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

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.