氟与红壤相互作用过程及环境意义

Interaction of Fluoride with Red Soil and Its Environmental Implications

氟与铝具有高的亲合性,在酸性氟污染的土壤中氟与土壤的相互作用会引起土壤物理化学条件和土壤胶体表面特征的变化,因此会导致其他营养组分和污染元素吸附和迁移行为的变化。用批次平衡法研究了不同pH和不同初始氟浓度的含氟溶液与红壤相互作用过程中溶液pH值、溶解态总氟、自由氟、络合态氟和土壤吸附态氟的变化。结果表明,F-与红壤颗粒表面的-OH基团发生络合交换,使土壤溶液pH增大。由于Al-F络合、土壤对氟的吸附以及氟诱导的Al溶解,溶解态总氟和自由氟浓度均有不同程度的降低,且初始pH越低,降低的程度越大。由于红壤表面Al-F络合体的解吸及活性铝组分的快速溶解,溶液中的Al-F络合物在短时间内迅速增加。土壤中氟的吸附量随pH下降以及F-的浓度增加而增加。土壤酸度增加,既可增加Al-F的络合程度,也可提高氟的吸附量,因此可一定程度上减少氟在土壤中的活性和生物有效性。

Interaction of Al-F in acidic soils may cause significant changes of soil solution characteristics and surface properties of soil colloids due to high affinity of fluoride for Al. The alterations of solution pH, total soluble F, free F, bound F and adsorbed F in process of interaction between fluoride and red soil were investigated at different F initial concentrations （1, 5 and 10 mmol·L^-1）, different initial solution pH （3.5, 4.2 and 6.3） using a batch technique. The results showed that ligand exchange of F- ions with -OH groups on the surfaces of soil particles caused a significant increase of solution pH. Due to a combined result of Al-F complexation, F adsorption on soils and F induced Al dissolution, the concentrations of total soluble F and free F decreased with decreasing solution pH. Concentration of bound F in solution increased rapidly within short time because of desorption of adsorbed Al-F complexes as well as rapid dissolution of active solid Al components. F adsorption on soils increased with decreasing solution pH and increasing initial F concentration. An increase in soil acidity may increase F adsorption on soil particles and the extent of Al-F complexation, consequently decreasing the activity and bioavailability of F in F- contaminated red soils.