Cosmic ray produced beryllium isotopes in rain water

The two known radioactive isotopes of Beryllium (Be7 and Be10) are produced in the atmosphere in nuclear disintegrations initiated by cosmic radiation. The long lived Be10 (half life 2.7 million years) is difficult to detect and has not yet been isolated. The short lived isotope Be7 (half life 53 days) is easily detected in rain water and should, therefore, be of interest in meteorological studies. The average concentration of Be7 in 8 monsoon rains in Bombay amounted to 2400 atoms per cm3 and is consistent with the production rates predicted by Paters)