Extractability of radiocesium from processed green tea leaves with hot water: the first emergent tea leaves harvested after the TEPCO’s Fukushima Daiichi Nuclear Power Plant accident

Abstract

In some tea tree planting areas within 300 km from the TEPCO’s Fukushima Daiichi Nuclear Power Plant (FNPP), it was found that newly emerged tea plant leaves for green tea contained two radiocesium species (cesium-134 and cesium-137). In this study, using processed green tea leaves for drinking, extraction ratios of radiocesium under several brew conditions were observed. When 90 °C water was used, 50–70% of radiocesium was extracted into the water, while 54–60% of radiocesium was extracted with 60 °C water. A part of radiocesium would be removed from leaves if the leaves were washed with 20 and 60 °C water before brewing, and the efficiencies were 11 and 32%, respectively. Newly emerged camellia leaves were used to simulate the radiocesium removal ratio from raw tea leaves by washing and boiling; radioactivity concentration was decreased to 60% of the original concentration with washing and 10 min boiling. From these results, it was found that almost half of the radiocesium would not be removed from raw or processed tea leaves. The values obtained in the present study could be used for internal radiation dose estimation from tea leaves.