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GEOREF RECORD

Characterization of arsenic species in microbial mats from an inactive gold mine

Andrea L. Foster and Roger P. Ashley
Characterization of arsenic species in microbial mats from an inactive gold mine (in Metal mining and the environment; Part 2, Rod J. Allan (editor), Arthur J. Horowitz (editor) and Jerry R. Miller (editor))
Geochemistry - Exploration, Environment, Analysis (August 2002) 2, Part 3: 253-261

Abstract

Filamentous cyanobacterial mats and Fe oxyhydroxide-rich bacterial mats collected near an inactive gold mine in California are enriched in arsenic (As) approximately 1000-fold relative to the waters in contact with them. The predominant organism in the cyanobacterial mat could not be identified using morphological characteristics, but the unique morphology of the sheath-forming beta protobacterium Leptothrix ochracea was used to identify this species in Fe oxyhydroxide mat samples from several sites near the gold mine. Leptothrix sheaths commonly exceed 10 mu m in length and have an average diameter of 1 mu m. The Fe-oxyhydroxide mats are dominated by L. ochracea sheaths, but use of fluorescently tagged genetic stains reveals the presence of sheathless bacteria that presumably also promote the formation of Fe oxyhydroxide. X-ray absorption fine structure (XAFS) spectroscopy was used to identify As species in these microbial mats. Mat-associated As is predominantly As(V), even when As(III) is the primary dissolved species in contact with the mats. The species of As(V) associated with the cyanobacterial mat could not be conclusively identified; however, it is not associated with Fe oxyhydroxide or other minerals, based on comparison to XAFS spectra of As adsorbed to various substrates. In addition, the cyanobacterial mat XAFS spectrum is different from that of aqueous As(V), suggesting that As(V) in the mat lacks some or all of the coordinating water molecules present in aqueous solution. We hypothesize that As is associated with the exopolysaccharide (EPS) matrix secreted by the cyanobacteria. In Leptothrix-dominated Fe-oxyhydroxide bacterial mats, XAFS analysis clearly indicates that As(V) is associated with the Fe oxyhydroxide as an adsorbed and/or coprecipitated complex.


ISSN: 1467-7873
EISSN: 2041-4943
Serial Title: Geochemistry - Exploration, Environment, Analysis
Serial Volume: 2, Part 3
Title: Characterization of arsenic species in microbial mats from an inactive gold mine
Title: Metal mining and the environment; Part 2
Author(s): Foster, Andrea L.Ashley, Roger P.
Author(s): Allan, Rod J.editor
Author(s): Horowitz, Arthur J.editor
Author(s): Miller, Jerry R.editor
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Affiliation: Canada Centre for Inland Waters, National Water Research Institute, Burlington, ON, Canada
Pages: 253-261
Published: 200208
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
Meeting name: International Conference on Heavy metals in the environment
Meeting location: Ann Arbor, MI, USA, United States
Meeting date: 20000806Aug. 6-10, 2000
References: 26
Accession Number: 2003-021841
Categories: Environmental geology
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
N32°30'00" - N42°00'00", W124°30'00" - W114°15'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200307
Program Name: USGSOPNon-USGS publications with USGS authors
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