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Title: PREDICTING TRACE ELEMENT ADSORPTION BY SOILS USING SOIL CHEMICAL PARAMETERS

Author
item Goldberg, Sabine
item LESCH, S - UC RIVERSIDE, CA
item Suarez, Donald

Submitted to: Proceedings of the International Salinity Forum
Publication Type: Proceedings
Publication Acceptance Date: 4/11/2005
Publication Date: 4/25/2005
Citation: Goldberg, S.R., Lesch, S.M., Suarez, D.L. 2005. Predicting trace element adsorption by soils using soil chemical parameters. In: Proceedings of the International Salinity Forum, Managing Saline Soils and Water: Science, Technology, and Soil Issues. April 25-27, 2005. Riverside, CA pp:197-200.

Interpretive Summary: Boron is a required element for plant growth that is toxic at high concentration. Molybdenum is required by plants and toxic to animals at higher concentrations. Arsenic is toxic to animals at higher concentrations. A better understanding of the adsorption behavior of these elements is necessary. Adsorption of boron, molybdenum, and arsenate by a large set of soils was investigated under changing conditions of solution pH. The adsorption behavior was evaluated and predicted using a chemical model and easily measured soil chemical characteristics. Our results will benefit scientists who are developing models of boron, molybdenum, and arsenic movement in arid zone soils. The results can be used to improve predictions of the behavior of these elements and thus aid action and regulatory agencies in the management of soils and waters which them in contain elevated concentrations.

Technical Abstract: The constant capacitance model, a chemical surface complexation model, was applied to boron, molybdenum, and arsenate, As(V), adsorption on up to 49 soils selected for variation in soil properties. The constant capacitance model was able to fit boron, molybdenum, and arsenate adsorption on all soils. General regression models were developed for predicting soil B, Mo, and As(V) surface complexation constants from easily measured soil chemical characteristics. These chemical properties were cation exchange capacity, inorganic carbon content, organic carbon content, aluminum oxide content, iron oxide content, and surface area. The prediction equations were used to obtain values for the B, Mo, and As(V) surface complexation constants for additional soils, thereby providing a completely independent evaluation of the ability of the constant capacitance model to describe adsorption. Incorporation of these prediction equations into chemical speciation-transport models will allow simulation of soil solution B, MO, and As(V) concentrations under diverse agricultural and environmental conditions without the requirement of soil specific adsorption data and subsequent parameter optimization.