Abstract
The measurements of the oxidation states of fallout plutonium in rain water collected at Monaco indicate that plutonium exists predominantly in the higher oxidation states (Pu (V) and Pu (VI)). The results obtained show that the percentage of the higher valency fraction of plutonium ranges from 38 to 89 % of the total soluble plutonium in rain. The percentage tends to be lower when the storage time before the chemical treatment becomes longer. A thermodynamical computation supports these findings. The occurrence of plutonium in the higher oxidation states in rain is considered to be one of the major causes of the characteristic geochemical stability of fallout plutonium observed in the Mediterranean Sea.
