1 research outputs found
Selenium Speciation in Coal Ash Spilled at the Tennessee Valley Authority Kingston Site
Selenium (Se) in
coal ash spills poses a threat to adjacent ecosystems
because of its potential to mobilize and bioaccumulate in aquatic
organisms. Given that the mobility and bioavailability of Se is controlled
by its valence states, we aimed to define Se speciation in coal ash
solids and examine the relationships between Se speciation and the
magnitude of its mobilization from coal ash. We used coal ash samples
from the Tennessee Valley Authority (TVA)-Kingston fossil plant and
the site of a coal ash spill that occurred in 2008 in Tennessee. Results
of X-ray absorption spectroscopic analyses showed that Se in coal
ash samples was a mixture of elemental Se<sup>0</sup> and Se oxyanions.
The amount of leachable Se increased with an increase of pH from 3
to 13. At the natural pH of coal ash samples (from pH 7.6 to 9.5),
the leachable Se was comprised of Se oxyanions, mainly selenite. This
was observed by both direct quantification of Se oxyanions in the
leachate and the corresponding loss of Se oxyanions in the solid phase.
At pH 12, however, the Se release appeared to derive from both desorption
of Se oxyanions and oxidative dissolution of elemental Se<sup>0</sup>. Our results indicate that Se oxyanions are the most labile species;
however, the magnitude of Se mobilization will increase if the waste
material is subjected to alkaline conditions