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ABSTRACT
Field and laboratory data on one acid sulfate soil are used to compute the concentration of dissolved Fe2+ with depth and time by means of a mathematical model that considers simultaneous production and diffusion of aqueous Fe2+ during submergence.
Calculated ferrous iron concentrations compare well with concentrations measured in the course of 175 days at six depths down to 150 cm below the soil surface. Discrepancies between the model and field data for one depth may be attributed to mass flow induced by sampling of the soil solution.
The results are useful in interpreting the processes involved in the typical ferric oxide and jarosite accumulations observed in the B horizon of most acid sulfate soils in Thailand. During flooding small but significant amounts of iron diffuse towards the B horizon. The calculated fluxes of iron are too small to explain the observed ferric iron accumulation by diffusion of Fe2+ during the flooding period only. Diffusion and evaporative mass flow of Fe2+ liberated by pyrite oxidation in the C horizon during the dry season appear to be more important.
1 Contribution from the Department of Soils and Fertilizers, and the Department of Soil Science and Geology, Agricultural University, Wageningen, The Netherlands. The work was supported in part by the Netherlands Foundation for the Advancement of Tropical Research (WOTRO, grant 89-2).
2 Soil Scientists, Dept. of Soils & Fertilizers, and Soil Science & Geology, Agricultural Univ., P. O. Box 37, Wageningen, The Netherlands.
Received for publication March 3, 1975. Accepted for publication August 4, 1975.
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