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United States Department of Agriculture

Agricultural Research Service

Title: Influence of Anion Competition on Boron Adsorption by Clays and Soils

Authors
item Goldberg, Sabine
item Forster, Harold
item Lesch, Scott - UCR, RIVERSIDE
item Heick, E - UCR, RIVERSIDE

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 30, 1995
Publication Date: N/A

Interpretive Summary: Boron is a specifically adsorbing anion that is toxic to plants at elevated concentrations. Toxic concentrations can occur in agricultural soils and irrigation waters. A better understanding of the adsorption behavior of this ion is necessary. Adsorption of boron by clay minerals and soils was investigated under changing conditions of solution pH and competing anion concentration. Our results show little competitive effect on boron adsorption even by the strongly adsorbing anion, phosphate. Our results will benefit scientists who are developing models of boron movement in arid zone soils. The results can be used to improve predictions of boron behavior in soils and thus aid action and regulatory agencies in the management of soils and waters of arid areas which contain elevated concentrations of boron.

Technical Abstract: Boron adsorption on the clay minerals, kaolinite and montmorillonite, and two arid zone soils was investigated as a function of solution pH (3-12) and presence of competing anions (nitrate, sulfate, molybdate, and phosphate) after 2 hours of reaction time. Boron adsorption on all materials increased from pH 3 to 8 and decreased from pH 10 to 12.. Boron adsorption was greatest using a NaNO3 background electrolyte. The competitive anion effects on B adsorption increased in the order: sulfate < molybdate < phosphate. The competitive effect on B adsorption was small even for the strongly adsorbing anion, phosphate. Our results suggest that B adsorbing sites are for the most part specific to B and act independent of competing anions. This result will simplify the description of B transport in that changes in solution concentration of competing anions may not have to be considered.

Last Modified: 11/26/2014
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