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#weekendusers Following the pathway of minerals in trees


The intake of radiocesium by trees after the Fukushima disaster inspired a Japanese scientist to study in detail the mineral pathway in trees. Together with a team from Finland he was on ID21 last weekend to observe this uptake in real-life conditions.

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The Fukushima nuclear disaster in Japan, caused by the 2011 tsunami, contaminated the area surrounding the nuclear power plant. The absorption of radiocesium from the Fukushima plant into nature inspired Katsushi Kuroda, scientist from the Forestry and Forest Products Research Institute in Japan, and currently a visiting scientist at Natural Resources Institute Finland, to study the uptake of these radio elements by trees. He focused on the Japanese cedar tree, a very common species in Japan. The mineral he used in his experiments was stable isotope cesium, an element with chemical properties similar to potassium which is an essential mineral element for plants.

Kuroda had already used different techniques to study the uptake of cesium. His first challenge was to study the samples in natural conditions. In general, to analyse chemicals in trees, researchers subject the samples to dry conditions, which may alter the chemical distribution of the elements. Kuroda prepared the samples differently: he injected cesium into trunks of standing Japanese cedar trees. In living trees, water is always present, and many chemicals are water soluble. Since they easily change from their natural condition during sample collection, he freeze-fixed the tree trunk with liquid nitrogen for 30 minutes and then cut it down. The samples were kept frozen until the end of the experiments.

cedar1.jpg cedar.jpg 2017-01-27_ID21_USER-TEAM-4web.jpg (TEAM OF USERS ON ID21)

The experiment began by freezing a Japanese cedar tree to keep its natural conditions. Credits: K.Kuroada

Katsushi Kuroada and Heikki Suhonen on ID21. Credits: C.Argoud.


A while back, Kuroda met Tuula Jyske, from Natural Resources Institute Finland, at the time a post-doctoral researcher specialised in phloem properties, in his laboratory in Tsukuba. Jyske had studied bark structures at the ESRF in the past, using tomography. They both started investigating what would be the best technique for this project. Together with Heikki Suhonen, from Helsinki University, and Jussi-Petteri Suuronen, from ESRF, they spent last weekend on ID21, where they hoped to track the pathway of cesium between the bark and the wood of the tree. They used Micro-X-ray fluorescence (μ-XRF) for the element mapping, and Micro-X-ray absorption near edge structures spectroscopy (μ-XANES), in order to detect whether cesium is movable or binding to the cell structure.

“The data will give us a broader view of how mineral transportation happens in trees”, Jyske explains. Kuroda continues: “It will also reveal how the trees were contaminated by radiocesium after the Fukushima nuclear power plant accident in Japan, and will help predict the future distribution of radiocesium in trees”.

2017-01-27_ID21_USER-TEAM-1web.jpg (TEAM OF USERS ON ID21)

Text by Montserrat Capellas Espuny

Top image: Image taken by X-ray fluorescence on ID21 of minerals showing the clear cell structure of the tree.