Long-lived radon daughters, 210Pb and 210Po, in volcanic products and hot and mineral spring waters

Lead-210 and Po-210 in volcanic gases and sulfur sublimates have been measured for several volcanoes in Hokkaido and kyushu districts. Furthermore, more than 40 water samples in mineral and hot springs were subjected to the analysis of Pb-210 and Po-210, along with other natural radionuclides U-238(U-234), Ra-226(Ra-228) and Rn-222. The sources of (210)pb and Po-210 with regards to volcanic origin and behaviors of supply and removal of these nuclide were discussed based on the analytical date. In volcanic samples, excess of Po-210 was observed and the results indicated that the concentrations of Pb-210 and Po-210 and the activity ratios of Po-210/Pb-210 in volcanic gases and also in sulfur sublimates depended highly on the temperature of fumarolic gases. Wide variations in Po-210 in (210)pb and Po-210 concentrations have been observed in sulfur sublimates. On the other hand, even for hot springs in volcanic area the concentrations of Po-210 in the water samples were not so high. It was considered that Po-210 from volcanic gases was easily removed from water to the surface of rocks and soils, as suggested by the data of sulfur sublimates, The concentrations of Pb-210 and also Po-210 were, however, found to be higher in the springs of high Rn-222 concentrations, indicating that (210)pb (and Po-210) in springs water may be useful as a guide to elucidate the origin, ages of water sources and of the history of Rn-222 in the springs.