Affiliation:
1. Wisconsin State Laboratory of Hygiene Madison Wisconsin USA
2. Environmental Chemistry and Technology Program, Department of Civil and Environmental Engineering University of Wisconsin‐Madison Madison Wisconsin USA
Abstract
AbstractUranium is a regulated contaminant (maximum contaminant level [MCL] 30 μg/L) that contributes to the gross alpha activity of groundwater. The adjusted gross alpha activity (MCL 15 pCi/L) is determined by subtracting the total uranium activity from the measured gross alpha activity. U.S. water utilities can use mass‐based and radiochemical analysis methods for compliance monitoring of uranium. Mass‐based measurements use a conversion factor of 0.67 pCi/μg of uranium to calculate the adjusted gross alpha activity. This conversion factor assumes that the activity of 234U equals 238U. Here, we present two decades of uranium isotope data measured by alpha spectrometry that shows 234U activity typically exceeds 238U. Using mass‐based measurements, the total uranium activity is biased low causing artificial exceedances of the adjusted gross alpha activity. Therefore, water utilities with gross alpha activities >15 pCi/L should utilize radiochemical analyses for uranium for the most accurate calculation of adjusted gross alpha activity.
Subject
Water Science and Technology,Environmental Engineering,General Chemistry,Filtration and Separation