Influence of Soil Geochemical and Physical Properties on the Sorption and Bioaccessibility of Chromium(III)

Abstract

There are numerous Cr(III)-contaminated sites on Department of Defense (DoD) and Department of Energy (DOE) lands that are awaiting possible clean up and closure. Ingestion of contaminated soil by children is the risk driver that generally motivates the likelihood of site remediation. The purpose of this study was to develop a simple statistical model based on common soil properties to estimate the hioaccessibility of Cr(III)-contaminated soil upon ingestion. Thirty-five uncontaminated soils from seven major soil orders, whose properties were similar to numerous U.S. DoD contaminated sites, were treated with Cr(III) and aged. Statistical analysis revealed that Cr(III) sorption (e.g., adsorption and surface precipitation) by the soils was strongly correlated with the clay content, total inorganic C, pH, and the cation exchange capacity of the soils. Soils with higher quantities of clay, inorganic C (i.e., carbonates), higher pH, and higher cation exchange capacity generally sequestered more Cr(III). The amount of Cr(III) bioaccessible from the treated soils was determined with a physiologically based extraction test (PBET) that was designed to simulate the digestive process of the stomach. The bioaccessibility of Cr(III) varied widely as a function of soil type with most soils limiting bioaccessibility to <45 and <30% after I and 100 d soil-Cr aging, respectively. Statistical analysis showed the bioaccessibility of Cr(III) on soil was again related to the clay and total inorganic carbon (TIC) content of the soil. Bioaccessibility decreased as the soil TIC content increased and as the clay content decreased. The model yielded an equation based on common soil properties that could be used to predict the Cr(III) bioaccessibility in soils with a reasonable level of confidence.

Effects of low-molecular-weight organic acids and residence time on desorption of Cu, Cd, and Pb from soils

“…Lower organic matter content of soil also favored desorption of metals from soils. The higher soil CEC generally coexisted with higher content of clay and organic matter, and showed strong ability on the sequestration of metals (Stewart et al, 2003) and vice verse. Another soil property that may be responsible for this effect was manganese oxide, the content of which in Heilongjiang soil was an order of magnitude higher than that of Jiangxi soil.…”

Soil humic acids may favour the persistence of hexavalent chromium in soil

“…adsorption and surface precipitation) onto soil colloids, a mechanism strongly related to their peculiarities, such as the clay-oxideshydroxides quality and content, inorganic carbon, cation exchange capacity and pH conditions (Covelo et al, 2007;Flogeac et al, 2007;James and Bartlett, 1983;Palmer and Puls, 1994;Stewart et al, 2003).…”

Thermodynamics of copper desorption from soils as affected by citrate and succinate

“…The low Cu desorption associated with the clay soil suggests that most Cu ions are specifically chemically sorbed by both organic matter and layer silicate clays. The higher soil CEC generally coexisted with higher content of clay and organic matter and showed strong ability on sequestration of metals and vise versa (Stewart et al 2003).…”