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| Franken, G; Pijpers, M; Matzner, E: Al chemistry of the soil solution in an acid forest soil as influenced by percolation rate and soil structure, European Journal of Soil Science, 46, 613-619 (1995) | |
Abstract:
The predicted activity of A1 in the soil solutions of acid forest soils often differs from that observed
in the field. We have investigated the influence of soil structure and flow rate of the soil solution on
the aluminum release to explain this divergence. Disturbed and undisturbed samples of soil were
collected from the A and B horizons of a dystric cambisol at Waldstein (Fichtelgebirge, Germany).
The samples were irrigated with solutions mixed according to field data on throughfall or soil
solution composition with pH 3.5 with flow rates of 4 mm d-I, 12 mm d-l and 36 mm d-I. The
percolates were analysed for major ions. Resulting relations between pH and pAl were compared
with batch experiments. In neither the A horizon nor in the B horizon did soil structure influence
the relation between pH and pAl. The apparent equilibrium between pH and pAl was described as
the pK,,, value with pK,,, = pAl- a pH (where a is an empirical constant). It was found that the
pK,,, values for the column percolates were in the range of variation of those found in batch
experiments.
Flow rate had no influence on pK,,, at 4 and 12 mm d-'. At 36 mm d-' a significant increase of
pK,, was observed. This relative undersaturation of Al was more pronounced in the A horizon
than in the B horizon. When flow is fast Al release into the percolating soil solution might be
limited by diffusion. |
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