Effect of Electrolyte on the Dissolution of Aluminum from Acid Soils and the Distribution of Aluminum Forms in Soil Solution

摘要

KCl, CaCl_2, NH_4Cl, NaCl, K_2SO_4 and KF solutions were used for studying the effects of cations and anions on the dissolution of aluminum and the distribution of aluminum forms respectively. Power of exchanging and releasing aluminum of four kinds of cations was in the decreasing order Ca~(2+) >K~+ > NH_4~+ >Na~+. The dissolution of aluminum increased with the cation concentration. The adsorption affinity of various soils for aluminum was different. The aluminum in the soil with a stronger adsorption affinity was difficult to be exchanged and released by cations. The Al-F complexes were main species of inorganic aluminum at a low concentration of cations, while Al~(3+) became major species of inorganic aluminum at a high concentration of cations. The results on the effect of anions indicated that the concentrations of total aluminum, three kinds of inorganic aluminum (Al~(3+), Al-F and Al-OH complexes) and organic aluminum complexes (Al-OM) when SO_4~(2-) was added into soil suspension were lower than those when Cl~- was added. The dissolution of aluminum from soils and the distribution of aluminum forms in solution were affected by the adsorption of F~-on the soil. For soils with strong affinity for F~-, the concentrations of the three inorganic aluminum species in soil solution after addition of F~- were lower than those after addition of Cl~-; but for soils with weak affinity for F~-, the concentrations of Al~(3+) and Al-OM were lower and the concentrations of Al-F complexes and total inorganic aluminum after addition of F~- were higher than those after addition of Cl~-. The increase of F~- concentration in soil solution accelerated the dissolution of aluminum from soils.