HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gebhardt, H. Articles by Coleman, N. T. Search for Related Content PubMed Articles by Gebhardt, H. Articles by Coleman, N. T. Agricola Articles by Gebhardt, H. Articles by Coleman, N. T.

Anion Adsorption by Allophanic Tropical Soils: I. Chloride Adsorption¹

ABSTRACT

The adsorption of Cl by Andepts from Mexico, Colombia, and Hawaii was measured in solutions of HCl, HCl + NaCl, and AlCl₃. Chloride adsorption varied from 0-8 meq/100 g at pH 6 to as much as 32 meq/100 g at pH 3.8. At given pH, adsorption was concentration-dependent in a manner consistent with the Langmuir adsorption equation. For a B-horizon sample from San Gregorio, Mexico, the Cl adsorption maxima, in meq/100 g, were 7.4 at pH 6; 10.7 at pH 4.8; 13.4 at pH 4.4; 17.3 at pH 4.2; and 31.6 at pH < 4. The average a from the Langmuir equation was 0.04 liter/meq. Adsorbed Cl was removed by leaching with water, and was exchanged by NO₃.

Chloride adsorption from HCl or HCl-NaCl was accompanied by the consumption of protons; adsorption from AlCl₃ resulted in the hydrolysis and precipitation of Al. Protons consumed or Al hydrolyzed exceeded Cl adsorbed by amounts corresponding closely to the effective CEC. The results suggest that protons are adsorbed to produce positively charged sites, which bind Cl nonspecifically.

Chloride adsorption capacity can be conveniently measured by shaking soil with AlCl₃ solution and measuring Cl uptake. Chloride capacities of soils and clay minerals, determined by the AlCl₃ procedure, were, in meq/100 g, 7–30 for Dystrandepts; 16–18 for Hydrandepts; 2–4 for acid soils containing crystalline clay and oxide minerals; 4 for kaolinite; zero for montmorillonite and illite.

¹ Contribution from the Dep. of Soil Science and Agr. Eng., Univ. of California, Riverside 92502. Support from the National Science Foundation, under Research Grant NSF-GB-11711-(Pratt), is gratefully acknowledged.

² Postgraduate Research Soil Scientist and Professor, respectively, Dep. of Soil Science and Agr. Eng., Univ. of California 92502.

Received for publication September 10, 1973. Accepted for publication September 17, 1973.