摘要
在中性条件下,低浓度的柠檬酸、草酸、酒石酸和胡敏酸阴离子都能显著降低针铁矿、非晶氧化铝、高岭石和红壤对磷酸根的吸附,尤其在低磷吸附饱和度下效果更好。有机阴离子抑制磷酸根吸附的能力因有机酸的种类和性质、以及固相的表面特性而异。有机阴离子存在下吸附的磷酸根具有较高的同位素^(32)P交换活性和解吸率。测定了吸附平衡溶液中铁和铝的浓度。结果表明,在实验条件下(pH 7.0),即使较高浓度的有机酸根(10^(-2)mol)也只能溶解极少量的铁和铝。有机阴离子络溶作用不足以说明固相吸附磷能力的显著下降。可见,有机阴离子降低磷酸根吸附的机制主要是竞争专性吸附。有机阴离子占据了一部分高亲和力的吸附位,从而降低了土壤固相吸附磷的量,增加了吸附态磷的活性。
The effect of some common organic ligands on phosphate adsorption by hydrous Fe and Al oxides, Kaolinite and acid earth (red earth or ultiosl) was studied. In neutral solution with low concentrations of citrate, tratrate, oxalate and humate, the organic ligands appeared to be very effective in reducing phosphate adsorption on goethite, amorphous Al-oxide, kaolinite and acid soil, especially at low saturation of phosphate adsorption, Evaluation by K value from the lang muir adsorption equation demonstrated that phosphate sorbed at the presence of organic ligands was much loosely bonded, and therefore was more available to plants as shown by the higher values of isotopic exchangeability and desorbability of the sorbed phosphate. Increasing concentrations of citrate from 10^(-5)mol to 10^(-1) mol decreased phosphate adsorption on goethite, amorphous Al-oxide, kaolinite and acid soil by 37.9, 43.4, 47.7 and 80.4%, and increasing that of cartrate from 10^(-5) mol to 10^(-1) mol decreased the their phosphate adsorption 27.6, 42.4, 42.7 and 50.6%, respectively. No significant amounts of Fe or/and Al were dissolved in the equilibrium solution in the experiments. The maximum dissolution of amorphous Aloxide in 10^(-1) mol citrate solution was less than 0.2%. Since the newly exposed surface are very low in their affinity for phosphate and the dissolution amount of the soilds dissolved is so small that can not indicate the reduce of the total surface areas of the sorbents, the contribution of complex reaction of the organic ligands with Fe and Al ions is very limited in the reduction of phosphate adsorption. It seems reasonable to conclude that the competition of organic ligands with phosphate for those sorption sites with high binding-energy is. responsible for the reducing adsorption and increasing lability of the sorbed phosphate.
出处
《土壤学报》
CAS
CSCD
北大核心
1990年第4期377-384,共8页
Acta Pedologica Sinica
