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Title: Arsenate adsorption by unsaturated alluvial sediments

item Goldberg, Sabine
item Suarez, Donald

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2013
Publication Date: 4/30/2013
Citation: Goldberg, S.R., Suarez, D.L. 2013. Arsenate adsorption by unsaturated alluvial sediments. Soil Science Society of America Journal. 77(3):782-791.

Interpretive Summary: Arsenic is a trace element that is toxic to animals at elevated concentrations. Toxic concentrations of arsenic species can occur in soils, groundwaters, and sediments. A better understanding of the adsorption behavior of arsenic species is necessary. Adsorption of arsenic by five sediments from the Antelope Valley, Mohave Desert, California was investigated under changing conditions of solution pH and solution arsenic concentration. The adsorption behavior of arsenic was evaluated and described using a chemical surface complexation model. Our results will benefit scientists who are developing models of arsenic movement in sediments and soils. The results can be used to improve predictions of arsenic behavior in sediments and soils and thus aid action and regulatory agencies in the management of sediments, soils, and groundwaters which contain elevated concentrations of arsenic species.

Technical Abstract: Arsenate adsorption as a function of solution arsenic concentration and solution pH was investigated on five alluvial sediments from the Antelope Valley, Western Mojave Desert, California. Arsenate adsorption increased with increasing solution pH, exhibited a maximum around pH 4 to 5, and then decreased with increasing pH. The constant capacitance model was able to fit arsenate adsorption on the sediments as a function of solution arsenic concentration and solution pH. A general regression model was used to predict arsenate surface complexation constants from routinely measured chemical parameters. The predicted arsenate constants were used to predict adsorption on the sediments, thereby providing a completely independent evaluation of the ability of the model to describe arsenate adsorption. The prediction equations were able to satisfactorily predict arsenate adsorption on one of the five sediments whose chemical properties fell into the range for the set of soils used to develop the prediction equations. Equimolar phosphate concentrations did not affect the extent of arsenate adsorption indicating that the extent of arsenate remediation by the sediments will be unaffected by the low amounts of native phosphate.