Volcanic ash as a factor in the generation of radioecological conditions in Kamchatka part II. The radiogeochemical properties of environmental components

Abstract

An area where fresh volcanic ash has fallen was found to have concentrations of Th and U that exceed the background values by factors of 270 and 32, respectively, for natural waters and by factors of 35 and 6 for plants. The soils and bottom deposits were not enriched in Th and U after a single ashfall; however the Th/U ratio decreased in these natural media relative to the background values, indicating a genetic affinity with young ashes where the concentration of highly mobile (relative to thorium) uranium is higher compared with older ashes. For areas far from active ashfalls, where the soils were formed on acid ash, we found higher background concentrations of Th and U in soils, surface waters, and bottom deposits, as well as higher gamma-ray background values above the Earth’s surface relative to the areas where the soils were formed on basic and intermediate ashes. This research resulted in the identification of two radioecological provinces in Kamchatka, viz., a Northern and a Southern province.