Characterization of the frayed edge site of micaceous minerals in soil clays influenced by different pedogenetic conditions in Japan and northern Thailand

Abstract

Radiocesium interception potential (RIP), a quantitative index of a frayed edge site of micaceous minerals, was investigated on test clay minerals (illite, kaolinite, montmorillonite and vermiculite) and soil clays formed under different pedogenetic conditions in the Kinki district of Japan and in northern Thailand to elucidate the effect of pedogenetic weathering on the amount of frayed edge site of micaceous minerals. ) compared with illitic minerals (4.3 mol kg -1 in silt size; 11.8 mol kg -1 in clay size) suggested that the frayed edge site increased as the expanded layer formed in the micaceous minerals. In northern Thailand soil clays, the absence of a vermiculitic expanded layer was indicated. Periodic wet-dry conditions may restrict K depletion from micaceous minerals in the region. It is concluded that micaceous minerals were weathered without layer expansion and, therefore, the amount of the frayed edge site was regulated by the content of micaceous minerals in northern Thailand. In Japanese soil clays, large RIP values were found in the EB and Bs horizons of a Podzodic profile (SW1), which had large vermiculitic expanded layers like the test vermiculite. However, the RIP values drastically decreased from the Bs to E horizon, maintaining a high vermiculitic layer charge. Thus, intensive weathering in highly acidic soils in Japan might reduce the frayed edge site.

Potassium fertilizer and other materials as countermeasures to reduce radiocesium levels in rice: Results of urgent experiments in 2011 responding to the Fukushima Daiichi Nuclear Power Plant accident

“…The XRD chart for the field B soil clearly shows the presence of expansible 2:1 clay minerals. Fixation of radiocesium by expansible 2:1 clay minerals (Nakao et al 2008) appears to be related to low TF values in field B. The RIP was not measured in the present experiment, so we cannot confirm this hypothesis without additional research.…”

“…The contamination of paddy fields will last for a long time, because the half-life of 137 Cs is about 30 years and the mobility of radiocesium in field soils is very low (Nakao et al 2008). Moreover, paddy rice may uptake more radiocesium than other upland crops (Tensho et al 1959).…”

Mechanism of Strong Affinity of Clay Minerals to Radioactive Cesium: First-Principles Calculation Study for Adsorption of Cesium at Frayed Edge Sites in Muscovite

“…The RIP value is known to be about 0.006 mol/kg in kaolinite, one of the 1:1 phyllosilicates, while that in mica reaches 11.8 mol/kg, indicating the strong and selective affinities of Cs to FESs. 17) Indeed, scanning electron microscopy and X-ray microprobe measurements roughly confirmed that radioactive Cs is fixed only around the edge of micas. These results strongly support the selective affinity for Cs of FESs.…”

Adsorption behavior of radioactive cesium by non-mica minerals

“…The capacity of the "frayed edge" sites of illite and sericite is sufficient for Cs at 10 −9 mole L −1 , reflecting our present sequential desorption behavior observation that most of the adsorbed Cs was residual after the desorption treatment. On the other hand, a pure mica structure reversibly adsorbs Cs [27,28]. In the present experiments, for Cs at 10 −4 mole L −1 , most of the Cs adsorbed by illite and sericite was desorbed by the three reagent solutions.…”

“…The "frayed edge" site of kaolinite was estimated by radiocesium interception potential (RIP) to approx. 1 × 10 −8 mol g −1 [30], being lower by 1000 than that of illite [31]. Thus, approx.…”