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.