土壤对铜的吸附-解吸特征及对土地利用的响应

用吸附平衡法研究黄河三角洲地区土壤对Cu2+的吸附和解吸特征,对比了农田和未利用地土壤吸附与解吸能力的差异,并分析了差异形成的原因。结果表明,土壤对Cu2+的吸附量随着平衡液Cu2+质量浓度的增加而增加,其吸附作用可用Langmuir,Temkin和Freundlich方程来拟合,以Langmuir方程拟合结果最佳。根据Langmuir方程计算出的两种土壤最大吸附量分别为3 961mg/kg和3 521mg/kg,农田土壤对Cu2+的吸附能力强于未利用地土壤;土壤Cu2+的解吸量远远小于土壤对Cu2+的吸附量,与农田土壤相比,未利用地土壤Cu2+的解吸有滞后现象;农田土壤和未利用地土壤Cu2+的解吸率变化范围分别为0.1%～0.35%和0.15%～1.8%,农田土壤的解吸率明显低于未利用地土壤。综合分析认为,两种土壤吸附—解吸特征的差异与农田土壤具有较高的有机质含量,从而在土壤胶体表面形成较多的吸附位点有关。

Characteristics of Copper Adsorption-Desorption by Soils and Its Responses to Land Use

The characteristics of Cu²⁺ adsorption-desorption by soils in the Yellow River Delta were studied using isothermal equilibrium adsorption method.Differences in the adsorption-desorption capacity of soils in farmland and unused land were compared and the reasons for the differences were analyzed. Results showed that the adsorption capacity for the two types of soils increased with Cu²⁺ equilibrium concentration. he adsorption characteristics could be simulated by Langmiur, Freundlich and Temkin models.Langmuir model was found to be the best one. The maximum adsorption capacity of soil was 3961mg/kg for farmlandand 3 521mg/kg for unused land, respectively. The Cu²⁺ adsorption capacity of soil in farmland was much higher than that in unused land. The Cu²⁺ desorption capacity was far lower than the Cu²⁺adsorption capaci-ty. There was an obvious lag period of the Cu²⁺ desorption by soil in unused land, as compared with that in farmland. The Cu²⁺ desorption ratio for soil in unused land was greater than that in farmland, and the de-sorption ratio was between 0.1% and 0.35%in farmland and between 0.15% and 1.8%in unused land, respectively. The results from the comprehensive analysis suggest that the differences in the adsorption-desorption for the two types of soils are related with soil organic matter content which leads to more adsorp-tion points on the soil colloid surface in farmland.