HR: 17:05h
AN: B44A-04    [Abstracts]
TI: Dissolution Kinetics of Arsenopyrite in the Presence of Iron(III)-Sequestering Biogenic Ligands at pH 5.
AU: * Cornejo-Garrido, H
EM: cghgill@yahoo.com.mx
AF: Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: * Cornejo-Garrido, H
EM: cghgill@yahoo.com.mx
AF: Instituto de Geografia, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Fernandez-Lomelin, P
EM: pilarf@igg.unam.mx
AF: Instituto de Geografia, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Guzman-Mendoza, J
AF: Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Sedov, S
EM: sergey@geologia.unam.mx
AF: Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AU: Cervini-Silva, J
EM: jcervini@igg.unam.mx
AF: Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan, Mexico City, 04510, Mexico
AB: Arsenopyrite is one of the most important natural sources of Arsenic on Earth. Arsenopyrite is relatively insoluble in pure water. That is not the case if it is exposed to environmental conditions. Notably, arsenopyrite surfaces exposed to biological activity undergo changes in lattice energy, surface morphology, particle size, and other properties, typical of mineral dissolution. Iron biogeochemical cycling is pivotal to electron transferring in nature. Therein, the need to further scrutinize on the mechanism of arsenopyrite dissolution induced by biological activity. In oxic environments, such as highly weathered soils or surficial seawater, microorganisms and higher plants produce biogenic ligands such as siderophores to mobilize Fe that otherwise would be unavailable. Siderophores ligands facilitate the dissolution of natural particles that represent a primary reservoir of iron. In this paper we study the stability of arsenopyrite in the presence of desferrioxamine (DFO-B), a common siderophore ligand, at pH 5. Arsenopyrite specimens from mines from Panasqueira, Portugal, were used for this study. Batch dissolution experiments of arsenopyrite (1 g L-1) in the presence of DFO-B ([DFO-B]0 ƒ¬ 200 ƒÝM) were conducted for 7 days. The initial pH was adjusted to 5. Samples were stirred at 150 rpm. Sieving was conducted to homogeneized the particle size 0.149-0.1mm before conducting the dissolution experiments. Corresponding experiments in the absence of DFO-B for the purpose of comparison were also conducted. Analyses for soluble metals were conducted by AA and ICP-AES. Surface characterization was conducted by XRD and SEM-EDX. Incrustations of Pb(0) were detected in the arsenopyrite samples used for this study. In the presence of DFO-B, releases of Fe, As, and Pb showed positive trends with time. A shallower dependency was observed for release of Fe, As, and Pb in the presence of water only under similar experimental conditions. Detected concentrations of Fe, As, and Pb, after 100 h of reaction time in the presence of DFO-B were 0.3, 0.26, and 0.13 ƒÝM, respectively. Concentrations of Fe, As, and Pb, in the presence of water only were ca. 0.06, 0.13, and 0.01 ƒÝM, correspondingly. Hence, the effectiveness of DFO-B for releasing Pb was almost three times higher than that for releasing Fe (further details on Pb dissolution as affected by DFO-B are provided in Cornejo et al.). These results cannot be accounted for by size¡Xto-charge considerations prevailing in metal complexation by DFO-B only. Elemental sample enrichment as evidenced by SEM-EDX supporte the idea the Fe-S subunit bond energy is limiting for Fe release, while likely, the mechanism(s) of dissolution for Pb is independent and occurs concurrently to than for Fe and As.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0448 Geomicrobiology
DE: 0456 Life in extreme environments
SC: Biogeosciences [B]
MN: 2007 Joint Assembly