ABSTRACT
Radium has three naturally occurring isotopes that are of concern in groundwater used for drinking water supply. These are 226Ra (t 112 = 1600 years), 228Ra (t112 = 5.7 years), and 224Ra (t 112 = 3.64 days). 226Ra is an alpha emitter in the 238 U decay chain; its immediate daughter is 222Rn, an alphaemitting inert gas easily transferred from water to air, where it has a potential to cause lung cancer. 228Ra is a beta emitter in the 232Th decay chain; its secondgeneration daughter is 224 Ra, an alpha emitter that is expected to be present in groundwaters that contain its progenitor, 228Ra. Aging a radium-contaminated groundwater for 21 days has no effect on the presence of 226Ra or 228Ra but will virtually eliminate the presence of the short-lived alpha-emitting 224Ra, and result in a lowering of the radium and gross alpha contamination in the water. 1
Chemically, the isotopes of radium are indistinguishable. Thus, removing 90% of 226Ra also means removing 900Jo of 228Ra, a helpful fact when monitoring treatment processes for total radium removal because 226Ra analysis is easier and less expensive than 228Ra analysis.
