Uranium complexes geochemistry

Surface analytical techniques. A variety of spectroscopic methods have been used to characterize the nature of adsorbed species at the solid-water interface in natural and experimental systems (Brown et al, 1999). Surface spectroscopy techniques such as extended X-ray absorption fine structure spectroscopy (EXAFS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) have been used to characterize complexes of fission products, thorium, uranium, plutonium, and uranium sorbed onto silicates, goethite, clays, and microbes (Chisholm-Brause et al, 1992, 1994 Dent et al, 1992 Combes et al, 1992 Bargar et al, 2000 Brown and Sturchio, 2002). A recent overview of the theory and applications of synchrotron radiation to the analysis of the surfaces of soils, amorphous materials, rocks, and organic matter in low-temperature geochemistry and environmental science can be found in Fenter et al (2002). 

Davis J. A., Payne T. E., and Waite T. D. (2002) Simulation of the pH and pC02 dependence of Uranium(VI) adsorption by a weathered schist with surface complexation models. In Geochemistry of Soil Radionuclides (eds. P. Zhang and P. Brady). Soil Science Society of America, pp. 61-86. 

The extraction of dates from the uranium and thorium isotope ratios in speleothems depends on a quirk in the geochemistry of these two elements. Uranium is easily oxidized to the state where it usually appears as the U02 ion. The uranyl ion in addition to its intrinsic solubility also forms soluble carbonate complexes that further mobilize the element in karstic ground waters (Langmuir, 1978, 1997). Thorium is firmly locked into the insoluble Th" state and is immobile in ground water (Langmuir... 

Uranium geochemistry is controlled by the ambient redox environment, pH and concentrations of inorganic and organic complexing ligands [17, 18]. Constraints on Eh, pH and carbonate concentrations are interpreted below based on hydrochemical and mineralogical data obtained in field studies of the Tono Uranium Deposit and nearby vicinity. Iwatsuki et al. [19] and... 

Davis, J.A., T.E. Payne, and T.D. Waite. 2002. Simulating the pH and pCO-i dependence of uranium(IV) adsorption by a weathered schist with surface complexation models, p. 61-86. In Geochemistry of soil radionuclides. SSSA Spec. Publ. 59. SSSA, Madison, WI. 

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