THE EQUILIBRIUM OF CLAY MINERALS WITH AQUEOUS SOLUTIONS IN SOILS
V.N. Shoba and K.V. Chudnenko*
Siberian Research Institute of Soil Management and Chemicalization of Agriculture, Siberian Federal AgroBioTech Scientific Center,
Russian Academy of Sciences, Krasnoobsk, 630501, Russia
*A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1A, Irkutsk, 664033, Russia
Keywords: Physicochemical modeling, soils, fine colloids, clay minerals, humic acids, end-members, chemical po-tentials, activity coefficients
Abstract
We studied the total chemical and mineralogical compositions of fine colloids (fraction <0.08 μm) in the upper horizons of contrasting soil compositions and properties. Based on the analytical data, the crystallochemi-cal formulas of clay minerals with a 2:1 structure are calculated, and the chemical potentials of independent com-ponents and the activity coefficients of the main end-members are determined. Using the Selector software, the equilibrium phase–multicomponent composition of soils is calculated, and the similarity and difference in the crystal chemistry of 2:1 clay minerals produced by two different methods are shown. The calculated Gibbs ener-gy values of these minerals are close to the calorimetric data for smectites. It is shown that the contents of typical elements in 2:1 clay minerals reflect the genetic properties of soils. In soils of alkaline series (Solonetz), such minerals are relatively enriched in sodium and magnesium; in soils of acidic series (Podzoluvisols and Cambi-sols), in hydrogen and iron; and in soils of the neutral series (Chernozems, Arenosols, and Umbric Gleysols), in calcium.
DOI: 10.15372/RGG2019035
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