Abstract
To elucidate the various characteristics of the radioactivity and negative air ion originated from an artificial thoron hot spring, we simulated a hot spring condition using a monazite powder and measured the radioactivities and negative air ions in the condition. In the result, the radioactivity of the thorium series nuclide (208Tl) in monazite was 5.3 times of that of the uranium series nuclide (214Bi). For the pH (3.5-12.5) dependence of the leaching nuclides from monazite in water, the thorium series nuclides (228Ac, 212Pb) were well leached on the strong acid side. On the other hand, the uranium series nuclides (214Bi, 214Pb) leached in water were not detected because the specific activities of the uranium series nuclides are lower relative to those of the thorium series nuclide. Moreover, there were many negative air ions originated from monazite in the place within 10 cm away from the monazite surface. This suggests that most negative ions exist within the range of the radiated &alpha rays. Negative air ions increased with increasing atmospheric relative humidity (35-60%). This suggests that negative air ions stably existed in the hydration type such as O2- (H2O)n. Furthermore, for the hydrous rate dependence of the negative air ions originated from monazite, the negative air ions without supernatant fluid were larger than those with supernatant fluid, because &alpha rays ionized water on the surface of monazite.
