Water Quality Analysis for Comprehensive Evaluation of Combined Exposure from Heavy Metals and Radionuclides

抄録

Ever since the accident at TEPCOʼs Fukushima Dai-ichi Nuclear Power Plant (FDNPP) has passed for 12 years, a part of residents is still concerned about radiation exposure to radionuclides from the environment. Our study employed a method that compares the effects of anthropogenic and natural radionuclides, evaluating the dose exposures to ambient radiation, inhalation of atmospheric aerosols, and ingestion of drinking water on three municipalities in the Hamadori region of Fukushima Prefecture, near the FDNPP. This presentation focuses on the analysis of water samples used as drinking water. Particularly in Kawauchi, well water is the primary source for drinking, distinguishing it from the other areas. All water sources for drinking undergo regular analysis for water quality and radionuclide concentrations by the local government, being lower the guidance level of drinking water in Japan. Drinking water samples were collected from tap water or well water used in residentsʼ homes at Kawauchi, Tomioka and Okuma from March 2022 to March 2023. In addition to ²²²Rn and ¹³⁷Cs concentrations analysis, concentrations of major ions and trace elements including Cd, As, Cr, Pb, Cs (stable) and ²³⁸ U were determined by ion-chromagraphy and ICP-MS. ²²²Rn concentrations obtained at Kawauchi, Tomioka, and Okuma ranged from 17–399 Bq L ^-1 , <55 Bq L ^-1 , and <12 Bq L ^-1 , respectively. Notably, the ²²² Rn concentrations in six out of ten houses at Kawauchi exceeded 100 Bq L^-1 as a reference level reported by the EU. Abukuma granite belt, characterized by elevated ²³⁸ U concentrations, is widely distributed as bedrock in Fukushima Prefecture including Kawauchi. High concentration of ²³⁸U were observed in water samples collected from Kawauchi and Okuma, with maximum of 0.039 Bq L ^-1 . This observation suggests that ground water played a significant role in interacting with granite bedrock and transporting ²³⁸U. This work was supported by the Research Project on the Health Effects of Radiation organized by the Ministry of the Environment, Japan.