Fifteen Swedish and Finnish soil samples from spodic B horizons containing imogolite-type materials were equilibrated with dilute NaCl and HCl at 8°C. For the NaCl extracts, apparent equilibrium with respect to an Al(OH)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 *Ks (gibbsite), i.e. the logarithm of the solubility constant for reactive Al(OH)3 at 8°C, was ~9.40 (8.29 at 25°C) while log *Ks (imogolite) was variable; for the soil studied in most detail it was 7.66 (6.64 at 25°C). As well-ordered gibbsite rarely forms in spodic B horizons, it is suggested that Al(OH)3 and poorly-ordered allophanic materials may be slowly converted to less soluble and less reactive imogolite-type materials.
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Document Type: Research Article
Division of Land and Water Resources, Royal Institute of Technology, S-100 44 Stockholm, Sweden
Soil Science Group, Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
Department of Soil Sciences, Swedish University of Agricultural Sciences, Box 7014, S-750 07 Uppsala, Sweden
Publication date: 1998-03-01
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