Effects of soil physical and chemical characteristics on adsorption of leached CCA and ACQ preservative components

IRG/WP 03-50200

S Stefanovic, P A Cooper

The objective of this study was to examine the effect of soil characteristics on adsorption of wood preservative components from CCA and ACQ preservative systems. Adsorption of leached CCA and ACQ preservative components in soils with different characteristics were studied. Three soils (clay, sandy and organic) were investigated using different concentrations of leach water of CCA and ACQ wood preservatives made in the lab by extended leaching of treated sawdust. Samples of soil and leach water were equilibrated with shaking for 2 to 48 h at 22oC. Attempts were made to model adsorption results using the Langmuir adsorption isotherm. Supernatants of seven additional soils were sampled for one leachate concentration and after 48 h mixing. All soils were analyzed for content of clay, silt and sand (soil texture), organic matter, pH, CEC, concentration of Al, Mn, and Fe oxides. Multiple regression analysis was used to relate soil variables to the adsorption of CCA preservative components after 48 h of shaking for all ten soils, but there were no clear correlation. Arsenic adsorption in the clay soil was variable but appeared to be still increasing in the clay and organic soils after 48 hours exposure. The sandy soil stabilized at a relatively low amounts of all components. Adsorption of As, Cu and Cr showed high or moderately high correlation with concentration of equilibrating solution. An adsorption constant was not reached with this experiment because concentration of As, Cu and Cr in leachates were low. Consequently, adsorption of preservatives components did not follow the Langmuir isotherms. Adsorption characteristics at these low concentrations were not statistically related to the soil characteristics.

Keywords: Adsorption, soil characteristics, CCA, ACQ

Conference: 03-05-18/23 Brisbane, Australia

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