INVESTIGATING CONTROLS ON SPATIAL AND TEMPORAL VARIATION OF URANIUM IN GROUNDWATER NEAR AN ABANDONED URANIUM MINE, GRAND CANYON NATIONAL PARK, USA

Uranium mines are found across the western United States, with concerns over their influence on groundwater quality well documented. One major site of interest in relation to this topic is the now defunct uranium mine, Lost Orphan Mine. Groundwater containing the highest concentrations of dissolved uranium on record in the Grand Canyon region are found below this mine, with concentrations soaring to ten times the Maximum Contaminant Level set by the United States Environmental Protection Agency. This research seeks to understand the factors influencing the spatial and temporal variation in dissolved uranium found at springs in the drainage directly below the mine, Horn Creek, and in a neighboring drainage, Salt Creek. 8 groundwater samples near the defunct mine were analyzed for trace metals, major ions, and stable isotopes in early 2023. These modern data in conjunction with historical data sets allow for robust statistical and hydrogeochemical modeling applications that provide insight into uranium’s behavior in groundwater at this site. In understanding the influences on uranium’s behavior in groundwater below this mine, future impacts of mining on groundwater in the region and beyond will be further understood.