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

Abstract

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