Co-precipitation methods for transuranics

Pu1 + Pulv fraction Puv + Puvl fraction Concentrations corrected for carry-over (mBq I-1) 

Measured 239/240pu Aliquot (mBqn1) Oxidised tracer co-precipitated (%) Measured 239/240pu (mBqn1) Reduced tracer remaining (%) Pu Pu (reduced) (oxidised) 

Neptunium - Neptunium is known to be present in oxic seawater predominantly as the highly soluble pentavalent species NpOj but, as would seem to be suggested 

Locations Aliquot Concentration of Nplv 237Np species (mBq n1) Npv 237Np v as a percentage of the total 237Np present 

An alternative procedure for the study of neptunium oxidation states at trace concentrations has been described by Inoue and Tochiyama (1977). They showed that, in the pH range 6-7, Nplv may be quantitatively absorbed on silica gel whilst Npv remains in solution. In acid solution, however, a precipitate of barium sulfate selectively absorbs Nplv leaving the higher oxidation states in solution. The authors gave no environmental data for neptunium in their publication but Nelson and Orlandini (1979) subsequendy adapted the procedure to demonstrate that the dominant oxidised plutonium species in natural waters is Puv and not Puvl. 

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