Bare Soil Evaporation and Solute Movement in Selenium-Contaminated Soils of Kesterson Reservoir
1992
Zawislanski, Peter T. | Tokunaga, Tetsu K. | Benson, Sally M. | Oldfather, Joan M. | Narasimhan, T.N.
Two approaches were taken to estimate evaporation of water from the surface of a salt-encrusted and Se contaminated soil in a playalike environment at Kesterson Reservoir, California. Direct evaporation flux measurements were made using a lysimetric (gravimetric) approach and revealed a seasonal dependence of bare soil evaporation rates, which ranged from 0.1 to 1.5 mm d⁻¹. The low range is suggestive of a vapor-flux control of bare soil evaporation due to the presence of a salt crust. Temporal changes in chloride concentrations and soil moisture content were used in a quantitative assessment of a mean seasonal evaporative flux. Bare soil evaporation rates measured by these two methods compared favorably. Although concentrations of salts and Se in near-surface soil fluctuated seasonally during a drier than average year, a slight net decline in salt concentrations was observed over 12 mo due to rainfall infiltration and the associated solute transport. Increases in Se near the soil surface due to an evaporatively driven flux appear unlikely in this setting, due to low rates of bare soil evaporation as compared with downward fluxes due to rainfall infiltration.
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