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

A method for speciation and determination of Pb-210 and Po-210 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 degrees C and pH 1.5, and Po-210 was measured by alpha-spectrometry; the remain solution was used to separate lead by anion-exchange resin and purified by precipitation as PbS and PbSO4, and Pb-210 was determined by a low background beta-counter. The IAEA-327 reference material (soil) was studied for Pb-210 and Po-210 speciation. The results show that: (1) the average yields are 88.7 +/- 6.4% for Pb-210 and 93.8 +/- 8.2% for Po-210; (2) if compared to the total Pb-210 activity in the sample, Pb-210 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 Po-210 are 0.17%, 0.97%, 21.0%, 0.47% and 77.4%. respectively; and (3) the obtained Pb-210 concentration is in good agreement with the recommended value given by the IAEA. (c) 2006 Elsevier B.V. All rights reserved.