Sequential determination of isotopes of U, Th, Ra, Pb and /or their activity ratios in environmental water samples

A procedure for sequential determining nine radionuclides of 234U, 238U,, 228Th, 230Th 232Th, 224Ra, 226Ra, 228Ra and 210Pb and/or their activity ratios in a same water sample is described. Five litres of water sample is acidified with HCl, and U, Th and Ra, Pb are concentrated by Fe(OH)3 and sulfate respectively. The concentrated U and Th are further separated in a TBP-teflon support column followed by electrodeposition and α-counting. After the BaSO4 is reprecipitated for separating isotopes of Ra from EDTA solution, adjust the pH to 2.0, then most of interferences are cleaned away through the crystallization of excessive EDTA itself. Finally add Fe2(SO4)3 to EDTA solution for precipitation of PbSO4. The β-emitter, 210Bi, daughter of 210 Pb, in the precipitate is measured several days later. The decontamination factor between Ra and Pb themselves is over 1000. 0.5g/L of calcium concentration can be tolerated. The detection limits for U, and Th are lμg/L and 3μg/L, for 224Ra, 226Ra, 228Ra and 210Pb, 2.5 x 10-2, 8 x 10-3, 4 x 10-3 and 5 x 10-3Bq/L respectively