我国几种主要土壤胶体的NH4+吸附特征

本文讨论我国几种主要土壤胶体的NH₄⁺吸附特征。土壤胶体对NH₄⁺的吸附符合两种表面Langmuir方程。土壤胶体对NH₄⁺的结合能力强弱顺序是:黄棕壤>黑土、(土娄)土>红壤>砖红壤,而NH₄⁺的解吸率大小顺序与此相反。Langmuir吸附方程参数K₁与土壤胶体的粘粒矿物组成有关,并与土壤胶体对NH₄⁺的相对偏好性(A值)呈正相关。Langmuir参数(M₁+M₂)与土壤胶体的CEC呈正相关,去有机质(OM.)前后△K₁与△OM.呈反相关。去有机质可增加土壤胶体对NH₄⁺的偏好性。土壤胶体的NH₄⁺吸附和解吸特征决定于其组成和表面性质,并受有机无机复合作用的影响。永久电荷吸附位对NH₄⁺的偏好性较强,而可变电荷吸附位则较弱。

CHARACTERISTICS OF AMMONIUM ADSORPTION BY COLLOIDS OF SOME MAIN SOILS IN CHINA

Ammonium adsorption and desorption were investigated with colloid samples of black soil,manured loessial soil, yellow brown earth, red earth and latosol as well as clay minerals. Adsorption of ammonium by soil colloids and clay minerals fitted to the two surface Langmuir adsorption equation. Binding strength was in the order: yellow brown earth > black soil,manured loessial soil>red earth>latosol, but the ammonium desorption ratio showed the opposite sequence. Langmuir parameter (K₁) was directly proportional to the relative affinity of soil colloids for ammonium (A). Langmuir equation constant (M₁+M₂) was positively correlated with CEC of samples, while the difference between K₁ before and after removing organic matter (ΔK₁) was negatively correlated with ΔOM.Removing organic matter could increase the affinity of soil colloids for ammonium and tended to decrease the ammonium desorption ratio.Annnonium adsorption behavior was determinedby the composition and surface properties of soil colloids, it was also influenced by clay-humus intereaction. Adsorption sites with permanent negarive charge showed stronger selectivity for ammonium than those sites with variable charge.