亚硒酸盐在不同理化性质土壤中运移规律研究

Selenite transport in soils with various physico-chemical properties

通过亚硒酸盐在江西丰城稻田表层0-10 cm土壤（FC1）、次表层10-20 cm土壤（FC2）、江西德兴菜地表层土壤（DC）、河北保定旱地表层土壤（BD）等几种土壤中的吸附解吸及土柱运移实验,研究了亚硒酸盐在土壤中的运移行为,探讨了亚硒酸盐在不同理化性质土壤中的运移规律。结果表明：具有较高含量活性Fe及有机质（OM）和较低pH值的FC1和FC2土壤对亚硒酸盐的吸附能力较强,其次为DC土壤和BD土壤,其最大吸附量分别为621.50、592.20、219.29、163.51 mg·kg^-1,且吸附能力最弱的BD土壤具有较高的亚硒酸盐解吸率和解吸量;亚硒酸盐在BD土壤填装土柱中运移速度最快,且在其他研究土壤中运移速度较慢,表明土壤对亚硒酸盐的吸附解吸能力控制着其在填装土柱中的运移速率。此外,江西丰城原状土柱中亚硒酸盐运移实验表明,原状土柱中亚硒酸盐的运移速度明显较填装土柱快,且其穿透曲线用HYDRUS-1D软件中双孔-两点吸附模型拟合结果较好,表明真实土壤环境中由于大孔径和优势流的存在,硒（Se）可能运移更快,进而污染地下水。

The transport of heavy metals in soil determines their risks to underground water and human health. However, such transport is controlled by soil properties. Here we studied the adsorption, desorption and transport of selenite in different soils ：FC1（0-10 cm surface soil from Fengcheng, Jiangxi）, FC2（10-20 cm subsurface soil from Fengcheng, Jiangxi）, DC（surface soil in Dexing, Jiangxi）and BD（surface soil in Baoding, Hebei）, to uncover the effects of soil physico-chemical properties on selenite transport in soils. Results showed that FC1 and FC2 soils, having higher amorphous iron oxide and organic matter（OM）and lower soil p H than others, had greater selenite adsorption, with the maximum adsorption capacities of 621.50 mg·kg^-1and 592.20 mg·kg^-1, respectively. The maximum selenite adsorption was219.29 mg·kg^-1for DC and 163.51 mg·kg^-1for BD. However, BD soil had the highest selenite desorption rate and amount. In packed soil column experiment, selenite transported faster in BD soil than in other soils, suggesting that the transport of selenite in soil column was influenced by the adsorption and desorption abilities of selenite in soils. In intact soil column, selenite transported quicker than in the packed soil columns. The breakthrough curve of selenite in intact soil column fitted DTSMZ（Dual-porosity with Two-Site Sorption in the Mobile Zone）model well by HYDRUS-1D software. Our results indicate the possibility of selenium pollution in groundwater due to the presence of macropore and preferential flow in the field conditions.