Input of anthropogenic radionuclides into the World Ocean

Since the early 1940s, when the nuclear era began, the Earth has received anthropogenic radioactive contamination. The main sources have been fallout from nuclear weapons testing in the atmosphere until 1980, discharges from nuclear reprocessing of spent fuel elements from nuclear reactors with maximum releases in the mid-70s and finally the Chernobyl reactor accident which occurred in 1986. As the ocean covers more than 23 of the Earthʹs surface, a substantial part of the radioactive contamination of our planet is to be found in the marine environment. By the year 2000 total inventories of three of the most studied anthropogenic radionuclides in the World Ocean were 0.2 EBq 90Sr, 0.35 EBq 137Cs and 0.01 EBq 239,240Pu. In the case of 137Cs, the contribution from global fallout is 69% of the total inventory, from local fallout, 21%, from reprocessing, 7%, and from Chernobyl, 3%. The most contaminated part of the World Ocean is the NE Atlantic Ocean, which besides fallout from nuclear weapons testing also has received inputs from reprocessing plants and the Chernobyl accident.