溶液pH对红壤吸持磷机理的影响

本文研究了湘南红壤对磷酸盐的吸附机理。结果表明，在通常ｐＨ范围内，第四纪红粘土母质对Ｈ２Ｐ０４＾－的吸附等温式以Ｌａｎｇｍｕｉｒ方程式最好；而且吸附量远远大于旱地红壤。当介质ｐＨ很低时，红壤磷酸盐吸附量随ｐＨ的升高而增加，至ｐＨ２．９附近时出现最大吸附值，然后随介质ｐＨ的升高，吸附量逐渐减少。说明磷酸盐最大吸附ｐＨ的产生是由土壤交换性铝的含量及水解、土壤电荷零点及磷酸盐水解常数等因素决定。

EFFECT OF PH OF EQUILIBRATING SOLUTION ON MECHANISMS OF H_2PO4- ADSORPTION ON RED SOILS

Effect of pH of equilibrating solution on the mechanisms of H2PO4 adsorption on red soils in southern Hunan Province was investigated using adsorption isotherm method. Result showed that in normal pH range of soils. Langmuir equation was the most suitable model for describing the adsorption of H2PO4- on Quaternary Red Clay, adsorption capacity of which was far greater than that of caltivated upland. When the pH was very low ,H2PO4- adsorption was mcreased with on increase of the pH value until a largest adsorption was appeared around pH 2. 90, and then it was decreased with a further increase of the pH value . It was considered that the pH value at which the largest H2PO4- adsorption appeared was determined by several factors, such as the content and hydrolysis of soil exchangable aluminium, ZPC of the soils, and hydrolysis constant of phosphates etc.