Abstract
Usually, equilibrium constants for aqueous geochemical reactions in the unsaturated zone are assumed to be equal to those for free water solutions (at atmospheric pressure) considered in classical water chemistry. This paper shows that high negative pressures in pore water may essentially change these constants in dry soils and sediments.
The influence of negative capillary pressures on equilibrium constants for some important reactions occurring in the upper part of the unsaturated zone is analyzed. It is shown that values of these constants at low water contents may differ from those normally used by orders of magnitude. Sediment drying usually decreases the equilibrium constant for salt dissolution-precipitation reactions (makes precipitation easier) and for silicate weathering (delays it), whilst in the case of dedolomitization, orthoclase-albite transition and some types of cation exchange the equilibrium constant grows and these processes in dry soils and sediments have to be enhanced.
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References
Bignell, N. (1984) Partial molar volumes of atmospheric gases in water. Journ. Phys. Chem. 88, 5409-5412
Bruton, C. J. and Viani, B. E. (1992) Geochemical modeling of water-rock interactions in the unsaturated zone. In Water-Rock Interaction (eds. Y. K. Kharaka and A. S. Maest), pp. 705-708. Balkema, Rotterdam.
Burt, T. P., Heathwaite, A. L. and Trudgill, S. T. (ed.) (1993) Nitrate: Processes, Patterns and Management. John Wiley & Sons, Chichester.
Clark, S. P. (ed.) (1966) Handbook of Physical Constants. Amer. Geol. Soc., N. Y.
Carmichael, R. S. (ed.) (1990) Practical Handbook of Physical Properties of Rocks and Minerals. CRC Press, N.Y.
Derjaguin, B. V. and Churaev, N. V. (1974) Structural component of disjoining pressure. J. Colloid Interface Sci. 49, 249-255.
Friedman, G. M. and Sanders, J. E. (1967) Origin and occurrence of dolostones. In Developments in Sedimentology (eds. G. V. Chilingar et al.), Vol. 9A, pp. 267-348. Elsevier, Amsterdam.
Grundmann, G. L., Renault, P, Rosso, L and Bardin, R. (1995) Differential effects of soil water content and temperature on nitrification and airation. Soil Sci. Soc. Amer. J. 59, 1342-1349.
Johnson, J. W., Oelkers, E. H. and Helgeson, H. C. (1992) SUPCRT92: A software package for calculating the standard molar thermodynamic properties of minerals, gases, aqueous species, and reactions from 1 to 5000 bars and 0° to 1000°C. Computers and Geosciences 18, 899-947.
Klute, A. (ed.) (1986) Methods of soil analysis. Part 1. 2nd edn. Agron. Monogr., Vol. 9. ASA and SSSA, Madison, WI.
Krumgaltz, B. S., Pogorelsky, R. and Pitzer, K. S. (1996) Volumetric properties of single aqueous electrolytes from zero to saturation concentration at 298.15 °K represented by Pitzer's ion-interaction equations. J. Phys. Chem. Ref. Data 25(2), 663-689.
Lindsay, W. (1979) Chemical Equilibria in Soils. John Wiley & Sons, N.Y.
Lown, D. A., Thirsk, H. R. and Wynne-Jones L. (1968) Effect of pressures on ionization equilibria in water at 25 °C. Trans. Faraday Soc. 64, 2073-2080.
Mattigod, S. V. and Kittrick, J. A. (1980) Temperature and water activity as variables in soil mineral activity diagrams. Soil Sci. Soc. Am. J. 44, 149-154.
Mercury, L. and Tardy, Y. (1997) Caracteristiques physicochimiques de l'eau capillaire et des gouttelettes de brouillard C.R. Acad. Sci. Paris 324, Ser. IIa, 863-873
Michurin, B. N. and Onischenko, V. G. (1971) Change of pore-water pressure with the thickness of the absorbed water film. In Proceeding of the Agro-physical Institute, Leningrad 32, 67-71 (In Russian).
Millero, F. J. (1982) The effect of pressure on the solubility of minerals in water and seawater. Geochimica et Cosmochimica Acta 46, 11-22.
Moore, J. C., Battino, R., Rettich, T. R., Handa, Y. P. and Wilhelm, E. (1982) Partial molar volumes of “gases” at infinite dilution in water at 298.15 K. J. Chem. Eng. Data 27, 22-24.
Morel, F. M. M. (1983) Principles of Aquatic Chemistry. Wiley-Intersci. Publ., N.Y.
Owen, B. B. and Brinkley, S. R. (1941) Calculation of the effect of pressure upon ionic equilibrium in pure water and in salt solutions. Chem. Rev. 42, 461-474.
Sha-Qingan, Pan-Zhengpu and Wang-Yao (1979) Recent dedolomitization in the vadose zone. Scientica Geologica Sinica 4, 378-383.
Shock, E. L and Helgeson H. C. (1982) Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000 °C. Geochimica et Cosmochimica Acta 52, 2009-2036.
Stumm, W. and Morgan, J. J. (1996) Aquatic Chemistry. Wiley-Intersci. Publ., N.Y.
Tan, Kim H. (1994) Environmental Soil Science. Marcel Dekker, Inc., N.Y.
Tardy, Y. and Touret, O. (1987) Hydration energies of smectites: a model for glauconite, illite, and corrensite formation. In: Proc. of the Intern. Clay Conf., Denver, 1985 (eds. L. G. Schultz, A. Van Olphen and F. A. Mumpton), pp. 46-52. The Clay Minerals Society, Bloomington, Indiana.
Weast R. C. (1965) Handbook of Chemistry and Physics. The Chemical Rubber Co., Cleveland.
Zilberbrand, M. (1997) A nonelectrical mechanism of ion exclusion in thin water films in finely dispersed media. Journ. of Colloid and Interface Science 192(2), 471-474.
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Zilberbrand, M. On Equilibrium Constants for Aqueous Geochemical Reactions in Water Unsaturated Soils and Sediments. Aquatic Geochemistry 5, 195–206 (1999). https://doi.org/10.1023/A:1009695510370
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DOI: https://doi.org/10.1023/A:1009695510370