Hygroscopic water content as an indicator of soil dispersity: thermodynamic basis and experimental verifi cation

Abstract

The adsorption properties of dispersed systems are determined by their surface energy, therefore the indicators of hygroscopy (adsorbed water content) and dispersity (specific surface area of the solid phase) of soils and sediments are in close mutual correlation. This well-known empirical fact received a new fundamental interpretation based on the theory of disjoining water pressure according to Deryagin in the form of a thermodynamic equation connecting the specific surface area, hygroscopic water content of soil samples and the relative humidity of the air in the laboratory room. The theoretical equation allowed us to substantiate the methodology for quantifying the hydrophilic specific surface area of soil samples based on widespread data on their hygroscopy. A comparison of the new method with the standard BET-analysis of the specific surface area, as well as with the previously proposed physically based method for its determining by the slope of thermodynamic water retention curves, showed their statistically reliable agreement in a wide range of estimated specific surface area values from 5 to 340 m²×g^-1 for soil samples of different genesis and texture.

References

1. Вадюнина А.Ф., Корчагина З.А. Методы исследования физических свойств почв и грунтов. М., 1973. 2. Воронин А.Д. Основы физики почв. М., 1986. 3. Колоскова А.В., Гилязова С.М. Поверхностные свойства основных типов почв ТАССР и их высокодисперсных фракций // Почвоведение. 1977. № 5. 4. Роде А.А. Избранные труды. Т. 3. Основы учения о почвенной влаге. М., 2008. 5. Судницын И.И. Новые методы оценки водно-физических свойств почв и влагообеспеченности леса. М., 1966. 6. Щукин Е.Д., Перцов А.В., Амелина Е.А. Коллоидная химия. М., 1982. 7. Arthur E., Tulle M., Moldrup P. et al. Soil specific surface area and non-singularity of soil-water retention at low saturations // Soil Sci. Soc. of Am. J. 2013. Vol. 77. https://doi.org/10.2136/sssaj2012.0262 8. Arthur E., Tuller M., Moldrup P. et al. Evaluation of a fully automated analyzer for rapid measurement of water vapor sorption isotherms for applications in soil science // Soil Sci. Soc. Am. J. 2014. Vol. 78. https://doi.org/10.2136/sssaj2013.11.0481n 9. Campbell G.S.; Shiozawa S. Prediction of hydraulic properties of soils using particle-size distribution and bulk density data // Eds. van Genuchten M.Th. et al. Proceedings of the International Workshop on Indirect Methods for Estimating the Hydraulic Properties of Unsaturated Soils. 1994. University of California, Riverside, CA. 10. Carotenuto A., Dell'Isola M. An experimental verification of saturated salt solution-based humidity fixed points // Int. J. Thermophys. 1996. Vol. 17(6). https://doi.org/10.1007/BF01438677 11. Gregg S.J., Sing K.S.W. Adsorption, Surface Area and Porosity, 2nd ed. San Diego, USA, 1982. 12. ISO 9277:2022. Determination of the specific surface area of solids by gas adsorption — BET method. Available online: https://www.iso.org/standard/71014.html (accessed on 13 Sept. 2023). 13. Resurreccion A.C., Moldrup P., Tuller M. et al. Relationship between specific surface area and the dry end of the water retention curve for soils with varying clay and organic carbon contents // Water Resour. Res. 2011. Vol. 47. https://doi.org/10.1029/2010WR010229 14. Schneider M., Goss K.U. Prediction of the water sorption isotherm in air dry soils // Geoderma. 2012. Vol. 170. http://doi.org/10.1016/j.geoderma.2011.10.008 15. Sing K. The use of nitrogen adsorption for the characterization of porous materials // Colloids and Surfaces A: Physicochem. Eng. Aspects. 2001. Vol. 187–188. https://doi.org/10.1016/S0927-7757(01)00612-4 16. Smagin A.V. Physically based mathematical models of the water vapor sorption by soils // Eurasian Soil Science. 2011. Vol. 44 (6). https://doi.org/10.1134/S1064229311060135 17. Smagin A.V. Thermogravimetric determination of specific surface area for soil colloids. Colloid J. 2016. Vol. 78. https://doi.org/10.1134/S1061933X16030170. 18. Smagin A.V. About thermodynamic theory of water retention capacity and dispersity of soils // Eurasian Soil Science. 2018. Vol. 51(7). https://doi.org/10.1134/S1064229318070098 19. Terzaghi K., Peck R. Soil Mechanics in Engineering Practice. New York, 1948. 20. Wuddivira M.N., Robinson D.A., Lebron I. et al. Estimation of soil clay content from hygroscopic water content measurements // Soil Sci. Soc. Am. J. 2012. Vol. 76(5). https://doi.org/10.2136/sssaj2012.0034 21. Yan F., Tuller M., de Jonge L.W. et al. Specific surface area of soils with different clay mineralogy can be estimated from a single hygroscopic water content // Geoderma. 2023. Vol. 438. https://doi.org/10.1016/j.geoderma.2023.116614