The effect of land plants on weathering rates of silicate minerals

Journal Article · Sun May 01 00:00:00 EDT 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90013-2· OSTI ID:7064832

Drever, J I ^[1]

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1. Univ. of Wyoming, Laramie, WY (United States)

Land plants and their associated microbiota directly affect silicate mineral weathering in several ways: by generation of chelating ligands, by modifying pH through production of CO[sub 2] or organic acids, and by altering the physical properties of a soil, particularly the exposed surface areas of minerals and the residence time of water. In laboratory experiments far from equilibrium, 1 mM oxalate (a strong chelator of Al) has a negligible effect on the dissolution rate of alkali feldspars, but some effect on calcic feldspars and olivine. By analogy to oxalate, the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small, except perhaps in microenvironments adjacent to roots and fungal hyphae. The effect of pH on silicate mineral dissolution rate depends on pH: below pH 4-5, the rate increases with decreasing pH, in the circumneutral region the rate is pH-independent, and at pH values above around 8 the rate increases with increasing pH. Vegetation should thus cause an increase in weathering rate through the pH effect only where the pH is below 4-5. As an overall generalization, the effect of plants on weathering rate through changes in soil-solution chemistry is probably small for granitic rocks; it may be greater for more mafic rocks. It is the release of Ca and Mg from mafic rocks that has the greatest influence on the global CO[sub 2] budget.

• OSTI ID: 7064832
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 58:10; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
EARTH PLANET
CARBON CYCLE
SILICATE MINERALS
WEATHERING
ALUMINIUM
CALCIUM
CARBON DIOXIDE
MAGNESIUM
ALKALINE EARTH METALS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ELEMENTS
METALS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PLANETS
540210* - Environment
Terrestrial- Basic Studies- (1990-)