毛细水带对Cr(Ⅵ)的阻污性能试验研究

Experimental study of the retardation rule of capillary transition zone to Cr(Ⅵ)

以土柱实验为研究手段,选择典型重金属污染物Cr(Ⅵ)作为研究对象,以惰性组分Br^-作为对比,分别探讨了Cr(Ⅵ)在存在支持毛细水、悬挂毛细水、无毛细水条件下,以及不同NaCl浓度条件下的迁移规律,进而从污染物穿透时间及残留量两个方面定量刻画毛细水带对Cr(Ⅵ)的阻滞作用。研究结果表明:不同形式毛细水条件下Br^-及Cr(Ⅵ)的穿透时间均为干土柱<有悬挂毛细水土柱<有支持毛细水土柱;与Br^-相比,Cr(Ⅵ)穿透终点均呈现明显滞后的现象,表明不同形式毛细水对Cr(Ⅵ)均具有不同程度的阻滞作用;受盐分析出及重力势的共同影响,不同NaCl浓度条件下Br^-及Cr(Ⅵ)的穿透时间均体现为10 g/L>60 g/L>0 g/L。Cr(Ⅵ)残留量整体呈现随土柱高度增加递减的趋势。存在支持毛细水及NaCl浓度为10 g/L的条件下土柱中Cr(Ⅵ)残留量最高,表明该情况下毛细水带的阻污作用最为显著。

The capillary transition zone that forms the vadose zone with the soil water zone and the intermediate zone,is a zone occurring when water rises to a certain height from the water table along the small pores in the unconsolidated sediments. The capillary transition zone is the inevitable passage that containments enter groundwater from the land surface. Studies of the capillary transition zone are of important practical significance. This paper chose Cr（ Ⅵ） as the research subject and used Br-as a comparison to examine the principles of transfer of Cr（ Ⅵ） under different concentrations of sodium chloride（ 0 g / L,10 g / L and 60 g /L） and different forms of the capillary water. The breakthrough time and residue were used to quantitatively express the inhibition of the capillary transition zone on Cr（ Ⅵ）. The research results show that the breakthrough time of Cr（ Ⅵ） and Br-under different types of capillary water was shown as follow： no capillary water the suspended capillary the support capillary water. Compared with Br-,the breakthrough curve of Cr（ Ⅵ） showed the clear hysteresis phenomenon,indicating the inhibition of the capillary transition zone on Cr（ Ⅵ）. Because of evaporation and gravitational potential,the breakthrough time under differentconcentrations of sodium chloride was shown as follow： 10 g / L 60 g / L 0 g / L. The residue of Cr（ Ⅵ）decreased with the height of column. The residue of Cr（ Ⅵ） under 10 g / L and the suspended capillary water is the highest level,indicating that the inhibition of the capillary transition zone has the greatest significant inhibition on Cr（ Ⅵ） under that condition.