A Study of the Factors Affecting the Gross Alpha Measurement and a Radiochemical Analysis of Some Groundwater Samples from the State of Wisconsin Exhibiting an Elevated Gross Alpha Activity

Ninety eight groundwater samples from water utilities from around the state of Wisconsin were analyzed for uranium activity (U-234, U-235, and U-238), thorium activity (Th-228, Th-230, Th-232), radium activity (Ra-226 and Ra-228), polonium-210 activity (Po-210), and gross alpha activity. The gross alpha activity was determined using EPA method 900.0. Many of these groundwater sources were known to have a combined Ra-226 and Ra-228 activity in excess of 5 pCi/L, which is a radium violation according to EPA regulations. Most of these samples contained insignificant amounts of thorium or Po-210. The activity of thorium found in the all of the samples was on the order of 0.1 pCi/L or less. Only two samples contained Po-210 at a level of 1 pCi/L or more. A model was developed to determine the contribution of each radionuclide to the gross alpha activity. An analysis of the factors affecting the gross alpha measurement was conducted using this model.