Journal of Radioanalytical and Nuclear Chemistry, Volume 295, Issue 3, 2013 (emphasis added): [...] radionuclides were emitted from the FDNPP as airborne ‘hot’ particles [...] Subsequent interaction of the ‘hot’ particles with water (e.g. rainfall) dissolved and strongly fixed the radiocesium on rock and soil particles, thus changing the radiocesium into insoluble forms. [...] Consequently, ‘hot spots’ were studded on the rock surface rather than being uniformly distributed. [...] Leaching experiments demonstrated that radiocesium in rock, soil and river suspended sediment was fairly insoluble, showing that the adsorption [binding of particles to a surface] reaction is irreversible. The micro-scale heterogeneous distribution of radiocesium [...] was due to the presence of ‘hot’ particles in aerosols. [...] ‘hot’ particles in the aerosols [experienced] irreversible adsorption onto the soil particle complex [...]
Agricultural Implications of the Fukushima Nuclear Accident – Radiocesium Absorption by Rice in Paddy Field Ecosystems (pdf), 2013: Unexpectedly, we found that the fallout was relatively insoluble and only a small percentage of the radiocesium could be extracted by a boiling water treatment followed by nitrate leaching. We have very little knowledge about this fallout, including its chemical form and properties, but huge amounts of this relatively insoluble radioactive fallout are still bound to organic matters [...]
Presentation by Yasuhito Igarashi of Japan’s Meteorological Research Institute at IAEA’s expert meeting (pdf), February 2014: Mar. 14-15 sample contained insoluble materials not only in water but hot nitric acid! […] They are insoluble; even refractory to conc. nitric acid. [...] They would persist for a long time in the environment as well as in living organisms.
Scientific Reports (Nature Publishing Group) — Emission of spherical cesium-bearing particles from an early stage of the Fukushima nuclear accident, Aug. 30, 2013: We analyzed the water solubility of Cs Particle 1 by comparing the particle’s shape before and after exposure to water. The results show that there was no change in shape, suggesting that the particle was insoluble to water at least during atmospheric transportation.
American Chemical Society Publication, Analytical Chemistry — Detection of uranium and chemical state analysis of individual radioactive microparticles emitted from the Fukushima nuclear accident… (Tokyo Univ., Japan’s Meteorological Research Institute), August 1, 2014: We explored the possible sources of the 14 elements (Cr, Mn, Fe, Zn, Rb, Zr, Mo, Ag, Sn, Sb, Te, Cs, Ba, and U) found within the microparticles [...] These particle natures suggest that they could have relatively long-term impact on the environment, i.e., the release of soluble radioactive Cs into the environment as these insoluble glassy particles degrade. Similar radioactive particles have been detected in soils, plants, and mushrooms [...] it is probable that [these particles are] the same as the microparticles characterized in our study.
See also: Scientists: 'Spheres' of radioactive material from Fukushima reported for first time -- Ball-like particles composed of cesium, iron, zinc -- Solid and insoluble in water -- Impact on human health needs to be examined (PHOTOS)
Published: August 12th, 2014 at 9:44 am ET