Characteristics of Silica Sorption and Solubility as Parameters to Evaluate the Surface Properties of Tropical Soils: I. The Index of Silica Reactivity

Abstract

Silica sorption by some Alfisols and Ultisols from southern Nigeria was studied. The percentage of silica lost from a solution brought into contact with a soil is called the index of silica reactivity (ISR).For reference samples, the scale of ISR follows the order kaolinite < < goethite < gibbsite. For soils where Iron oxides are the only sorbing phases, ISR is ruled by the part of the total specific surface area due to these oxides. More generally, however, ISR is sensitive to both the nature and the magnitude of the surface area so that soils rich in gibbsite exhibit higher ISR than the soils devoid of this mineral. To become useful as a comparative index, ISR should be amended so as to also take into account the specific reactivity of the different minerals with respect to soluble silica.

Ponto de efeito salino nulo de Latossolos da microbacia Chico Nunes, Mato Grosso

“…Os óxidos de Fe apresentam ponto de carga zero entre 7 e 9 (Schwertmann & Taylor, 1989), e os óxidos de Al, entre 8 e 9,2 (Hsu, 1989). Muitos autores têm observado relação direta entre os valores de PESN e a composição mineralógica da fração argila de horizontes subsuperficiais, e em solos oxídicos o valor do PESN é próximo ao valor do PCZ de óxidos de Fe e Al puros (Raij & Peech, 1972;Gallez et al, 1977), denotando semelhança entre o PCZ do mineral predominante da fração argila e o PESN do solo. Por isso, esta medida eletroquímica é utilizada muitas vezes como forma de avaliar o grau de intemperismo do solo e, conseqüentemente, do desenvolvimento pedológico, visando a sua aplicação à taxonomia dos solos.…”

A contemporary overview of silicon availability in agricultural soils

“…In contrast to P, as phosphate is held by soil colloids so strongly that it is highly immobile in soils, leaching of silicic acid from soils is a common phenomenon ( Sommer et al, 2006; Gérard et al, 2008; Frings et al, 2014). Although Gallez et al (1977) developed a method for measuring Si retention by soils (at pH 9.2) and Herbillon et al (1977) developed an “index of Si saturation” based on both the Si adsorption and Si release characteristics, these parameters have not met with wide acceptance. In acid soils, precipitation of added Si in form of hydroxyaluminosilicates (see below) might well be a more important sink for Si than adsorption to soil colloids.…”

Chemical and electrochemical properties of an Oxisol–Ultisol transition in the state of São Paulo, Brazil

“…Hendershot and Lavkulich (1978) and Peréz et al (1993) succeeded in the use of some electrochemical properties to assess pedogenic development in weathered soils. Gallez et al (1977) and Herbillon et al (1977) developed two indexes, based on silica solubility/adsorption, to describe pedogenetic environments resulting from processes of silication/ desilication, which have been recognized as important processes for the genesis of soils in the tropics (Curi and Franzmeier, 1984;Anjos et al, 1998;Schaefer et al, 2002).…”