磷酸盐吸附对可变电荷土壤正负电荷的影响

本文研究了华南地区不同类型的可变电荷土壤，并对磷酸盐的吸附量和吸附磷后土壤的正、负电荷的变化，以及ｐＨ和游离氧化铁对这种变化的影响进行了研究。结果表明，土壤吸磷量与土壤游离氧化铁含量成良好的正相关。土壤吸磷后正电荷减少，负电荷增加，土壤电荷量与吸磷量之间呈抛物线状相关。吸附１摩尔磷酸盐对土壤净负电荷的贡献在０．３－１．０摩尔之间。土壤中的游离氧化铁使吸附的磷对土壤负电荷的贡献减少。

EEEECT OF PHOSPHATE ADSORPTION ON POSITIVE AND NEGATIVE CHARGES OF VARIABLE CHARGE SOILS

Adsorption of phosphate by different types of soils with variable charge and the changes of negative and positive charges of soil after phosphate adsorption as well as the effect of pH and free iron oxides on the changes of soils were studied. The resalts showed that phosphate was all adsorbed by soils when a smaller amount phosphate was added, and the amount of phosphate adsorbed accounted for 40-85% of phophate added. Phosphate adsorption by soils was closely related with free iron oxides in soils.The positive charge decreased but negative charge increased after phosphate adsorption by soils. The increment and decrement of charges were larger at lower phosphate adsorption. The charges of soils have a parabola relation with phosphate adsorbed. The contribution of phosphate adsorbed to net negative charge of soils ranged between 0.3-1.0 mole per mole phosphate, being the smallest in latosol and the largest in yellow soil.The increment of negative charge of latosol after phosphate adsorption was lower at low pH, but increased with pH increase. For red soil and yellow soil, increment of negative charge after phosphate adsorption was not affected obviously by pH value, The free iron oxides in soils caused a decreased contribution of phosphate adsorbed to negative charge of soils.