Aluminium solubility characteristics of spodic B horizons containing imogolite-type materials
Aluminium solubility characteristics of spodic B horizons containing imogolite-type materials (in Clay minerals in the modern society, D. C. Bain (editor))
Clay Minerals (March 1998) 33 (1): 77-86
Fifteen Swedish and Finnish soil samples from spodic B horizons containing imogolite-type materials were equilibrated with dilute NaCl and HCl at 8 degrees C. For the NaCl extracts, apparent equilibrium with respect to an Al(OH) (sub 3) phase was reached in one to two weeks. Equilibrium with respect to an imogolite-type phase was slower, especially at large soil:solution ratios. The results show that log *K (sub s) (gibbsite), i.e. the logarithm of the solubility constant for reactive Al(OH) (sub 3) at 8 degrees C, was approximately 9.40 (8.29 at 25 degrees C) while log *K (sub s) (imogolite) was variable; for the soil studied in most detail it was 7.66 (6.64 at 25 degrees C). As well-ordered gibbsite rarely forms in spodic B horizons, it is suggested that Al(OH) (sub 3) and poorly-ordered allophanic materials may be slowly converted to less soluble and less reactive imogolite-type materials.