Anthropogenic influence on groundwater geochemistry in Horn Creek Watershed near the Orphan Mine in Grand Canyon National Park, Arizona, USA

Groundwater near the Orphan Mine in Grand Canyon National Park shows significant uranium concentration reductions, suggesting interaction with mineralized breccia pipe deposits. Uranium levels drop by an order of magnitude from bedrock to alluvial material, supported by low sulfur and uranium isotopic ratios. Per- and polyfluoroalkyl substances were detected at low concentrations, hinting at possible mining-related contamination. PHREEQC modeling indicates mixing of uranium-rich groundwater with other sources, including modern water influenced by Orphan Mine workings, as evidenced by elevated tritium levels. This study provides evidence of anthropogenic influence on groundwater geochemistry in the Horn Creek Watershed.

Beisner, K. R., Davidson, C., & Tillman, F. (2023). Anthropogenic influence on groundwater geochemistry in Horn Creek Watershed near the Orphan Mine in Grand Canyon National Park, Arizona, USA. Geochemistry: Exploration, Environment, Analysis, 23(3). https://doi.org/10.1144/geochem2023-007