Occurrence of 224Ra, 226Ra, 228Ra, gross alpha, and uranium in California groundwater

One hundred and twelve groundwater wells sampled from all the major aquifers in California were analyzed for Ra-224, Ra-226 Ra-228, gross alpha, and uranium. The results showed that radium is found in relatively low concentration, 1.56 X 10(-2)-1.23 Bq L-1 (0.42-33 pCi L-1) for Ra-224, 2.2 X 10(-3)-0.81 Bq L-1 (0.06-22 pCi L-1) for Ra-226, and 8.5 X 10(-3)-1.31 Bq L-1 (0.23-35 pCi L-1) for Ra-228 in California groundwater. Uranium was found at the highest concentration on both mass and activity basis and was correlated with the gross alpha measurement. Short-lived radioisotopes showed no significant contribution to gross alpha measurements. There was a strong correlation between Ra-224 and Ra-228 activities, suggesting the latter to be an indicator for the occurrence of the former. Comparison of Ra-226 to U-238, Ra-224 to Ra-226, and Ra-226 to Ra-228 showed scattered data indicating no correlation between each of these isotope pairs. Approximately 4% of the wells were found to exceed the U.S. Environmental Protection Agency (EPA) established maximum contaminant level for total radium of 0.185 Bq L-1 (5 pCi L-1). Analysis of Ra-228 by gamma-ray spectroscopy was in good agreement with the U.S. EPA-approved procedure.