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几种重要粘粒矿物和我国代表性土壤表面吸附态磷的解吸随pH的变化可以归纳为三种不同的曲线类型.铁铝氧化物和蒙脱石表面磷的解吸在pH4.0到10.0范围内随pH升高而增加,pH6.0到7.5以上增加更快.高岭石和以可变电荷为主的酸性红黄壤的磷解吸—pH曲线呈现“U”型特征,其解吸最低值的pH高岭石为6.5,红黄壤类样品都在4.8左右.中性和石灰性土壤磷解吸在pH酸侧类似碳酸钙的情况,即解吸随pH升高线性下降,但在pH高于6.0～7.5以上时,解吸又趋于稳定,甚至增加.pH对磷吸附和解吸的影响在本质上是一样的,但方向相反.高岭石和红黄壤等具可变电荷表面的样品的磷解吸最小值pH范围恰好都落在各样品吸附磷前后的两个PZC值之间.上述结果表明可变电荷矿物和土壤吸附态磷的解吸在很大程度上受表面电荷特性 制约.pH影响此类样品磷解吸的机理主要是改变了表面电位.至于中性和石灰性土壤,磷的释放在pH酸侧主要受磷酸钙溶解作用支配;而在较高pH条件下,粘粒矿物表面吸附磷的解吸仍然是重要的.
Desorption of some important clay minerals and adsorbed phosphorus on the surface of representative soils in China can be classified into three different curve types with the change of pH.The desorption of phosphorus on the surface of iron-aluminum oxide and montmorillonite is in the range of pH 4.0 to 10.0 Increased with the increase of pH, and increased more rapidly from pH6.0 to 7.5. The phosphorus-desorption-pH curve of kaolinite and acidic reddish brown soil with variable charge showed “U” shape with the lowest desorption pH Kaolinite 6.5, red-yellow soil samples are around 4.8 Neutral and calcareous soil phosphorus desorption in the pH acid side similar to the case of calcium carbonate, desorption decreased linearly with increasing pH, but at pH higher than 6.0 ~ 7.5 , The desorption tended to be stable or even increased.The effect of pH on the adsorption and desorption of phosphorus was essentially the same but in the opposite direction.The minimum value of phosphorus desorption for samples with variable charge surfaces such as kaolinite and reddish brown pH The range falls exactly between the two PZC values before and after the adsorption of phosphorus on each sample.The above results show that the desorption of adsorbed phosphorus by variable charge minerals and soil is strongly controlled by the surface charge characteristics.PH affects the desorption The mechanism is mainly to change the surface potential In the acidic and calcareous soils, the release of phosphorus is predominantly dominated by calcium phosphate solubilization at the pH acid side, whereas desorption of adsorbed phosphorus on the clay mineral surface remains important at higher pH.