紫色水稻土对镉吸附解吸特性的研究

目的]了解紫色水稻土对镉吸附解吸特性,为紫色水稻土中镉的归趋阐明提供科学依据。方法]采用一次平衡法进行酸性、中性和石灰性紫色水稻土对镉的吸附解吸试验,用吸附等温方程对试验数据进行拟合,并考察吸附能力和土壤性质的关系。结果]3种土壤对镉吸附量均随平衡浓度的增加而增加,吸附能力以石灰性土最高,酸性与中性土相近,且吸附等温线均可用Langmuir和Freundli-ch方程很好地拟合。3种土壤镉解吸量和解吸率均随吸附量的增加而增加,其中石灰性土的解吸率最低,而酸性和中性土的解吸率均高于50%。吸附能力与土壤性质有明显关系,其中pH为重要因素,非晶质铁锰氧化物和黏粒等对土壤镉吸附解吸的影响并不明显。结论]3种土壤中,石灰性土壤对镉的固持和缓冲能力最强,而外源镉进入酸性和中性土壤后的环境风险较高。土壤性质对镉的吸附和固定有重要影响,其中pH为关键因素。

Adsorption and Desorption Characteristics of Cadmium in Three Purplish Paddy Soils

Objective] The research aimed to study the characteristics of cadmium adsorption and desorption in purplish paddy soil,providing scientific evidence for clarifying environmental fate of cadimium in purplish paddy soil.Method]The batch method was used to study the characteristics of cadmium adsorption and desorption in three purplish paddy soils including an acidic purplish paddy soil(APPS),a neutral purplish paddy soil(NPPS) and a calcareous purplish paddy soil(CPPS).Langmuir equation and Freundlich equation were used to describe the adsorption data and the relationship between adsorption ability and basic properties of the tested soils were examined.Result]The adsorption of cadmium in three paddy soils increasd with the increase of initial concentrations of cadmium in solution,with the highest adsorption ability being observed in CPPS.The amount of cadmium adsorbed by NPPS was slightly higher than that of APPS.The adsorption data of the soils could be well described with Langmuir equation and Freundlich equation.The desorption of cadmium from those soils increaseed with the increase of cadmium adsorbed by soils.Among them,the desorption rate of cadmium by CPPS was the lowest and the percentages of cadmium desorbed from APPS and NPPS were higher than 50%.There was close relationship between adsorption ability and basic properties of the tested soils and soil pH played an important role.No obvious relationship was found between the ability of cadmium adsorption and the content of amorphous iron and manganese oxide or clay.Conclusion]CPPS had the strongest ability to fix cadmium,thus had greater buffer capacity to the exogenous input cadmium.And there was high environmental risk as exogenous cadmium was input into APPS and NPPS.Soil pH played an important role in controlling the behavior of cadmium adsorption and desorption in soils.