湖南省3种主要类型水稻土对镉、铜的吸附-解吸特性研究

Adsorption-desorption of Cd and Cu in three types of paddy soils from Hunan Province

为比较不同水稻土中镉铜元素化学行为的差异,采用振荡平衡法,通过室内恒温吸附解吸试验,研究了湖南省3种水稻土(红黄泥、灰泥和河沙泥)对镉、铜单一元素以及两元素交互作用下的恒温吸附和解吸规律。结果表明,单一体系下,灰泥对镉、铜的吸附量均大于红黄泥和河沙泥;红黄泥和河沙泥对镉的解吸率大于灰泥;红黄泥对铜的解吸率大于河沙泥大于灰泥;红黄泥和河沙泥镉、铜的吸附值以Freundlich方程拟合性最好,灰泥镉、铜的吸附值Langmuir方程拟合度最高;同一种土壤铜的吸附量均大于镉的吸附量,而解吸率相反。在竞争体系下,3种土壤中铜的存在使镉的吸附量显著减小,且铜对镉的影响作用随土壤pH值的增加而增强,镉的存在对钢的吸附量影响不大。

In order to compare the chemical behavior of cadmium and copper in different soil environment, adsorption-desorption of cadmi- um and copper in three paddy soil types of Hunan Province were investigated in batch experiments. Results showed that the amount of adsorbed Cd and Cu in mortar soil for single metal system were higher than that of reddish clay and sandy mud. Soil pH, CEC and organic matter are the three main factors affecting the adsorption of Cd and Cu. The rate of Cd desorption for reddish clay and sandy mud was higher than that of Mortar soil. The sequence of Cu desorption rate was in the order of reddish clay 〉 sandy mud 〉 mortar soil. The adsorption characteristics of Cd and Cu for reddish clay and sandy mud were similar and the isothermal adsorption of Cd and Cu were confirmed as Freundlich model. Correlation coefficient for Cd adsorp- tion on both reddish clay and sandy muddy soil was recorded as 0.995 respectively. On the other hand, the correlation coefficient for Cu ad- sorption in reddish clay and sandy mud was 0.987 and 0.972 respec- tively. For mortar soil, the isothermal adsorption of Cd and Cu were determined to match with Langmuir equation in which the correlation coefficient for Cd and Cu adsorption was 0.991 and 0.990 repectively. The adsorption of Cu was higher than that of Cd, but the desorp- tion of Cd was higher than that of Cu on the other hand/in the multiheavy metal system, the adsorption of Cd was reduced significantly. The competition between metals for adsorption increased with the increase of soil acidity level.