Relationship between radioactivity of radium and concentrations of barium and lead in hokutolite

Hokutolite consists of barite (BaSO4) and anglesite (PbSO4), and contains significant amounts of radium isotopes as a radioactive mineral. Photon activation and gamma-ray spectrometry were employed to determine Ba, Pb and 226Ra contents in hokutolite samples and to investigate the correlation between 226Ra activity and both Ba and Pb content. 226Ra activity in 30 hokutolite samples were estimated in the range of 40-65 Bq/g and was positively related to Ba content (r=0.859, p<0.001), but independent of Pb content (r=−0.236, p=0.217). Experimental results implied that 226Ra preferably precipitated with Ba over Pb. The 226Ra activity in hokutolite from the Peitou Hot Spring was experimentally estimated based on the Ba/Pb ratio and expressed as 226Ra (Bq/g)=14.67 (Ba/Pb)molar+14.13.