Some aspects of the chemistry of aluminium in podzolic soils

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Abstract
Studies conducted on the major characteristics of podzolic soils from northeastern Ontario, Canada, have shown that these soils are highly acidic, show intense weathering of minerals and considerable redistribution of both Al and Fe. Approximately 60% and 80% respectively of the accumulated Al and Fe in Bf horizons is in inorganically‐bound forms and secondary minerals formed during podzolization include an expandable 2: 1 clay mineral in the albic horizons and Al‐rich allophanes and ferrihydrite in spodic horizons. Studies on displaced soil solutions indicate significant contents of organically‐bound Al, the amounts of which decrease with depth as the proportion of inorganically‐bound Al increases. The application of phase diagrams and model calculations indicates that amorphous and/or poorly crystalline minerals may control the activity of Al3+ in the soil solutions, and that the content of organically‐bound Al in solution could be described adequately by assuming complexation with relatively simple organic acids, such as salicylic acid.