| Aqueous radioactive metals leaking from waste storage tanks at Department of Energy waste storage facilities have contaminated the soils. The interactions with natural soil particles govern the mobility of radionuclides (such as 137Cs and 90Sr) in the saturated and unsaturated zones of mineral systems at contaminated sites (e.g. Hanford Site, Savannah River Site). High surface area aluminosilicate clay minerals, a soil component at these sites, are recognized as important radionuclide sequestrants. The extreme characteristics of the contaminant medium (high pH, high Al content, and high ionic strength) promote mineral dissolution, which affects the environmental fate and availability of harmful nuclei in the subsurface environment. Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful analytical tool capable of studying amorphous and crystalline aluminosilicate mineral phases such as soils. This work utilizes the following SSNMR techniques in an attempt to accomplish the major goal, which is to gain a better understanding of fundamental processes taking place in the vadose and saturated soil environments using specimen clay samples in environments that approximate those present at the Hanford site in Richland, WA. Low field (400 MHz for 1H) 27Al and 29Si MAS NMR are used to evaluate changes in the coordination environment of aluminum and silicon, which would indicate the formation of secondary mineral phases. Additionally, high-field (750 MHz for 1H) 27Al MAS NMR is used in conjunction with 400 MHz data to calculate the quadrupolar interaction product for all aluminum environments along with the isotropic chemical shifts of each observed resonance. Finally, more advanced double-resonance techniques such as 1H/29Si Cross-Polarization with Magic Angle Spinning (CPMAS), 29Si/133Cs Transfer of Populations at Double Resonance (TRAPDOR) and 29Si/133Cs Rotational Echo Double Resonance (REDOR) NMR are used in an attempt to identify spectroscopically the specific cesium-containing phases. |
