Adsorbed ion activity coefficients in K-Ca exchange on soil fractions derived from volcanic materials

Escudey, M.; Díaz P; Foerster J.E.; Galindo, G.

Keywords: iron, soil, oxide, andisol, exchange, volcanic, cation, material, allophanic

Abstract

The effects of temperature and iron oxide coatings on the adsorbed ion activity coefficients obtained by the Gaines-Thomas treatment for the K-Ca exchange equilibria on clay fractions of 3 Chilean Andisols were studied. The comparison with the values calculated through the Vanselow approach, using conversion equations, was also considered. Adsorbed Ca activity coefficient curves present a similar shape for the Gaines-Thomas and Vanselow approaches; for K, maxima were observed only when the Gaines-Thomas treatment was used. Iron oxide coated samples showed higher adsorbed ion activity coefficients than allophanic samples. The adsorbed K activity coefficients increased when temperature increased from 4°C to 26.5°C, but only a slight effect on Ca ions was observed. In both types of samples, the presence of 3 possible selective sites was detected: K-selective sites, Ca-selective sites, and sites where K-Ca competition occurs.

Más información

Título de la Revista: AUSTRALIAN JOURNAL OF SOIL RESEARCH
Volumen: 35
Número: 1
Editorial: PERGAMON-ELSEVIER SCIENCE LTD
Fecha de publicación: 1997
Página de inicio: 123
Página final: 130
URL: http://www.scopus.com/inward/record.url?eid=2-s2.0-0030619507&partnerID=q2rCbXpz