An Alternative Method for the Determination of Excess 210Pb in Sediments

Abstract

Nowadays, there are several multidetector low-level proportional counters on the market, which are able to measure up to 16 samples simultaneously. Such counters are particularly useful for ²¹⁰Pb dating, when a core is split into many samples to be analysed. In order to preserve this advantage, a simple radiochemical method should be applied for atmospheric, or excess, ²¹⁰Pb prior to its determination by beta counting. Starting from a 0.5 M HBr leaching step, a simple chemical separation scheme based on anionic ion exchange was developed. In this method, the lead present in the eluate is precipitated as lead chromate and the ²¹⁰Pb is determined through the beta counting of ²¹⁰Bi. The application is discussed of the above chemical separation procedure to marine sediment reference samples, IAEA 368 and IAEA 135, as well as to sediment cores from different environments. Using 5 g of dry sediment sample and 24,000 s counting time, a detection limit of 3 mBq.g^-1 can be achieved.