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Interview with Tomoko Nakanishi
Click here to read the Japanese version of this interview.
Tomoko Nakanishi is Professor at the Graduate School of Agricultural and Life Sciences, The University of Tokyo, and a leading expert in radio-plant physiology.
Immediately after the Fukushima Nuclear Accident in 2011, the academic staff members at the The University of Tokyo's Graduate School of Agricultural and Life Sciences organized research groups to determine the impacts of the fallout on the agricultural fields in Fukushima Prefecture. This research project still continues and supports Fukushima’s remediation and recovery.
Professor Nakanishi, a leading member of the research project, speaks about their five years of on-site research in Fukushima, important scientific findings, and about open access books based on the outcomes of the project, Agricultural Implications of the Fukushima Nuclear Accident (2013) and Agricultural Implications of the Fukushima Nuclear Accident: The First Three Years (2016), which she co-edited.
– Will you tell us about the research project?
Based on the fact that 80% of the area polluted by the Fukushima Nuclear Accident was agricultural land including forests, the academic staff from the Faculty of Agriculture established an investigation team consisting of around 50 volunteer members immediately after the Accident. The studies on soil, water, crops, animals and the environment itself required interdisciplinary cooperation. For instance, the team has sampled soil for the depth distribution measurement of radioactive cesium (hereinafter “cesium”) and studied the mechanisms on how rice or soybean incorporates cesium or how it can be prevented. Agriculture studies the nature, which works in a great time scale and has a deeper mechanism. Another important is a connection with people as we would not be able to investigate anything without a relationship of trust with local farmers. These studies reminded us of the importance of on-site investigation.
– How does radio-plant physiology, the area of your expertise, relate to the disaster?
Radio-plant physiology is an area of study that covers the biological activities of plants by means of radioisotope and radiations. This technology is an outstanding “tool” capable of quantitative measurement of an ultratrace amount of atoms. For instance, we utilized the tool and developed a means to create an image of how water and nutrients move in living plants. We have aimed to contribute to improving agricultural techniques through a deeper understanding of plants. I was keen on keeping myself updated on the Chernobyl accident at its occurrence in 1986, when I never dreamed of engaging in studies on disasters including pollution accidents. Upon the occurrence of the accident at Fukushima, I successfully investigated the actual condition of radioactive contamination on the basis of my past research and studies.
– What are the most important findings gained from your 5-year studies since the Earthquake?
There are particularly two major findings on the behavior of cesium. The first finding was that a tree absorbs cesium from the bark of its trunk. This was surprising in the sense we usually think it absorbs cesium from its root just like it absorbs water. Another finding was the fact that only a specific type of mineral (weathered biotite) absorbs cesium while cesium is firmly immobilized. It had been unknown what mineral in soil would absorb cesium.
– What were the misunderstandings about radioactive contamination?
We had no idea of what to do as something no one had ever experienced was going on. It was originally thought that plants continuously absorbed cesium from soil and cows that took such polluted grass were also polluted, many of which were therefore euthanized. It was however revealed that an extremely low proportion of cesium firmly immobilized in soil flowed out to rivers or groundwater, or was absorbed into crops unless it was immediately after its deposition. Cesium was detected from the milk of those cows which took polluted feed, but such milk was no longer polluted in two weeks after the same cows started taking unpolluted feed. Looking back, there might have been no need to euthanize them.
– What kind of response did you receive after the publication of the first book on the project outcomes, Agricultural Implications of the Fukushima Nuclear Accident, in 2013?
I was interviewed by a number of media from the UK, US, Netherlands and many other countries immediately after the publication of the book. It was the first major publication of the research outcomes on radioactive contamination resulting from the Earthquake disaster. We decided to make the publication open-access to widely transmit information overseas, and the electronic version was downloaded many times.
– Please tell us about your second open access book, Agricultural Implications of the Fukushima Nuclear Accident: The First Three Years, which has just been published.
Our second publication summarizes the research outcomes on the more detailed mechanisms of polluting plants or soil and on the decontamination method based on the data obtained for three years after the Earthquake disaster. For example, the research presented that rice well absorbed cesium if hydroponically cultivated but hardly absorbed it if cultivated in paddies or soil (figure on the right: cesium uptake by rice seedlings planted in water, left, and on soil, right).
An analysis of soil samples taken in Japan before the Earthquake revealed how radioactive fallout the US and USSR nuclear tests was distributed on the Earth in the 1960s behaved in soil. Cesium in soil sinks an average a millimeter deeper under the ground annually, which is surprisingly slow. This is an important insight which serves as the basis of predicting the future behavior of cesium emitted as a result of the Earthquake disaster.
– It is also important to provide information to the general public, isn’t it?
The major incident like the Fukushima accident exposes the general public to diverse information which makes people tired of it. The feeling of anxiety also prevents them from proper understanding. It is therefore extremely difficult to let people understand a finding even if it is new, data-based and important. They however felt relieved when I showed them the images created based on the data on cows, plants and other objects familiar to us. The implication of difficult data is made much simpler and easier to understand by visualizing it with images.
– What role should scientists play when a disaster or nuclear accident occurs?
We failed to make full use of the detailed research outcomes on soil contamination at Chernobyl as they were written in Ukrainian. Although nuclear accidents should never happen again, it is extremely important to keep an English record of the precise data measured in preparation for such accidents. Our studies this time focus particularly on the behavior of cesium in rice and paddies, which would be very useful in the Asian monsoon region where rice cultivation accounts for the major proportion of agriculture. In the natural world with slow time flow, a three-year period allows us to only investigate three cycles of the biological activities of plants if a year makes a cycle. I would like to continue this research for 10 years at a minimum, which means at least another 5 years from now on.
Agricultural Implications of the Fukushima Nuclear Accident
Editors: Nakanishi, Tomoko M., Tanoi, Keitaro
Agricultural Implications of the Fukushima Nuclear Accident: The First Three Years
Editors: Nakanishi, Tomoko M., Tanoi, Keitaro