Radioactivity in Precipitation

Radioactivity in Precipitation 

radioactivity caused by the capture of radioactive aerosols and atmospheric gases by cloud and precipitation particles. Furthermore, the water of precipitates itself contains atoms of radioactive ³H. A distinction is made between the natural and artificial radioactivity in precipitation, depending on the origin of the radioactive aerosols and gases that are removed from the atmosphere. The highest level of radioactivity corresponds to the short-lived decay products of ²²²Rn, namely, ²¹⁸Po(RaA), ²¹⁴Pb(RaB), ²¹⁴Bi(RaC), and ²¹⁴Po(RaC′).

Washing out by precipitates is the major mechanism for the removal of radioactive pollution from the atmosphere. The distribution of radioactive aerosols that fall from the atmosphere in different areas usually corresponds to the distribution of precipitation. The capture of radioactive aerosols occurs mainly in clouds through the growth of droplets on radioactive dust particles serving as condensation nuclei and through the diffusion capture of the dust particles by drops. The capture of radioactive particles by falling raindrops and snowflakes occurs mainly through the effect of inertial forces and convective diffusion. The concentration of radioactive aerosols in precipitation depends on the type of precipitation, the greatest concentrations occurring in fogs and drizzles.

S. G. MALAKHOV