How can we predict soil-to-plant transfer risk of radiocesium? Dr Atsushi Nakao

Even nine years have already passed after the accident at the Fukushima Dai-ichi Nuclear Power Plant, radicesium contamination is still a public concern in Japan and other neighboring countries. Long before the accident, it is scientifically known that soil-to-plant transfer of radiocesium is generally very low due to strong retention by micaceous clay minerals in soil. Partially expanded micaceous clay minerals have a specific interlayer site with 1.1~1.2 nm d-spacing, named as a fayed edge site (FES). This site has much high ionic adsorption selectivity for Cs+ than other cations, thereby isolating radiocesium from nutrient cycles. In case of investigations in Europe after the Chernobyl accident, the FES content was found to be proportional to clay content. Relatively homogeneous clay mineralogy may be behind this simple relationship. However, in case of Japan, the FES content was highly variable and not related to clay content, which makes prediction of soil-to-plant transfer risk rather difficult. In this seminar, I will introduce the fundamental mineralogy related to the formation of FES in micaceous minerals, explain why the FES content is highly variable depending on soils in Japan, and then suggest the promising soil management strategy to prepare against radiocesium contamination.

Atsushi Nakao received his ph.D. in Agriculture from the Kyoto University in 2008. After completion of his degree, he was appointed as a Post-doc in the soil science laboratory of Kyoto University (2008-2009) and in the Institute for Environmental Sciences (2009-2011). In November 2011, he moved to Kyoto Prefectural University and was appointed as a faculty member of the Department of Life and Environmental Sciences, Kyoto University. His interests are focused on soil mineral functions to control elemental dynamics in the terrestrial ecosystems. In particular his laboratory is currently working on understanding the role of micaceous minerals controlling sol-to-plant transfer of radiocesium. His research and impact have been recognized through various awards including: The Incentive Award from JSSPN (2015); Japan Prize in Agricultural Sciences, Achievement Award for Young Scientists (2016).