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

Abstract

The Department of Defense (DoD) is faced with the daunting task of possible remediation of numerous soil-Cr(VI) contaminated sites throughout the continental U.S. The primary risk driver at these sites is hand-to-mouth ingestion of contaminated soil by children. In the following study we investigate the impact of soil geochemical and physical properties on the sorption and bioaccessibility of Cr(VI) in a vast array of soils relevant to neighboring DoD sites. For the 35 soils used in this study, A-horizon soils typically sorbed significantly more Cr(VI) relative to B-horizon soils. Multiple linear regression analysis suggested that Cr(VI) sorption increased with increasing soil total organic C (TOC) and decreasing soil pH. The bioaccessibility of total Cr (CrT) and Cr(VI) on the soils decreased with increasing soil TOC content. As the soil TOC content approached 0.4%, the bioaccessibility of soil bound Cr systematically decreased from approximately 65 to 10%. As the soil TOC content increased from 0.4 to 4%, the bioaccessibility of Cr(VI) and CrT remained relatively constant at approximately 4% and 10%, respectively. X-ray absorption near edge structure (XANES) spectroscopy suggested that Cr(VI) reduction to Cr(III) was prevalent and that the redox transformation of Cr(VI) increased with increasing soil TOC. XANES confirmed that nearly all bioaccessible soil Cr was the Cr(VI) moiety. Multiple linear regression analysis suggested that the bioaccessibility of Cr(VI) and its reduced counterpart Cr(III), decreased with increasing soil TOC and increasing soil pH. This is consistent with the observation that the reduction reaction and formation of Cr(III) increased with increasing soil TOC and that Cr(III) was significantly less bioaccessible relative to Cr(VI). The model was found to adequately describe CrT bioaccessibility in soils from DoD facilities where Cr(VI) contaminated sites were present. The results of this study illustrate the importance of soil properties on Cr(VI) sorption and bioassessability and help define what soil types have the greatest risk associated with Cr(VI) exposure.

Vanadium Speciation by XANES Spectroscopy: A Three‐Dimensional Approach

“…Despite the recent developments in theoretical XANES calculations for V and other transitionmetal species [3a, 11] determination of average coordination environments of metal ions in complex biological or environmental matrices still relies on empirical techniques, such as principal component analyses or multiple linear regression fitting. [1,12] Our group has previously applied empirical analyses of XANES spectra, based on the use of libraries of model compounds, to a variety of problems related to the reactivity of toxic and medicinal metal ions in biological media. [1b, 13] In this work, we developed a library of V V , V IV and V III complexes with biological or biomimetic ligands (1-18 in Figure 1), primarily for biotransformation studies of V-based anti-diabetic drugs.…”

Mechanism and modeling of hexavalent chromium interaction with a typical black soil: the importance of the relationship between adsorption and reduction

“…4,5 As known, Cr(VI) is extremely toxic and carcinogenic to plants and human beings, 6,7 which is considered as one of the four top priority soil heavy metal contaminants of concern by United State Department of Defense. [8][9][10] The soil layer has been found to have signicant retention effect on the migration of Cr(VI) towards groundwater, and many investigations have focused on the topic of Cr(VI) adsorption by soils. 11,12 It has been extensively reported that Cr(VI) anions (Cr 2 O 7…”

“…2À , HCrO 4 À and CrO 4 2À ) tend to be bound to positively charged soil particles by forming inner-sphere (specic adsorption) or outer-sphere (non-specic adsorption) complexes, 8 and the adsorption of Cr(VI) by soil is mainly inuenced by pH condition, electrolyte species, inorganic minerals (e.g. iron oxides, aluminum oxides, manganese oxides, and clay) and organic matters (e.g.…”

“…The adsorption determines the macroscopic retention effect of Cr(VI) migration, while the reduction determines the toxicity (environmental risk) and stability (leaching potential) of Cr. 8 These two processes interplay with each other, neither of which should be ignored. However, the adsorption and reduction of Cr(VI) were always investigated separately in previous studies resulting from the unclear relationship between them.…”

Testing single extraction methods and in vitro tests to assess the geochemical reactivity and human bioaccessibility of silver in urban soils amended with silver nanoparticles

“…Hence, it was considered of merit to use the knowledge on existing extraction tests and in vitro bioaccessibility studies for several metals (Wragg and Cave, 2002;Jardine et al, 2013;Mukhtar and Limbeck, 2013;Pêlfrene et al, 2013;Rodrigues et al, 2013) to study Ag geochemistry and to test both the geochemical reactivity and bioaccessibility of AgNPs in soils.…”