Determination of 210Pb and 210Po in soil or rock samples containing refractory matrices.

A new method has been developed for determination of (210)Pb and (210)Po in soil or rock samples containing refractory matrices. The samples were first fused with Na(2)CO(3) and Na(2)O(2) at 600 degrees C for pre-treatment and then (210)Pb and (210)Po were sequentially leached out at 200-250 degrees C with HNO(3)+HF, HClO(4) and HCl. About 10% of the leaching solution was used for (210)Po determination, carried out by spontaneous deposition of polonium on a silver disc from a weakly acidic solution that contained hydroxylamine hydrochloride, sodium citrate and (209)Po tracer, measurement being made by alpha-spectrometry. The remains of the leaching solution were used for determination of (210)Pb, conducted by precipitation as sulphate, purification with Na(2)S as PbS in 6M ammonium acetate, separation from alpha-emitters by an anion-exchange resin column, source preparation as PbSO(4), and measurement with a beta-counter. The procedure has been checked with two certified IAEA reference materials, showing good agreement with the recommended values. The lower limits of detection for 1g of analysed soil or rock samples were found to be 0.75 Bqkg(-1) for (210)Po and 2.2 Bqkg(-1) for (210)Pb. A variety of solid sample species analysed through use of the procedure gave average yields of 90.0+/-9.8% for (210)Po and 88.4+/-7.1% for (210)Pb.