are analyzed,and the sources of heavy metals are explored.The results show that Cd is easy to leach and migrate in the acidic environment(pH 5.66)of the natural soil profile,and the overall content is lower than the background value of brown red soil in Wuhan.Except Cd,other heavy metals exceed the background value in most depths.Migration coefficient analysis shows that As and Cr are gradually enriched downward.Cd is enriched in surface soil,and there is a loss trend below it.Hg is enriched in surface soil,and the lower migration coefficient changes little.The migration coefficients of Pb are basically greater than 0,with a certain degree of enrichment.The migration coefficients of Cu,Ni and Zn change little,and the migration effect is weak.According to the comprehensive content,migration characteristics and correlation analysis,it is considered that the contents of Cd and Hg in surface soil increased significantly under the influence of agricultural production activities.The content of Pb increases due to the influence of automobile exhaust.Other heavy metals are mainly natural sources,basically not affected by man-made exogenous.