Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2008
Publication Date: 11/30/2008
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2207.pdf
Citation: Goldberg, S.R., Hyun, S., Lee, L.S. 2008. Chemical modeling of Arsenic(III, V) and Selenium(IV, VI) adsorption by soils surrounding ash disposal facilities. Vadose Zone Journal. 7(4):1231-1238. Interpretive Summary: Arsenic and selenium are trace elements that are toxic to animals 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 arsenate, arsenite, selenate, and selenite by 16 soil samples surrounding ash disposal facilities was investigated under changing conditions of solution ion concentration. The adsorption behavior was evaluated and described using a chemical surface complexation model. Our results will benefit scientists who are developing models of arsenic and selenium movement in soils. The results can be used to improve predictions of arsenic and selenium behavior in soils and thus aid action and regulatory agencies in the management of soils which contain elevated concentrations of arsenic and selenium.
Technical Abstract: Leachate derived from coal ash disposal facilities is a potential anthropogenic source of arsenic and selenium to the environment. To establish a practical framework for predicting attenuation and transport of As and Se in ash leachates, the adsorption of As(III), As(V), Se(IV), and Se(VI) had been characterized in prior studies (Burns et al., 2006; Hyun et al., 2006) for 18 soils obtained down-gradient from ash landfill sites and representing a wide range of soil properties. The constant capacitance model was able to describe adsorption of these ions on all soils as a function of solution ion concentration by optimizing only one adjustable parameter, the anion surface complexation constant. This chemical model represents an advancement over adsorption isotherm equation approaches which contain two empirical adjustable parameters. Incorporation of these anion surface complexation constants into chemical speciation transport models will allow simulation of soil solution anion concentrations under diverse environmental and agricultural conditions.