USGS scientists completed a comprehensive hydrologic and geochemical study on 37 springs discharging from rock formations north of the Grand Canyon to establish baseline concentrations for nine naturally occurring elements, some of which may be associated with uranium mining in the area (arsenic, boron, lithium, selenium, silica, strontium, thallium, uranium, and vanadium). Spring water was sampled owing to the lack of wells, which was due in part to the remoteness and depths to groundwater of more than 3,000 feet in some areas. Spring water geochemistry represents a snapshot of past conditions based on the age of the water and the contribution of water of different ages.
Although most of the spring sites had uranium concentrations less than 10 micrograms per liter, six springs had concentrations greater than that level, which is considered anomalous in the area. Comprehensive geochemical and hydrologic analyses were done to determine if these elevated concentrations were coincident with mining or representative of natural sources. The geochemical characteristics of the six springs with elevated uranium concentrations include near-neutral pH, high specific conductance, and similar geochemical signatures, indicating they contain a mixture of modern and pre-modern waters. Similar geochemical compositions of spring waters with high levels of uranium are observed at sites located near and far from uranium-mining activities in the present study. Lines of evidence examined in this study suggest that the uranium in these six springs is likely from natural sources and therefore not likely related to nearby uranium mining.
Objective
Establish baseline concentrations for nine naturally occurring elements, some of which may be associated with uranium mining in the area (arsenic, boron, lithium, selenium, silica, strontium, thallium, uranium, and vanadium) in 37 springs discharging from rock formations north of the Grand Canyon.
Completed
Task 8a: Continue evaluation/analysis of Uranium Activity Ratio analysis
Kimberly Beisner
Hydrologist
Arizona and New Mexico Water Science Centers
505.830.7945
kbeisner@usgs.gov
