Reprint of “Vertical migration of radio-caesium derived from the Fukushima Dai-ichi Nuclear Power Plant accident in undisturbed soils of grassland and forest”

Meta-analysis of radiocesium contamination data in Japanese cedar and cypress forests over the period 2011–2017

“…Our estimates are closer to the value reported in the IAEA technical report (2010) for sandy soils (GM=530 L kg-1 d.w) than organic soils (GM=270 L kg-1 d.w). Our estimate is about twice that reported by Mishra et al (2018) for the 0-20 cm mineral soil of a few Fukushima coniferous forests, i.e. typically less than 250 L kg-1 d.w.…”

“…This gives a mean residence time between 6.5 to 8.5 years, which is definitely longer than in the above layer due to the immobilization/fixation of a large proportion of incoming radiocesium through a variety of physico-chemical mechanisms. Such a residence times correspond to migration velocities between 0.59 and 0.77 cm y-1, in the lower range of those measured by Mishra et al (2018) in Fukushima coniferous forest soils based on a few measurements of activity profiles in 2012 and 2013. A simplified approach to estimate the residence time r in a mineral horizon of depth h is to express it in terms of an apparent distribution coefficient, KD (l/kg), based on the following relationship: r » Ln(2)/I*p *h*KD where I (L m-2 y-1) represents the effective annual water percolation 36/57 flux across the layer.…”

“…Manaka et al (2019) demonstrated that the proportion of exchangeable radiocesium in the top 5 cm mineral layer at one of their coniferous sites (KAJI sites) was about half that measured in the organic layer. The higher availability of radiocesium in organic soil was ascribed to a lower amount of silt-and clay-sized particles or the inhibition by well-decomposed organic matter of radiocesium adsorption on clay minerals (Koarashi et al, 2012b;Mishra 2018). Going back to Fig.…”

“…organic, 0-5 and 5-10 cm) to the underlying one, the value of which will be assumed constant over time. These migration rates can be expressed in terms of residence half-life tj=Ln(2)/Àj (d), which in turn can be converted into an mean migration velocity, v=hj/Tj (m d-1) where hj (m) is the layer's thickness, when comparing soil horizons of different thicknesses (Frissel and Pennders, 1983;Boone et al, 1985;Mishra et al, 2018). The parameters j quantify the contribution of each layer to the total root uptake, with the constraint that E^up=1.…”

Caesium desorption from layer silicate minerals using quaternary ammonium salts

“…A large amount of Cs was adsorbed onto lamellar minerals in the soil after the accident at Fukushima Daiichi Nuclear Power Plant in 2011 (Murota et al, 2016;Onodera et al, 2017;Mishra et al, 2018). Caesium elution from contaminated materials collected may cause secondary contamination.…”