Simple soil mass balance approach to interpret the distribution of global terrestrial gamma ray dose rates in relation to geology

A recent literature survey on natural gamma rays has yielded data on the dose rate levels above soils and rocks in the world, classified by their associated bedrock types. For comparison, the data in the Japanese Islands were also collected. The compiled results indicated a strong linear correlation between the soil and the rock dose rates. A soil–mass balance model was used to obtain the quantitative estimate of soil production and inflow rates, respectively, relative to the outflow rate. It was found from the analysis that the degree of mixing of soils, measured by the ratio between the inflow and the production rates, was fairly small in Japan compared to the world average.