Microparticles containing substantial amounts of radiocesium collected from the ground in Fukushima were investigated mainly by transmission electron microscopy (TEM) and X-ray microanalysis with scanning TEM (STEM). Particles of around 2 μm in diameter are basically silicate glass containing Fe and Zn as transition metals, Cs, Rb and K as alkali ions, and Sn as substantial elements. These elements are homogeneously distributed in the glass except Cs which has a concentration gradient, increasing from center to surface. Nano-sized crystallites such as copper- zinc- and molybdenum sulfide, and silver telluride were found inside the microparticles, which probably resulted from the segregation of the silicate and sulfide (telluride) during molten-stage. An alkali-depleted layer of ca. 0.2 μm thick exists at the outer side of the particle collected from cedar leaves 8 months after the nuclear accident, suggesting gradual leaching of radiocesium from the microparticles in the natural environment.
Read more here
(a) Element maps of NWC-1 acquired by STEM-EDS with a STEM Dark-field (DF) image at the same area, and (top) TEM Bright-field image in which the rectangle indicates the area analyzed by STEM-EDS. The thin area around the top of the particle which was not observed in Fig. 1a was formed by a further thinning process by FIB. (b) Element maps and images of CB-8 with the same framing as in (a).