河北平原农田土壤重金属形态分布特征及控制因素研究

土壤重金属污染防治已迫在眉睫,国内外对重金属污染研究热度不减。本文选择河北平原农田为研究区,对采集325个根系土样品中的Cd、Cr、Pb、As、Hg等5种重金属进行了各形态含量统计与分析,并用Arc GIS制作了有效态空间分布图。最后运用相关性分析法探讨了5种重金属各形态与全量及pH值、Fe_2O_3、总有机碳(TOC)、阳离子交换容量(CEC)、粘粒的相关性。研究表明:Cd的有效态(水溶态和离子交换态)含量占全量比重最大,为18.06%,Cr、Pb、As、Hg均低于10%,这4种金属以残渣态为主,占全量的50%以上;As元素各形态与全量、pH值、Fe_2O_3、TOC、CEC、粘粒的相关程度最高,成正相关关系;Cr的3种形态(铁锰氧化态、强有机结合态、残渣态)与Fe_2O_3、TOC、CEC、粘粒呈显著正相关关系,Cr碳酸盐结合态、腐殖酸结合态与pH呈正相关关系,与Fe_2O_3、TOC、CEC、粘粒呈显著负相关关系;5种重金属铁锰氧化态与pH均呈正相关关系。

Speciation Distribution and Its Influencing Factors of Cd, Cr, Pb, As, Hg in Farmland Soil from Heibei Plain, China

Heavy metal pollution of soil has attracted enormous attention in recent decades. Our study area is located in farmland of Hebei Plain. A total of 325 samples were collected from root-zone soil in study area. Five kinds of heavy metals (i.e. Cd, Cr, Pb, As, Hg) were chosen to be analyzed in order to obtain the spatial distributions of their effective states using ArcGIS. Based on correlation analysis, we discussed the correlation between all speciations of five heavy metals and their total content, soil properties such as pH, Fe²O³, TOC, CEC and clay particles. Some main conclusions were drawn as follows: (1) The proportion of effective content of Cd (18.06%) is the largest, whereas the proportions of Cr, Pb, As and Hg are lower than 10%. The latter four metals are mainly in residue state, which account for more than 50% of the total content. (2) The all speciations of As show the highest positive correlation with As total content, soil pH, Fe²O³, TOC, CEC and clay. (3) Three speciations (iron manganese oxidation state, strong organic combined state, and residue state) of Cr show positive correlations with Fe²O³, TOC, CEC and clay particle. (4) The contents of Cr in carbonate combination state and humic acid binding state are positively correlated with pH, and are significantly negatively correlated with Fe²O³, TOC, CEC and clay. (5) We observe positive correlation between the content of five heavy metals in iron manganese oxidation state and soil pH.