Selenium Mobilization from Shales
Science Center Objects
Selenium (Se) and salinity (total dissolved solids) are water-quality concerns in much of the arid western US where agricultural and urban irrigation overlie Cretaceous-age shale. Leaching of Se and salinity from shale can degrade water quality and negatively affect aquatic biota in receiving water bodies. In the upper Colorado River Basin, programs since 1985 have worked to reduce Se and salinity loads to the Colorado River through implementation of best management practices; however, there is still a lack of understanding of how periodic recharge (wetting and drying) control mobilization of Se and salinity from shale. Monitoring results also indicate statistical relations between dissolved nitrate and Se concentrations, suggesting that nitrate may play an important role in Se mobilization.
This study has evaluated physical and chemical processes controlling Se and salinity mobilization from shales in the upper Colorado River Basin. Specific research questions addressed by this study include:
- How do recharge and water-table fluctuations (wetting and drying) affect the mobilization of Se and salinity from shales?
- How does the presence of dissolved nitrate in groundwater affect Se mobilization from shales?
Loutzenhizer Arroyo, a tributary of the Uncompahgre River, has some of the greatest Se concentrations in the river basin
(Public domain.)
Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA
Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic...
Mills, Taylor J.; Mast, Alisa; Thomas, Judith C.; Keith, Gabrielle L. Mobilization of selenium from the Mancos Shale and associated soils in the lower Uncompahgre River Basin, Colorado
This study investigates processes controlling mobilization of selenium in the lower part of the Uncompahgre River Basin in western Colorado. Selenium occurs naturally in the underlying Mancos Shale and is leached to groundwater and surface water by limited natural runoff, agricultural and domestic irrigation, and leakage from irrigation canals....
Mast, Alisa; Mills, Taylor J.; Paschke, Suzanne S.; Keith, Gabrielle; Linard, Joshua I.