New Mexico Geological Society Annual Spring Meeting — Abstracts

Uranium is found in numerous deposits in New Mexico and globally. While many uranium deposits have been geochemically characterized, little is known about the effects of wildfire on uranium biogeochemistry in watersheds. With the changing climate in the western United States, wildfire frequency and severity have increased and therefore understanding geochemical changes and ecological risk related to wildfire is increasingly important. Uranium can be found in local bedrock, mines, waste rock, stream sediments, plants, and water, which can all be eroded and transported to streams during storm events after wildfires. Due to uranium’s redox and pH sensitivity, uranium compounds may be geochemically altered during the wildfire or after delivery to water bodies. While the link between wildfires and aqueous uranium has not been extensively explored, after a fire in Portugal, U-238 was identified in vegetation and ash, and during a fire in Idaho, radiation levels in the air spiked around nearby abandoned uranium mines. After the Cerro Grande Fire burned a large area around Los Alamos National Laboratory, an area known for radionuclide resources and legacy radioactive contamination in nearby stream sediments, total uranium concentrations in unfiltered surface water in the region increased one to two orders of magnitude over 4 years. These examples suggest some effects on uranium during and after wildfire. Concepts of potential effects to uranium aqueous and solid phase geochemistry during and after wildfire will be explored. The recent Calf Canyon/Hermit’s Peak fire, in northern New Mexico, burned the Gallinas Creek watershed, which contains several uranium-bearing pegmatite deposits. Ongoing investigations in the Gallinas Creek watershed will apply these concepts.