The effect of an exchanger phase, carbon dioxide, and mineralogy on the rate of geochemical weathering

Miscellaneous · Sun Jan 01 00:00:00 EST 1984

OSTI ID:7189098

Amrhein, C

The dissolution (weathering) of soil minerals can have an appreciable effect on soil water chemistry. The rate at which mineral dissolution in water approaches equilibrium is dependent upon the type of minerals present, the surface area/solution volume ratio, the ionic composition of the solution, the nature of the exchanger phase of the soil, the temperature and the local partial pressure of carbon dioxide. Geochemical weathering has an important effect on the processes relating to sodic soil reclamation, nutrient availability, soil genesis, management of overburden materials from mining activities, and salt loading to surface and ground waters. Research was conducted to determine, quantitatively, the effects of CO{sub 2} and exchanger phase composition on the kinetics of calcium mineral dissolution. It was found that the presence of exchangeable sodium greatly increased the initial rate of mineral dissolution by acting to keep the soil solution low in Ca{sup 2+} ions. The kinetics of calcite dissolution were controlled by the gas transfer reaction, CO{sub 2}(gas) {yields} CO{sub 2}(ag), at CO{sub 2} levels below .03 atmospheres. A mechanistic kinetic model was proposed that included the CO{sub 2} reaction kinetics and an adsorption/hydration reaction with the calcite surface. In general, mineral weathering was found to rarely obey a diffusion controlled model and was better described by mechanistic kinetics invoking elementary chemical reactions. In addition, it was found that the weathering rate of anorthite (a calcium silicate) was too slow to contribute significant amounts of Ca{sup 2+} ions to the soil solution and the phenomenon of calcite supersaturation commonly found in soil solutions is attributed to carbon dioxide dynamics.

• Research Organization: Utah State Univ., Logan, UT (USA)
• OSTI ID: 7189098
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALCIUM SILICATES
CHEMICAL REACTION KINETICS
GEOCHEMISTRY
MATHEMATICAL MODELS
SOILS
WEATHERING
CARBON DIOXIDE
LAND RECLAMATION
MINERALOGY
OVERBURDEN
SOIL CHEMISTRY
WATER CHEMISTRY
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMISTRY
KINETICS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SILICATES
SILICON COMPOUNDS
580000* - Geosciences