Soil pore-water distributions and the temperature feedback of weathering in soils

Paul L. Richards, Lee Kump

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

A review of the literature suggests that large variations in pore-water chemistry exist within soils. The heterogeneity indicates that in soil microchemical environments, the chemistry of pore water evolves independently from one pore to another due to differences in surface area/volume ratios and water residence time. A plug-flow reactor model was developed to examine which size classes of pores contribute the most solute to water draining out of the soil profile, and to explore how temperature might affect a soil's ability to generate solute. The model is based on the simplification that soil pores can be approximated as a suite of capillaries of varying diameter. The model simulates each size class of pores as a plug-flow reactor with an unique water residence time and surface area.In the model, the pores which drain at the highest water contents have low surface area to water volume ratios and contribute relatively little to the overall solute flux from a soil. The smallest pores that drain at the lowest water contents were found to have the highest surface area to volume ratios and contribute the most solute. The calculations also suggest that activation energy and water viscosity have competing effects on the temperature dependence of weathering. As the temperature increases, the dissolution rate constant increases and smaller pores drain; however, water residence time decreases. This decrease in the water residence time is due to decreasing water viscosity, which can be incorporated into the dissolution rate law for quartz with an activation energy of approximately -15 kJ/mole. Studies that parameterize the temperature dependence of weathering using the Arrhenius approach can account for this effect by reducing the predicted activation energy by an appropriate value.

Original languageEnglish (US)
Pages (from-to)3803-3815
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume67
Issue number20
DOIs
StatePublished - Oct 15 2003

Fingerprint

Weathering
porewater
weathering
soil water
Feedback
Soils
Water
solute
residence time
soil
surface area
temperature
activation energy
drain
water
Temperature
Activation energy
viscosity
water content
Water content

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

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title = "Soil pore-water distributions and the temperature feedback of weathering in soils",
abstract = "A review of the literature suggests that large variations in pore-water chemistry exist within soils. The heterogeneity indicates that in soil microchemical environments, the chemistry of pore water evolves independently from one pore to another due to differences in surface area/volume ratios and water residence time. A plug-flow reactor model was developed to examine which size classes of pores contribute the most solute to water draining out of the soil profile, and to explore how temperature might affect a soil's ability to generate solute. The model is based on the simplification that soil pores can be approximated as a suite of capillaries of varying diameter. The model simulates each size class of pores as a plug-flow reactor with an unique water residence time and surface area.In the model, the pores which drain at the highest water contents have low surface area to water volume ratios and contribute relatively little to the overall solute flux from a soil. The smallest pores that drain at the lowest water contents were found to have the highest surface area to volume ratios and contribute the most solute. The calculations also suggest that activation energy and water viscosity have competing effects on the temperature dependence of weathering. As the temperature increases, the dissolution rate constant increases and smaller pores drain; however, water residence time decreases. This decrease in the water residence time is due to decreasing water viscosity, which can be incorporated into the dissolution rate law for quartz with an activation energy of approximately -15 kJ/mole. Studies that parameterize the temperature dependence of weathering using the Arrhenius approach can account for this effect by reducing the predicted activation energy by an appropriate value.",
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Soil pore-water distributions and the temperature feedback of weathering in soils. / Richards, Paul L.; Kump, Lee.

In: Geochimica et Cosmochimica Acta, Vol. 67, No. 20, 15.10.2003, p. 3803-3815.

Research output: Contribution to journalArticle

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