Speciation and redox chemistry of selenium and arsenic in wetland soils and sediments
Analytical techniques were developed that permitted the determination of selenium and arsenic species commonly encountered in soils and sediments. Under reduced conditions selenium solubility in sediments from Kesterson Reservoir (CA) and Hyco Reservoir (NC) was low and [elemental selenium + selenides] comprised 80-100% of the total soluble selenium. Experimental data and equilibrium thermodynamic calculations suggest that insoluble metal selenides, particularly FeSe, controlled selenium solubility under reduced conditions. Upon oxidation from -200 to 500 mV selenium solubility increased approximately 20 times in both the Kesterson and Hyco Reservoir sediments. Under moderately reduced conditions, selenite was the dominant soluble selenium species. At redox levels above 200 mV, selenite was further oxidized to selenate and selenium solubility reached a maximum. Redox potential and pH were also shown to exhibit a major impact on arsenic speciation, and solubility in Hyco Reservoir (NC) sediments and in an arsenic contaminated soil from Kolin (la). In contrast to selenium, arsenic solubility increased with decreasing redox. In both studies, arsenate was the major arsenic species present under oxidized conditions. Upon reduction, arsenite became the major dissolved arsenic species, and arsenic solubility increased. Upon reduction from 500 to -200 mV, total arsenic in solution increased 25 and 13 times in the Hyco Reservoir and Kolin soil, respectively. The importance of adsorption-desorption and precipitation-dissolution reactions in controlling arsenic chemistry was illustrated in the Kolin soil.
- Research Organization:
- Louisiana State Univ. and Agricultural and Mechanical Coll., Baton Rouge, LA (United States)
- OSTI ID:
- 6914236
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
540320 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
ARSENIC
CHEMISTRY
CONTAMINATION
ELEMENTS
REDOX POTENTIAL
SEDIMENTS
SELENIUM
SEMIMETALS
SOIL CHEMISTRY
SOILS
SOLUBILITY
THERMODYNAMICS