石家庄农田区土壤重金属Cd、Cr、Pb、As、Hg形态分布特征及其影响因素

土壤重金属污染是国内外亟待解决的环境问题。随着重金属元素迁移和转化的深入研究,重金属的毒性不仅与其全量有关,而且在更大程度上受形态分布所控制。本文选择石家庄农田区为研究区,采集了31个根系土样品,对土壤中的Cd、Cr、Pb、As、Hg等5种重金属进行了形态分析,并探讨了影响重金属化学形态的影响因素。研究表明:Cd的有效态含量占全量比重最大,40.94%,其次是Pb的12.73%,Cr、Pb、As、Hg均以残渣态为主;5种重金属各形态和全量的相关程度较高,尤其是Pb;土壤pH值与Cd、Cr、Pb元素碳酸盐结合态、强有机结合态和腐植酸结合态均呈显著负相关关系,受pH值的影响顺序为:CrPbCd;各重金属元素的残渣态含量与Fe2O3含量均呈显著的正相关关系;5种重金属的离子交换态与TOC均呈负相关关系;CEC和重金属元素的水溶态和残渣态均呈正相关关系;粘粒的含量与Cr的离子交换态呈显著负相关关系,与各元素残渣态呈正相关关系。

Form Distribution Characteristics and Influencing Factors of Cd, Cr, Pb, As and Hg in Farmland Soil from the Shijiazhuang Area, China

Soil pollution by heavy metals has been an environmental problem all over the world. With deep-going research on the transport and transform of heavy metal elements, metal toxicity was recognized to be not only related to the total amount of metals, but also mostly depend on their chemical forms. In this paper, the authors took the farmland area in Shijiazhuang City, Hebei Province, as a study area to investigate the chemical forms of soil heavy metals (Cd, Cr, Pb, As, Hg) and their influencing factors in 31 root soil samples analyzed. The results showed that the available content of Cd accounts for the largest proportion in the total amount up to 40.94%, followed by 12.73% of Pb, while Cr, Pb, As, Hg were dominated by residual fraction; There was a significant correlation between the speciation and total amount of five kinds of heavy metals, especially Pb. There were significantly negative correlations among the carbonate-bound form, strongly bound-organic state and humic acid of soil pH and Cd, Cr, Pb elements, the order affected by pH is Cr > Pb > Cd. There was a significantly positive correlation between the residual fraction content of heavy metal elements and Fe₂O₃ content. Five kinds of heavy metal exchange species and TOC are of negative correlation. There was a positive correlation between CEC and the water soluble state and residual state of heavy metal elements. Clay content is negatively correlated to the exchange state of Cr, and positively correlated to the residual state of each element.