Selenium Mobilization from Shales

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. Since 1985 programs In the upper Colorado River Basin 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.