Low-level analysis of lead-210 in waters via bismuth-210 measurement.

This communication reports the development of an analytical method for the measurement of low-levels of lead-210 in natural waters via measurement of the beta activity of its in-grown bismuth-210 daughter. The analysis essentially consists of three stages. (a) Pre-concentration of the lead-210 in a known volume of water by co-precipitation with a mixed barium/lead sulphate, where the efficiency of the step is determined by gamma measurement of a barium-133 internal tracer. (b) Separation of the in-grown bismuth-210 from its lead-210 parent by solvent extraction of a bismuth carrier into a solution of diethylammonium diethyldithiocarbamate (DDTC) in chloroform. (c) Preparation of a bismuth oxychloride source for gross beta counting to determine the bismuth-210 activity. The reported method is capable of achieving a detection limit (4 sigma b) of < 10 mBq/l.