The fractionation and determination procedures for the speciation of 210Pb and 210Po in soil samples

Abstract A method for speciation and determination of 210 Pb and 210 Po in soil samples was developed. The speciation was carried out by fractionating the soil samples into five fractions which are water soluble or exchangeable, bound to carbonates, bound to Fe–Mn oxides, bound to organic matter and bound to residue. After mineralisation, 10% solution of each fraction was used to spontaneously deposit polonium on a silver disk at 85–90 °C and pH 1.5, and 210 Po was measured by α-spectrometry; the remain solution was used to separate lead by anion-exchange resin and purified by precipitation as PbS and PbSO 4 , and 210 Pb was determined by a low background β-counter. The IAEA-327 reference material (soil) was studied for 210 Pb and 210 Po speciation. The results show that: (1) the average yields are 88.7 ± 6.4% for 210 Pb and 93.8 ± 8.2% for 210 Po; (2) if compared to the total 210 Pb activity in the sample, 210 Pb fractions are 0.95% in exchangeable form, 10.6% bound to carbonates, 14.3% bound to Fe–Mn oxides, 7.0% bound to organic matter and 67.2% bound to residue or acid soluble, and the corresponding values for 210 Po are 0.17%, 0.97%, 21.0%, 0.47% and 77.4%, respectively; and (3) the obtained 210 Pb concentration is in good agreement with the recommended value given by the IAEA.