Chapter 17 Dissolution chemistry of inorganic selenium in alkaline mine soils

摘要: Abstract Selenium (Se) is a natural geological constituent in many mining areas of the western United States. While Se an essential micronutrient for humans and animals, its low toxicity threshold poses health concerns. Oxidative exposure excavated mine soils leads to increased concentrations selenite (SeIVO32−) selenate (SeVIO42−) species, which can potentially enter food chain. To ascertain geochemical processes contributing bioavailability, we examined dissolution, speciation, fractionation, adsorption, solid phases coal uranium from Wyoming. The were alkaline nature, majority (86%) labile remained exchange phase. Despite 49% total levels identified siliceous minerals, exchangeable exceeded critical limit >60% samples. SeVI SeIV dominant species aqueous fractions, respectively. was major that dissolved under condition. primarily related ligand or complexation processes. Mine adsorbed up 99% 95% SeVI, relative sorption on average six-fold higher SeIV. Occurrence oxides oxyhydroxides Ca, Mn, Fe soil resulted greater retention, mostly augmented presence Fe-minerals. solutions undersaturated with respect phases, thereby suggesting precipitation would less likely prevail. CaSeO3·2H2O CaSeO4 only solids vicinity saturation equilibrium line. Fe2O3, CuFe2O4, ZnFe2O4, CuFeO2, FeOOH, Fe3O4, CaFe2O4, MgFe2O4, Al(OH)3, Al2O3, CuO, Cu4(SO4)(OH)6 primary saturated mineral could bind Se. These results are germane chemistry earth materials pedochemical weathering.