三峡库区消落带土壤重金属Zn的形态分布特征及其影响因素

The Chemical Form Distribution Characteristics of Heavy Metal Zn in Soil and the Influence factors in the Water-level-fluctuating Zone of the Three-Gorges Reservoir Area

以位于三峡库区腹心地带的一级支流—小江消落带为研究区,通过野外采样和室内分析,对消落带上土壤重金属Zn及其化学形态的含量特征进行了分析,并采用相关分析和逐步回归法探讨了影响重金属化学形态的影响因素。结果表明,消落带土壤重金属Zn全量、酸溶态、可还原态、可氧化态、残渣态平均含量分别为126.03mg.kg-1,3.60mg.kg-1、5.44mg.kg-1、10.59mg.kg-1和106.40mg.kg-1。Zn全量及其化学形态含量在小江各区段的分布呈中游段最高,上游、中下游段较低的特征,这主要与小江流域消落带各区段的地质背景有关。Zn不同形态含量受Zn全量及土壤理化性质影响的显著性程度不同。可还原态主要受Zn全量的影响;可氧化态主要受泥粒含量的影响;残渣态受Zn全量和有机质含量的共同影响;酸溶态含量受Zn全量和土壤理化性质的影响均不显著。

This study is devoted to a tributary of the Xiaojiang Water-level-fluctuating Zone, which is located in the center of the Three-Gorges Reservoir area. By field sampling and laboratory analysis, this paper studied the heavy metal Zn in soil of this area and the speciation characteristics of its chemical form, and by using the correlational analysis method and stepwise method, this paper also discussed the factors affecting the chemical forms of the heavy metal. It is shown that the total contents, the acid soluble fraction, the reducible fraction, the oxidizable fraction and the residual fraction of Zn in this area are respectively 126.03 mg· kg^-1, 3.60 mg· kg^-1, 5.44 mg·kg^-1,10.59 mg·kg^-1 and 106.40 mg· kg^-1 on average, respectively. It is suggested that the total contents of Zn and its speeiation contents are mostly distributed in the middle reaches while less in the upper, middle and lower reaches of the river. This is related to the geological background of each section of the water-level- fluctuating zone. The different chemical species of Zn were affected at different levels of significance by the total contents of Zn and soil properties. The reducible fraction of Zn was mainly affected by its total contents, the oxidizable fraction by sediment contents, and the residual fraction by its total contents together with organic content. The acid soluble fraction was markedly affected by neither its total quantity nor its physical and chemical properties.