Speciation of arsenic in sulfidic waters

Formation constants for thioarsenite species have been determined in dilute solutions at 25[degrees]C, ΣH.sub.2S from 10.sup.-7.5 to 10.sup.-3.0 M, ΣAs from 10.sup.-5.6 to 10.sup.-4.8 M, and pH 7 and 10. The principal inorganic arsenic species in anoxic aquatic systems are arsenite, As(OH).sub.3.s...

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Bibliographic Details
Published in:Geochemical transactions GT 2003-03, Vol.4 (1), p.1-1, Article 1
Main Authors: Wilkin, Richard T, Wallschläger, Dirk, Ford, Robert G
Format: Article
Language:English
Subjects:
Anions
Anoxia
Aquatic environment
Arsenic
Arsenic compounds
Arsenite
Chemical precipitation
Chemical properties
Chemical species
Environmental aspects
Natural environment
Speciation
Sulfate reduction
Sulfates
Sulfides
Sulphate reduction
Sulphides
Surface active agents
Water chemistry
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Summary:Formation constants for thioarsenite species have been determined in dilute solutions at 25[degrees]C, ΣH.sub.2S from 10.sup.-7.5 to 10.sup.-3.0 M, ΣAs from 10.sup.-5.6 to 10.sup.-4.8 M, and pH 7 and 10. The principal inorganic arsenic species in anoxic aquatic systems are arsenite, As(OH).sub.3.sup.0, and a mononuclear thioarsenite with an S/As ratio of 3:1. Thioarsenic species with S/As ratios of 1 : 1,2 : 1, and 4 : 1 are lesser components in sulfidic solutions that might be encountered in natural aquatic environments. Thioarsenites dominate arsenic speciation at sulfide concentrations > 10.sup.-4.3 M at neutral pH. Conversion from neutral As(OH).sub.3.sup.0 to anionic thioarsenite species may regulate the transport and fate of arsenic in sulfate-reducing environments by governing sorption and mineral precipitation reactions.
ISSN:1467-4866
1467-4866
DOI:10.1186/1467-4866-4-1