Determination of 210Pb, 226Ra and 137Cs in sediments

A method is described for bringing a sediment sample into solution and subsequently carrying out analysis for ²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs. Silica is removed from the sample by cyclic HNO₃HF treatments. ¹³⁷Cs is separated from ²¹⁰Ra in a carbonate fusion, extracted by absorption on ammonium molybdophosphate, precipitated directly with BiI₃ in presence of citric acid, and β-counted. ²¹⁰Pb and ²²⁶Ra are separated out by 70–75% HNO³ precipitation. Further purification and mutual separation of the two radionuclides is achieved by solvent extraction and anion-exchange techniques. ²¹⁰Pb and ²²⁶Ra are determined by β- and α- counting of their chromate precipitates, respectively, after allowing suitable ingrowth periods for their daughters. The procedural steps effectively eliminate possible interference from other natural or fall-out radioactivities.