几种粘粒矿物和土壤表面吸附态磷的解吸(英文)

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 Phosphate from Some Clay Minerals and Typical Soil Groups of China. 2.Effect of pH on Phosphate Desorption

The desorption-pH curves of phosphate from some clay minerals and typical soil groups of China could be grouped into three classes. With the first class concerning hydrous Fe, Al oxides and montmorillonite, desorption increased with increasing pH within the pH range of 4.0 to 10.0, and for kaolinite and the tested acid soils which contained higher contents of Fe, Al hydroxides and kaplinite, the desorption-pH coures were characteristic of "U" type with minimum P desorption at pH6.5 for kaolinite and at 4.8 for the soils whereas phosphate desorption from the tested neutral soil and calcareous soil was similar to that from calcite at acid side of pH, i.e. desorption was reduced with rising pH value, and at higher pH range P desorption became steady or even increased. It was also observed that the effect of pH on both adsorption and desorption was essentially the same, though in reverse direction, and the pH range of minimum desorption lay just between the PZCf and PZCi . value for kaolinite and acid soils. This suggested that P desorption from the variable-charge surfaces was to a great extent charge-dependent and the effect of pH on phosphate desorption was mainly through the change of surface charge rather than through the protonation and deprotonation of phosphoric acid in solution as suggested by Kingston, with regard to the neutral and calcareous soils the dissolution of calcium phosphate prevailed at low pH range but desorption of P from clay minerals became dominant at high pH.