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选取名山河流域4种土地利用方式(茶园、旱地、水田、林地)的紫色土为对象,采用平衡液吸附法及NH4OAc、EDTA解吸法研究有机质对Pb2+在全土及各粒径团聚体中吸附-解吸的影响,用Langmuir、Freundlich和Temkin方程对等温吸附过程进行拟合。结果表明:去除有机质前后,4种土地利用方式紫色土全土及各粒径团聚体对Pb2+的吸附量均随Pb2+初始浓度的增大而增加,各粒径团聚体对Pb2+的吸附量排序为(<0.002 mm)>2~0.25 mm>全土>0.053~0.002 mm>0.25~0.053 mm,Freundlich方程拟合效果最佳,分布系数Kd值与Pd2+初始浓度呈曲线负相关,林地对Pb2+的吸附容量最大,茶园最小;4种土地利用方式紫色土全土及各粒径团聚体以静电吸附方式为主,络合吸附方式为辅,非解吸率大小关系均为林地>旱地>水田>茶园,说明茶园紫色土对Pb2+的固持能力最弱,林地最强。去除有机质后,4种土地利用方式紫色土全土及各粒径团聚体对Pb2+的吸附量均有所降低,相较于茶园和水田,林地和旱地吸附减少量更为明显,Pd2+最大吸附减少量与有机质去除量呈极显著正相关,4种土地利用方式紫色土NH4OAc解吸率明显增加,EDTA解吸率相应减少,非解吸率均有不同程度的降低。
The purple soil of four land use types (tea plantation, dry land, paddy field and woodland) in the Mingshan River Basin was selected as the object. The adsorption of Pb2 + in the whole soil and the aggregates of various particle sizes by organic matter was studied by equilibrium liquid adsorption method and NH4OAc, EDTA desorption method. Desorption, the isothermal adsorption process was fitted using the Langmuir, Freundlich, and Temkin equations. The results showed that before and after removal of organic matter, the adsorption capacity of Pb2 + by soil aggregates and purple soil aggregates increased with the increase of initial concentration of Pb2 +, and the order of Pb2 + adsorption by various aggregates was ( <0.002 mm)> 2 ~ 0.25 mm> total soil> 0.053 ~ 0.002 mm> 0.25 ~ 0.053 mm, the fitting effect of Freundlich equation is the best, the distribution coefficient Kd is negatively correlated with the initial concentration of Pd2 +, and the adsorption capacity of Pb2 + , And the tea plantations were the smallest. The four kinds of land use methods were purple soil and aggregates of various particle sizes. Electrostatic adsorption was the main method. The complexation mode of adsorption was secondary and non-desorption rate was woodland> dry land> paddy field> Soil Pb2 + holding capacity of the weakest, the strongest forest. Compared with tea plantation and paddy field, the adsorption amount of Pb2 + in all four kinds of land-use purple soil and aggregates of various particle size decreased after the removal of organic matter, and the decrease of adsorption of Pb2 + There was a significant positive correlation between the removal rate of organic matter and the removal rate of organic matter. The desorption rate of NH4OAc in purple soil increased obviously with the decrease of desorption rate and desorption rate of EDTA.