text: In this field, the following directions were developed in V. G. Khlopin's works: 
  1. radioelements migration, in particular - relatively short-lived in the Earth's crust; 
  2. study of radium-mesothorium containing waters; 
  3. Determination of geologic age on the basis of radioactive data; 
  4. distribution of helium and argon in natural gases of the country; 
  5. effects of natural waters in geochemistry of noble gases; 
  6. distribution of boron in natural waters.