以自然土壤灰钙土和风沙土作为试验供试土壤,研究了Zn在两种土壤样品中的吸附-解吸特性.结果表明:(1)当平衡液中Zn浓度较低时,土壤对Zn的吸附量随浓度的增加而增加,但增加速度较慢;平衡液中Zn浓度继续增加时,吸附量增加速率变大(曲线斜率逐渐增大),由于灰钙土有机质、碳酸钙、pH等高于风沙土,所以灰钙土对Zn的吸附量大于风沙土;(2)在实验设定的浓度范围内,Langmuir模型、Freundlich模型对实验数据的拟合线性相关均极显著,但总体来看Freundlich型吸附等温线方程适合描述土壤对Zn吸附过程;(3)两种土壤的高碳酸钙及有机质含量导致土壤吸附的Zn不容易被解吸,所以两种土壤的解吸量都很少,且灰钙土pH(8.65)大于风沙土(8.17),则风沙土解吸量大于灰钙土,土壤吸附Zn的解吸率与土壤Zn吸附能力呈反比,Zn在风沙土中的解吸率比灰钙土大,所以Zn在沙土的迁移和扩散的风险比灰钙土大,二次函数最为适合模拟土壤中Zn的吸附量与解吸量之间的关系,且随着Zn吸附量的增大,两种土壤对重金属Zn的解吸率均呈现出先增大后减小的趋势.
A batch experiment was conducted to study the characteristics of the sorption and desorption of Zn in sandy soil and sierozem in the arid regions. The results indicated that:(1) The adsorption amount increased slowly with the promotion of concentration of Znat low equilibrium concentrations. With the addiction of Zn in the solution, the growth rate of the adsorption amount increased. The higher organic matter, calcium, pH, etc. was the reason of higher adsorption amount of sierozem soil compared with sandy soil. (2)Within the presume scale,the adsorption isotherms of Zn in the two tested soils could be described by the Langmuir and Freundlich equations which shows extremely significant linear relationship with the test data, especially the Freundlich equation was fitted best. (3) The desorption rate is inversely proportional to the ability of adsorption of soil. Zn is difficult to be desorbed because of the high content of calcium carbonate and organic matter in two soils, which lead to the low desorption. The desorption amount of sandy soil is more than sierozem because of the lower pH in sandy soil. Therefore, there is higher risk of migration and proliferation of the Zn in the sandy soil compared with sierozem. The relationship between the amount of adsorption and desorption of Zn in soil could be simulated by the quadratic function. With the increase of adsorption amount, the rate of desorption in the two soil increased firstly and then decreased.