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Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model

Kinetic equations are developed for a system in which a column of reduced soil is exposed to oxygen at one end. The equations are combined in a simulation model in which they are solved by finite‐difference methods. The model predicts the consequent diffusion of oxygen into the column; the diffusion...

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Main Authors: Kirk, G.J.D., AHMAD, A.R., NYE, P.H.
Format: Journal Article
Language:Inglés
Published: Wiley 1990
Subjects:
ferrous iron
soil
model
Online Access:https://hdl.handle.net/10568/166585
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author Kirk, G.J.D.
AHMAD, A.R.
NYE, P.H.
author_browse AHMAD, A.R.
Kirk, G.J.D.
NYE, P.H.
author_facet Kirk, G.J.D.
AHMAD, A.R.
NYE, P.H.
author_sort Kirk, G.J.D.
collection Repository of Agricultural Research Outputs (CGSpace)
description Kinetic equations are developed for a system in which a column of reduced soil is exposed to oxygen at one end. The equations are combined in a simulation model in which they are solved by finite‐difference methods. The model predicts the consequent diffusion of oxygen into the column; the diffusion of ferrous iron towards the oxidation zone; the rate of formation and concentration profile of the ferric hydroxide formed; and the diffusion by acid‐base transfer of the acidity produced in the oxidation reaction.A sensitivity analysis of the model, in which runs were made for a wide range of input parameters, showed that for most combinations of parameters, in water‐saturated soil, substantial amounts of iron are transferred towards the air‐exposed surface, leading to a well‐defined zone of ferric hydroxide accumulation. The profile of total iron in this zone is often banded. The pH in the zone falls by at least two units. A small amount of air‐filled pore space increases the depth of the oxidation front dramatically. The model indicates that coupled iron oxidation and diffusion reactions, which are very widespread in natural soils, may be understood quantitatively.
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publishDate 1990
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spelling CGSpace1665852025-05-14T10:39:58Z Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model Kirk, G.J.D. AHMAD, A.R. NYE, P.H. ferrous iron soil model Kinetic equations are developed for a system in which a column of reduced soil is exposed to oxygen at one end. The equations are combined in a simulation model in which they are solved by finite‐difference methods. The model predicts the consequent diffusion of oxygen into the column; the diffusion of ferrous iron towards the oxidation zone; the rate of formation and concentration profile of the ferric hydroxide formed; and the diffusion by acid‐base transfer of the acidity produced in the oxidation reaction.A sensitivity analysis of the model, in which runs were made for a wide range of input parameters, showed that for most combinations of parameters, in water‐saturated soil, substantial amounts of iron are transferred towards the air‐exposed surface, leading to a well‐defined zone of ferric hydroxide accumulation. The profile of total iron in this zone is often banded. The pH in the zone falls by at least two units. A small amount of air‐filled pore space increases the depth of the oxidation front dramatically. The model indicates that coupled iron oxidation and diffusion reactions, which are very widespread in natural soils, may be understood quantitatively. 1990-09 2024-12-19T12:56:27Z 2024-12-19T12:56:27Z Journal Article https://hdl.handle.net/10568/166585 en Wiley KIRK, G. J. D.; AHMAD, A. R. and NYE, P. H. 1990. Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model. Journal of Soil Science, Volume 41 no. 3 p. 411-431
spellingShingle ferrous iron
soil
model
Kirk, G.J.D.
AHMAD, A.R.
NYE, P.H.
Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model
title Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model
title_full Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model
title_fullStr Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model
title_full_unstemmed Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model
title_short Coupled Diffusion and Oxidation of Ferrous Iron in Soils. II. a Model of the Diffusion and Reaction of O*2, Fe*2+, H+ and Hco3 in Soils and a Sensitivity Analysis of the Model
title_sort coupled diffusion and oxidation of ferrous iron in soils ii a model of the diffusion and reaction of o 2 fe 2 h and hco3 in soils and a sensitivity analysis of the model
topic ferrous iron
soil
model
url https://hdl.handle.net/10568/166585
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AT ahmadar coupleddiffusionandoxidationofferrousironinsoilsiiamodelofthediffusionandreactionofo2fe2handhco3insoilsandasensitivityanalysisofthemodel
AT nyeph coupleddiffusionandoxidationofferrousironinsoilsiiamodelofthediffusionandreactionofo2fe2handhco3insoilsandasensitivityanalysisofthemodel

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