Selenium speciation in ground water
Selenium toxicity diseases in animals may occur when the intake exceeds 4 mg/kg and selenium deficiency symptoms may occur when dietary intake is less than 0.04 mg/kg. Since the selenium dietary requirement is very close to toxic concentration, it is important to understand the distribution of selenium in the environment. Selenium occurs in four oxidation states (-II, 0, +IV, and +VI) as selenide, elemental selenium, selenite and selenate. Selenate is reported as more soluble and less adsorbed than selenite. Selenate is more easily leached from soils and is the most available form for plants. Increased mobility of Se into the environment via anthropogenic activities, and the potential oxidation-reduction behavior of the element have made it imperative to study the aquatic chemistry of Se. For this purpose, Se species are divided into two different categories: dissolved Se (in material that passes through filters with 0.45 u openings) and particulate Se (in material of particle size > 0.45 mm) typically suspended sediment and other suspended solids. Element and colloidal phase, not truly dissolved, but passing through the filter is deemed to consist of selenium (-2,0). In dissolved state selenium may exist in three of its four oxidation states; Se(-II), Se(+IV), and Se(+VI). Particulate Se may exist in the same oxidation states as dissolved Se and can be found in different phases of the particulate matter. In sediments, Se may be within the organic material, iron and manganese oxides, carbonates or other mineral phases. The actual chemical forms of Se may be adsorbed to or coprecipitated with these phases (primarily selenite, SeO{sub 3}{sup 2{minus}}) and selenate, SeO{sub 4}{sup 2{minus}}. Selenide, Se(-II), can be covalently bound in the organic portion of a sediment. In addition, Se may be found in anoxic sediments as insoluble metal selenide precipitates, an insoluble elemental Se or as ferroselite (FeSe{sub 2}) and Se containing pyrite.
- Research Organization:
- Oklahoma Univ., Norman, OK (United States). School of Civil Engineering and Environmental Science
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-89PC89782
- OSTI ID:
- 7107624
- Report Number(s):
- DOE/PC/89782-T8; ON: DE92018429
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
ANIMALS
AVAILABILITY
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMICAL STATE
CHEMISTRY
CHROMATOGRAPHY
DATA
DEVELOPED COUNTRIES
DIAGRAMS
DISSOLUTION
DISTRIBUTION
DOCUMENT TYPES
ECOLOGICAL CONCENTRATION
ELEMENTS
EXPERIMENTAL DATA
FEDERAL REGION VI
GROUND WATER
HYDROGEN COMPOUNDS
INFORMATION
INTAKE
LEACHING
LIQUID COLUMN CHROMATOGRAPHY
NORTH AMERICA
NUMERICAL DATA
OKLAHOMA
OXIDATION
OXYGEN COMPOUNDS
PH VALUE
PHASE DIAGRAMS
PLANTS
PROGRESS REPORT
REDUCTION
SELENATES
SELENIDES
SELENITES
SELENIUM
SELENIUM COMPOUNDS
SEMIMETALS
SEPARATION PROCESSES
SOILS
SPATIAL DISTRIBUTION
TOXICITY
USA
WATER
WATER CHEMISTRY