Selenium and salt mobilization in wetland and arid upland soils of Pariette Draw, Utah (USA)

•Hydrology regulates the solubility of Se, S and Fe in soils of an arid land wetland system.•Se distribution in the wetland soils is associated with the distribution of soluble salts.•A sodium selenite-sulfate coprecipitate regulated soil solution Se activity.

Selenium (Se) mobilization in the soils of the Pariette Draw and subsequent accumulation into the Pariette Wetlands threaten wildlife. To gain a better understanding of the soil biogeochemistry of Se in the draw, the physical and chemical properties for two soils in the Pariette Draw located in eastern Utah were compared: one a formerly arid soil (elevation 1448 m) that was flooded following the creation of the wetlands in 1975, and the other an arid soil (elevation 1467 m). The soils were analyzed, and the influence of inundation by irrigation return water of Pariette Draw of Utah was assessed to obtain a better understanding of soil Se and salts in this system. It appears that Se mobility, especially in the wetlands soil, is associated with the distribution of soluble salts in the soil profile. Due to a fluctuating water table caused by a deluge of irrigation return water and high evapotranspiration rates coupled with low precipitation, capillary migration is the dominant mechanism driving the distribution and accumulation of salts and soluble Se in the upper horizons (Byz) of the wetlands soil. The distribution of soluble salts and Se in the upland soil is typical of a downward gravity-driven hydrology process. Gypsum solubility regulated sulfate levels within the Byz horizons of the wetlands soil. We surmise that soluble Se is regulated by the solubility of a sodium selenate sulfate coprecipitate. It appears that the relatively low concentration of Se in the local Pariette Wetlands soil is not the source and cause of Se responsible for adversely affecting wildlife in the wetlands.