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Elution of Selenium from Contaminated Evaporation Pond Sediments

Dep. of Land, Air, and Water Resour., Veihmeyer Hall, Univ. of California, Davis, CA 95616.

^* Corresponding author.

ABSTRACT

Selenium-contaminated sediments were collected from evaporation ponds at the Kesterson National Wildlife Refuse in California. Columns of undisturbed, freeze-dried, and air-dried sediments were each leached with deionized water, California aqueduct water, and saline water. Total Se and inorganic Se were measured in the effluent. Following leaching, the sediment cores were sectioned, extracts were prepared using deionized water, and analyzed for total Se, inorganic Se, and selenite using fluorimetric techniques. Selenium remained immobile in the undisturbed sediments, but freeze- and air-drying increased Se mobility. The maximum concentrations of total Se in the effluent from undisturbed, freeze-dried, and air-dried sediments were 32, 7600, and 232 650 nmol L^–1, respectively. Microbial activity played an important role in the reduction of Se to immobile and volatile forms. Se recovered in the effluent and from water extraction of the sediments following leaching was highest for deionized water and least for aqueduct water under nonsterilized conditions. The composition of solution did not significantly influence the leaching of Se under sterilized conditions. Introducing Se to previously leached sediments resulted in an increase in water-extractable Se, particularly near the surface. However, when the concentration of added Se was high (31.70 µmol L^–1 in this study), the increase in water-extractable Se also occurred at greater depths in the sediments.

Contribution from Univ. of California, Davis.

Funding was provided by the Univ. of California Salinity/Drainage Task Force.

Received for publication September 8, 1987.