title: Microbial effects on the release and attenuation of arsenic in the shallow subsurface of a natural geochemical anomaly.
abstract: Critical factors leading to arsenic release and attenuation from the shallow subsurface were studied with multidisciplinary approach in the natural gold-arsenic geochemical anomaly at Mokrsko (Czech Republic). The results show that microbial reduction promotes arsenic release from Fe(III) (hydr)oxides and Fe(III) arsenates, thereby enhancing dissolved arsenic in the shallow groundwater at average concentration of 7.76 mg/L. In the organic-rich aggregates and wood particles, however, microbial sulfate reduction triggers the formation of realgar deposits, leading to accumulation of As in the distinct organic-rich patches of the shallow subsurface. We conclude that precipitation of realgar in the shallow subsurface of soil/sediment depends on specific and non-trivial combination of water and rock chemistry, microbial community composition and spatial organisation of the subsurface zone, where speciation in saturated environments varied on a centimeter scale from reduced (decomposed wood, H2S and realgar present) to oxidized (goethite and arsenate minerals are present).
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic. petr.drahota@natur.cuni.cz
authors.forename: Petr
authors.initials: P
authors.lastname: Drahota
authors.forename: Lukáš
authors.initials: L
authors.lastname: Falteisek
authors.forename: Aleš
authors.initials: A
authors.lastname: Redlich
authors.forename: Jan
authors.initials: J
authors.lastname: Rohovec
authors.forename: Tomáš
authors.initials: T
authors.lastname: Matoušek
authors.forename: Ivan
authors.initials: I
authors.lastname: Cepička
mesh_terms: D001151:Arsenic / Q000032:analysis* / Q000378:metabolism; D018153:Czech Republic; D060587:Groundwater / Q000737:chemistry* / Q000382:microbiology; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D014874:Water Pollutants, Chemical; D001151:Arsenic
keywords: Arsenic; Microbial mobilization; Realgar; arrA; dsrB