環境

Based on the results of the Study on Radionuclides in the Water of Tama River Using Linen Cloth conducted between October 2015 and September 2016, we carried out this study to delve more deeply into the current situation by expanding the scope of the survey and using a method that enabled us to directly capture specimens of radionuclides in sludge and waste water discharged from specific facilities and structures. We aimed to develop a commercial method of measuring those radionuclides, in addition to conducting verification tests and unraveling the mechanism of radioactive contamination of rivers occurring on an extensive scale throughout eastern Japan, with the objective of providing local governments with suggestions for preventing such contamination, as well as seeking to prevent unnecessary exposure by warning river users of high-risk locations. Moreover, we sought to confirm which locations were safe in order to provide children with an environment in which they can encounter nature safely and with peace of mind. As a result, we ascertained that radiocesium was still present in streams throughout the Tama River basin as of 2017 and that radiocesium concentrations in streams throughout the Tama River basin are changing over time, with areas with a high concentration of radiocesium moving further downstream. We found that there is an area with a high concentration of radiocesium even upstream of the wastewater treatment center’s discharge outlet thought to be the source of contamination, and that there are extreme variations in radiocesium concentrations between winter and summer.

Noriyuki Itoh