The importance of uranium isotope composition for gross alpha activity regulation

Uranium is a regulated contaminant (maximum level [MCL] 30 μg/L) that contributes to the gross alpha activity of groundwater. The adjusted (MCL 15 pCi/L) determined by subtracting total uranium from measured activity. U.S. water utilities can use mass-based and radiochemical analysis methods for compliance monitoring uranium. Mass-based measurements conversion factor 0.67 pCi/μg calculate This assumes 234U equals 238U. Here, we present two decades isotope data spectrometry shows typically exceeds Using measurements, biased low causing artificial exceedances Therefore, with activities >15 pCi/L should utilize analyses most accurate calculation