中国表层土壤汞和硒分布空间异质性的因素分析

Spatial distribution heterogeneity of Hg and Se in surface soil in China and its plausible reason

在大尺度(中国)范围内,季风和降水等因素可能对土壤中挥发性元素汞和硒的含量具有显著影响,但影响表层土壤中汞和硒差异的关键因子及其贡献率仍未知。分析了干、湿沉降,微生物挥发作用对土壤中汞和硒积累的贡献,结果显示表层土壤汞和硒的积累是一个动态的过程。在全国尺度上,湿沉降对表层土壤中硒的贡献率达到91.5%,对汞的贡献率为49.4%;植被覆盖指数对土壤中汞的贡献为23.4%。由于汞和硒在大气中存在方式不同,汞以不溶于水的元素汞为主,而硒以易溶于水的甲基硒为主,干、湿沉降对二者的贡献有明显差异。

At a large scale(China), climatic factors such as monsoon and precipitation probably provide significant contributions to spatial distribution of mercury(Hg) and selenium(Se) in soil considering their volatile properties. However, it is still unclear which factors influence Hg and Se accumulations in surface soil and what their contribution rates are. This study mainly analyzes the contributions of dry and wet depositions and volatilization to accumulations of Hg and Se in surface soil, and argues that the accumulation of Hg and Se in surface soil is a dynamic process. At a national scale, the contribution rates of wet deposition to surface soil Se and Hg are 91.5% and 49.4%, respectively. The contribution of normalized difference vegetation index(NDVI) to soil Hg is 23.4%. Since mercury and selenium exist in different ways in the atmosphere, Hg is dominated by insoluble Hg0, while Se is dominated by soluble methylated Se. The contributions of dry and wet depositions to Hg and Se are significantly different.This study systematically presents the climatic factors affecting the distributions of Hg and Se in surface soil, and has important guiding significance for comprehensive understanding of the biogeochemical cycles of Hg and Se.