Dr. Tsubokura's Radiation Lecture Vol.57

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

113. Cesium is absorbed differently by each plant

Plants grow by absorbing minerals and water from the soil through their roots. When radioactive cesium is present in the soil, the plant will absorb it along with nutrients, and this results in contamination.

Previous investigations have revealed that the extent of contamination differs by plant type. In detail, the rate of absorbed radioactive cesium compared to that in the soil could vary from approximately 1/1000 to 1/10,000 depending on the type of plant (called the transfer coefficient).

For example, leafy vegetables such as Japanese mustard spinach, spinach, potato, and broccoli tend to be contaminated at slightly higher levels (they absorb cesium easily) compared to cabbage, cucumber, and eggplant. In contrast, rice absorbs cesium the least.

Besides the nature of vegetables themselves, various countermeasures, such as soil decontamination and a redesigning of cultivating methods and fertilizer types, were taken to reduce the level of contamination in agricultural products. As a result, radioactive substances are no longer detected in most agricultural products today.

114. Use of potassium to protect plants from radiation contamination

The radioactive substances attached to dust and dirt in the atmosphere are measured with a device called an air sampler. It takes in a large quantity of air over several hours and passes the collected air through a filter. After this process, the level of radioactive substances (mainly cesium) remaining on the filter is measured.

It would not be correct to say that no cesium is detected, but cesium has seldom been detected in the air, even in the evacuation zones. Furthermore, cesium was only detected when the measurement time reached several hours, and the detected level of cesium was just slightly above the device’s detection limit. The detected radioactive substances were not from the nuclear power plant but were carried with soil in the wind after rainfall.

Ventilation in buildings is crucial to hygiene and humidity control. It is safe to open windows to ventilate the home, not only outside of the evacuation zones but also in the area where the evacuation order was lifted. In these areas, it is unnecessary to be concerned about your laundry being polluted with radiation after drying it outside or having adverse health risks due to external exposure.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on March 12th and 17th 2017 was reproduced for MRIC Global under the author's permission.