Date of Award
Master of Science (MS)
Naturally occurring radon in groundwater was used to test radon mixing models. Two different mixing models were used to quantify groundwater fluxes to streams; an analytical solution and a finite difference method. Two different bodies of waters were used in this study. The first location was Johnson Creek located in Grant-Kohrs Ranch in Deer Lodge, Montana. This is a small creek where lots of sampling points were taken. The stretch of Johnson Creek where radon samples were collected was about 0.34 km long with a flowrate between 0.01 m3/s and 0.017 m3/s. The second location was Merced River located in Yosemite Valley (Yosemite National Park) in the state of California. This is a much larger river compared to Johnson Creek, and also had fewer sampling points. The reach looked at in this study is from Happy Isles to Pohono Bridge, a 17.3 km distance with a flowrate that ranges between 0.20 m3/s and ~120 m3/s at Happy Isles depending on the time of the year. To test the models, both bodies of water were known to have groundwater gains meaning that back calculations for gas exchange values could be derived. The finite difference method was found to have errors that are still undetermined. The average gas exchange values for radon in the analytical model tested were between 154.6 day-1 to 195.6 day-1 for Johnson Creek and 2.7 day-1 to 3.5 day-1 for Merced River. Johnson Creek’s gas exchange values for radon compare well to published sites. Merced River gas exchange values for radon are low in comparison to past studies on gas exchange; this could be due to the long reach with few sampling points.
Machinal, Mandy, "USING NATURALLY OCCURRING RADON 222 AS A TRACER TO QUANTIFY GROUNDWATER FLUXES TO STREAMS" (2016). Graduate Theses & Non-Theses. 82.