Some Factors Affecting the Adsorption of Sulfate by Alabama Soils

Abstract

The sulfate content of a number of Alabama Soils was determined by extracting with various solutions. The sulfate extracted was measured turbidimetrically. Some factors affecting the adsorption of sulfate by soils were studied. About the same amount of sulfate was extracted by neutral sodium acetate solution, sodium acetate buffered at pH 4.8, KH2PO4 solution containing 100 ppm. phosphorus, and KH2PO4 solution containing 500 ppm. phosphorus. However, 0.1 N HCl solution extracted little or no sulfate. The samples contained only small quantities of water‐soluble sulfate except where sulfate had been recently applied. The results show that sulfate is retained to a certain extent by most soils. The subsurface layers usually contain more sulfate and are capable of adsorbing more sulfate than the surface layers. The surface layers of most of the light textured soils did not contain sulfate or show a capacity to adsorb sulfate from solution. The capacity of soils to adsorb sulfate is affected by certain soil treatments. Increasing amounts of superphosphate applied to a Cecil sandy clay loam resulted in decreasing amounts of soluble sulfate. The data show that superphosphate decreased the capacity of this soil to adsorb sulfate from a CaSO4 solution. Liming also resulted in a decrease in the retention of sulfate. The sulfate adsorption capacity of a number of materials was determined in an attempt to show what fractions of soils may be responsible for the retention of sulfate. The data show that dehydrated Al2O3 adsorbed much more sulfate than any of the other materials. The iron minerals adsorbed rather small amounts of the sulfate while the Davidson colloid, kaolinite, and bauxite were intermediate.

Metal-Induced Sulfate Adsorption by Soils

“…The adsorbed SO^^' fraction can be extracted from soils by a variety of extractants. These include Ca(H2P04)2 (Fox et al, 1964), KHgPO^ (Ensminger, 1954), Ca(0H)2 and CaCOg suspensions (Williams and Steinberg, 1962), NaHCOg (Kilmer and Nearpass, 1960), neutral 1 N NH4OAC (McClung et al, 1959), acid NH^OAc (Bardsley and Lancaster, 1960;Sanford and Lancaster, 1962), and Morgan's solution (Chesnin and Yien, 1950). Fox et al (1964) found Ca(H2P04)2 to be preferable to KH2PO4 because, while it gave values similar to KH2PO4, it also produced extracts essentially free of colloidal material which is often a problem with KH2PO4.…”

A study of the pattern of sulphur responses shown by dryland lucerne on some brown-grey earths

“…P adjusted to pH 6.5) as recommended by Ensminger (1954 Sulphate soluble in 0.15% CaCl 2 after heat treatment ("heat-treated" soluble sulphate) is that fraction representing easily mineralisable sulphur and is measured by determining the soluble sulphate present after pre-treatment of the moist soil on a hot-water bath (Williams and Steinbergs 1959).…”

Resposta de culturas e disponibilidade de enxofre em solos com diferentes teores de argila e matéria orgânica submetidos à adubação sulfatada

“…No entanto, a disponibilidade imediata do S é controlada pelo processo de adsorção/dessorção do sulfato, por meio do equilíbrio rápido entre aquele que está na solução e aquele da fase sólida do solo. A adsorção do sulfato depende principalmente dos teores e dos tipos de argilominerais e de óxidos presentes no solo, e os grupos funcionais das arestas quebradas da caulinita e aqueles da superfície dos óxidos de ferro são os que possuem maior capacidade de reter esse íon (Ensminger, 1954;Peak et al, 1999). O pH do solo, por sua vez, interfere na energia de ligação dos grupos funcionais aos cátions metálicos estruturais dos argilominerais e óxidos do solo, e seu aumento causa sua desprotonação, dificultando e até impedindo a adsorção de sulfato (Mehlich, 1964;Parfitt e Smartt, 1978;Peak et al, 1999;Casagrande et al, 2003;Goldberg, 2010).…”