2. Ground fallout from radionuclides released during atmospheric testing of nuclear weapons and the Chernobyl accident

Successive passages of air masses contaminated by radioactive aerosols have induced radioactive deposits at ground level. Figure 2 a shows a map of surface activities (Bq.m ^-2 ) due to deposits of caesium 137, strontium 90 and plutonium 239+240 resulting from atmospheric testing of nuclear weapons. Most of this surface activity is the result of American and Soviet tests carried out before 1963. Deposits formed mainly during rainfall