| Popis: |
The Pariette Wetlands was constructed to provide wildlife habitat in an arid environment. Elevated levels of selenium (Se) have been detected in water, soil, and biota. Selenium concentrations have ranged from below detection limit to four times the water quality criterium limit. Here we report on three interrelated research topics: 1) selenium mass balance and flux in water, 2) selenium accumulation, concentration and volatilization of water and plant tissues; and 3) selenium sorption by upland and wetlands soils. 1) Mass balance and mass water flux of selenium for the Pariette Wetlands were studied. A comparison of inlet and outlet Se fluxes was used to determine the mass of Se stored. Selenium concentrations were higher at the inlet (2.1-16.3 μg L-1) than at the outlet (2.0-14.0 μg L-1). The average amount of Se retention and/or loss was 75%. 2) Elevated levels of selenium (Se) in water, soil, and biota of the Pariette Wetlands, Utah. Twelve sample sites were selected to determine the spatial and temporal variation of Se accumulation, concentration and volatilization. At the inlet, concentrations of waterborne Se during low-flow period (winter) were significantly higher than concentrations during high-flow irrigation season (summer). Se concentrations in water at the outlet were lower during the high-flow period ranging from. In contrast, plant tissue Se concentration was lower at the inlet and higher at the outlet. Selenium volatilization results indicated that there were spatial and temporal differences among samples sites. 3) The physical and chemical properties were compared for two soils in the Pariette Draw of Utah. It appears that Se mobility is associated with the distribution of soluble salts. We surmise that soluble Se is regulated by the solubility of a sodium selenate sulfate coprecipitate.. Knowledge gained about the mass balance, storage of Se, and the associated biogeochemical processes in water, plants, and soils that contribute to the accumulation or loss of Se in the wetlands will be beneficial to future land management decisions to minimize the impact of Se exposure to wildlife. |
