Evaluation of Natural Radioactivity inSubsurface Air, Water and Soil in Western Japan

摘要

Surveys of radon concentrations in western Japan were carried out to estimate thecontents not only of waters in the environment but also in soil gas. The maximum concentrationmeasured for drinking water as public supply exceeded the 1991 United States EnvironmentalProtection Agency-recommended limit for drinking water (11 Bq L~(-1)) but did not exceed that ofseveral European countries (100 Bq L~(-1)). Overall, the concentrations of radon in subsurface waterranged from 1 to 100 Bq L~(-1)and those in surface water were below 1 Bq L~(-1) in a residential area.Fifty nine samples in soil gas at 4 Prefectures of the Kinki district were analyzed together with 19samples of interest due to karst and uranium mining sites from another two Prefectures to compare222with the above samples. The cumulative frequency of the ~(222)Rn-concentrations both inenvironmental water and soil gas showed a log-normal distribution. Surveys of naturalradioactivity in soils were also carried out with a Ge(Li) detector to determine the concentrations.