名山河流域水稻土微团聚体对砷(As^(5+))的吸附-解吸特性

Adsorption and desorption characteristics of As^(5+) on the Paddy Soil Micro-aggregates in Minshan watershed

以名山河流域典型水稻土为研究对象,通过模拟试验,采用平衡液吸附法及NaCl解吸剂解吸法研究全土及不同粒径微团聚体(2~0.25mm,0.25~0.053mm,0.053~0.002mm,<0.002mm)对砷(As5+)的吸附解吸特征,同时研究了土壤微团聚体对砷(As5+)热力学与动力学吸附解吸过程的特征。结果表明:水稻土及不同粒径微团聚体对砷(As5+)的吸附量随时间、浓度的增加而逐渐趋于平衡,动力学吸附以Elovich方程拟合最佳,热力学吸附以Freundlich方程拟合最佳;动力学吸附量随时间逐渐降低,在600min达到吸附动态平衡;热力学吸附量随时间逐渐增加,初始砷(As5+)浓度达到160mg/L后几乎处于吸附动态平衡,吸附过程分为快速和慢速2个阶段;砷的动力学、热力学吸附均以专性吸附为主,非专性吸附为辅;根据解吸难易程度分为易解吸与难解吸,各粒径微团聚体易解吸率大小依次为:(0.25~0.053mm)>(2~0.25mm)>原土>(0.053~0.002mm)>(<0.002mm),与有机质、游离氧化铁、CEC含量的大小呈正相关,难解吸率大小与之呈负相关。

Arsenic（As^5＋）of adsorption and desorption characteristics was studied on whole soil and microaggregates（2～0.25 mm,0.25～0.053 mm,0.053～0.002 mm,0.002mm）of the Mingshan River watershed typical paddy soil by laboratory simulation,equilibrium liquid adsorption and the NaCl as desorbent,s desorption method,and the soil micro-aggregates＇ adsorption and desorption of characteristics based on studied on arsenic by thermodynamics and kinetics.The results showed that：The whole soil and different size＇s micro-aggregates of the paddy soil adsorption capacity increased as the time,and gradually tended to balance,and the best fit was Elovich equation on kinetic adsorption,while thermodynamic was Freundlich equation.The adsorption amount of kinetic decreased with the time increasing,and it was equilibrium at 600 minutes.While it was increasing with the time increasing of thermodynamic adsorption,and it was dynamic equilibrium when the concentration of arsenic（As^5＋）reached 160 mg/L.The adsorption process was divided into two stages of fast and slow.The kinetics and thermodynamics adsorption of arsenic（As^5＋）was adsorbed by specific adsorption-based,supplemented by non-specific adsorption.According to the degree of difficulty and easily,the adsorption divided into easy desorption and obscure suck.The order of easy desorption rate on microaggregates was（0.25～0.053mm）〉（2～0.25mm）〉whole soil〉（0.053～0.002mm）〉（〈0.002mm）,and it was positively correlated with the content of organic matter,free iron oxides,CEC,but the obscure absorption rate was negatively correlated with it.