Estimation of infiltration and surface run-off characteristics of radionuclides from gamma dose rate change after rain

Abstract

A method to estimate the infiltration and surface run-off characteristics of radionuclides on three types of ground surface from gamma dose rate change due to rain has been developed. We proposed the estimation methods based on the differences in the dose rate increases between monitoring stations caused by different attenuation of gamma ray due to infiltration and by the different run-off characteristics. The gamma dose rate data used for the estimation were measured at near-by monitoring stations in which the ground type around the detector differed from each other. Rain events were selected by the criteria in which 214 Pb and 214 Bi deposition amounts are considered to be uniform with in the area in which objective monitoring stations are deployed. We also calculated the surface concentration considering both infiltration and surface run-off processes. As a result, it was shown that the calculated surface concentration was about 40% larger than that considering neither processes of the infiltration and surface run-off.