Oxidation and mobilization of selenium by nitrate in irrigation drainage

Journal of Environmental Quality



Selenium (Se) can be oxidized by nitrate (NO3) from irrigation on Cretaceous marine shale in western Colorado. Dissolved Se concentrations are positively correlated with dissolved NO3concentrations in surface water and ground water samples from irrigated areas. Redox conditions dominate in the mobilization of Se in marine shale hydrogeologic settings; dissolved Se concentrations increase with increasing platinum-electrode potentials. Theoretical calculations for the oxidation of Se by NO3 and oxygen show favorable Gibbs free energies for the oxidation of Se by NO3, indicating NO3 can act as an electron acceptor for the oxidation of Se. Laboratory batch experiments were performed by adding Mancos Shale samples to zero-dissolved-oxygen water containing 0, 5, 50, and 100 mg/L NO3 as N (mg N/L). Samples were incubated in airtight bottles at 25°C for 188 d; samples collected from the batch experiment bottles show increased Se concentrations over time with increased NO3 concentrations. Pseudo first-order rate constants for NO3 oxidation of Se ranged from 0.0007 to 0.0048/d for 0 to 100 mg N/L NO3 concentrations, respectively. Management of N fertilizer applications in Cretaceous shale settings might help to control the oxidation and mobilization of Se and other trace constituents into the environment.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Oxidation and mobilization of selenium by nitrate in irrigation drainage
Series title Journal of Environmental Quality
DOI 10.2134/jeq1999.00472425002800040019x
Volume 28
Issue 4
Year Published 1999
Language English
Publisher ACSESS
Contributing office(s) Toxic Substances Hydrology Program
Description 6 p.
First page 1182
Last page 1187
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