蒙山茶园土壤组分对铝吸附解吸热力学特征的影响

Effect of Thermodynamics Characteristics of Sluminum Sdsorptiondesorption by Components of Tea Garden Soil in Mengshan

采用间歇法和振荡平衡法,通过实验室模拟,研究了蒙山茶园土壤(紫色土和黄壤)原土及各粒级组分对铝吸附解吸的热力学特征,并分析土壤有机质、游离氧化铁和CEC对其吸附解吸的影响。结果表明:(1)不同土壤原土及各粒级组分对铝的吸附量都随铝离子浓度的增大而增加,且各粒级土壤对铝的吸附量不同,表现为土壤颗粒比表面越大,有机质、游离氧化铁和CEC越高,其吸附量越大。紫色土原土及各粒级组分对铝的等温吸附过程用Freundlich方程描述最佳,说明紫色土对铝的吸附是多层吸附;而黄壤原土及各粒级组分对铝的等温吸附过程则用Langmuir方程描述最佳,说明黄壤对铝的吸附以单层吸附为主。(2)紫色土原土及各粒级组分对铝的解吸率表现出以下关系:粗砂粒>原土>细砂粒>粉粒>粘粒,黄壤原土及各粒级组分对铝的解吸率则表现出以下关系:细砂粒>粗砂粒>原土>粉粒>粘粒,两者解吸率的大小关系均与其有机质及游离氧化铁相反,表明两种土壤的原土及各粒级组分中有机质和游离氧化铁越高,其专性吸附率就越高,从而解吸率越小,说明土壤有机质和游离氧化铁影响土壤对铝的固持能力。(3)土壤最大吸附量与有机质、游离氧化铁含量和CEC都表现出显著或极显著的正相关关系,而其最大解吸率也均与有机质、游离氧化铁含量和CEC表现出显著或极显著的负相关关系。

Thermodynamics characteristics of aluminum adsorption and desorption and the influencing factors （soil organic matter, free ferric oxide, CEC） of tea garden soil and particle-sized fractions in Mengshan were studied with batch and oscillation balance methods. Results showed that： the aluminum adsorption increasing with the increase of equilibrium concentrations for different kinds of bulk soil and particle-sized fractions. The amount of aluminum adsorption in particle-sized fractions was different that the larger the surface area of soil particles was and the higher levels of soil organic matter, free ferric oxide and CEC, and the more adsorption amount would be more. Freundlich equation was the best equation to fit aluminum adsorption of purple soil and particle-sized fractions, thus the aluminum adsorption was a multilayer adsorption. Meanwhile, Langmuir equation was the best equation to fit aluminum adsorption of yellow soil and particle-sized fractions, thus the aluminum adsorption was a monolayer adsorption. The aluminum desorption rates of purple soil and particle-sized fractions followed the order of coarse sand 〉 bulk soil 〉 fine sand 〉 silt 〉 clay. The desorption rates of yellow soil and particle-sized fractions were in the order of fine sand 〉 coarse sand 〉 bulk soil 〉 silt 〉 clay. The negative correlation between the desorption rates of the two soils and the amounts of soil organic matter and free ferric oxide showed that, the higher levels of soil organic matter and free ferric oxide were, the higher the rate of specific adsorption （the lower desorption rate ） would be. Soil organic matter and free iron oxide affected the aluminum retention capacity of the soil. The results showed the significant or even highly significant positive correlation between the maximum amount of adsorption and soil organic matter, free ferric oxide, CEC, while the significant or even highly significant negative correlation between the maximum amount of desorption and soil organic matter, free ferric oxide, CEC.