Tritium inventory of the Black Sea

Tritium and helium-3 measurements from the southern half of the Black Sea are described. A tritium maximum centered at approximately 1200 m and accompanied by a radiogenic helium-3 maximum suggests deep injection of near surface water in the eastern part of the basin. The results are combined with three other tritium data sets to discern the temporal variation in the past three decades. The observed temporal variation is slower than would be expected from radioactive decay alone in the upper few hundred meters where the major proportion of tritium resides. This trend suggests that there must have been a tritium source(s) other than that produced by the atmospheric nuclear tests. It is estimated that approximately 0.1 kg of tritium of non-atmospheric origin had entered the Black Sea since 1969.