Nuclear Magnetic Resonance Study of Cs Adsorption onto Clay Minerals

Abstract

The release of radioactive cesium into the environment in the aftermath of disasters such as the Fukushima Daiichi disaster poses a great health risk, particularly since cesium easily spreads in nature. In this context, we perform solidstate nuclear magnetic resonance (NMR) experiments to study Cs C ions adsorbed by clay minerals to analyze their local structure. The NMR spectra show two kinds of peaks corresponding to the clays (illite and kaolinite) after immersion in CsCl aqueous solution; the peak at 30 ppm is assigned to Cs C on the clay surface while that at 100 ppm is assigned to Cs C in the silicate sheet in the clay crystal. This result is consistent with the fact that Cs C with smaller coordination number yields a small field shift in the NMR spectra. Moreover, after immersion in KCl aqueous solution, these peaks disappear in the NMR spectra, thereby indicating that our assignment is reasonable. This is because Cs C on the clay surface and in the silicate sheet is easily subject to ion exchange by K C . We believe that our findings will contribute to a better understanding of the pathway through which Cs transfers from the soil to plants and also to the recovery of the agriculture in Fukushima.

Spatiotemporal distribution and fluctuation of radiocesium in Tokyo Bay in the five years following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident

“…Therefore, radiocesium precipitated from atmosphere on ground surfaces is absorbed and held by clay minerals in the soil. Recently, it has been confirmed directly that radiocesium released from the FDNPP is adsorbed by the clay mineral using a new technic such as EXAFS and NMR [ 48 – 50 ]. Moreover, fine particles with a particle size of 10 μm or less containing radiocesium at high activity are found in various places of eastern Japan [ 51 – 55 ], but we believe that washout due to rainfall plays an important role in precipitation on the ground even if radiocesium is scattered in the atmosphere as gaseous or fine particles.…”