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dc.contributor.authorHayes, Sarah M
dc.contributor.authorRoot, Robert A
dc.contributor.authorPerdrial, Nicolas
dc.contributor.authorMaier, Raina
dc.contributor.authorChorover, Jon
dc.date.accessioned2019-07-03T23:21:29Z
dc.date.available2019-07-03T23:21:29Z
dc.date.issued2014-09-15
dc.identifier.citationHayes, S. M., Root, R. A., Perdrial, N., Maier, R. M., & Chorover, J. (2014). Surficial weathering of iron sulfide mine tailings under semi-arid climate. Geochimica et cosmochimica acta, 141, 240-257.en_US
dc.identifier.issn0016-7037
dc.identifier.pmid25197102
dc.identifier.doi10.1016/j.gca.2014.05.030
dc.identifier.urihttp://hdl.handle.net/10150/633297
dc.description.abstractMine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130-140 and 100-120 g kg-1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in the lowest pH samples, indicating its metastable persistence in these semiarid tailings. The resulting sharp geochemical speciation gradients in close proximity to the tailings surface have important implications for plant colonization, as well as mobility and bioavailability of co-associated toxic metal(loid)s.en_US
dc.language.isoenen_US
dc.publisherPERGAMON-ELSEVIER SCIENCE LTDen_US
dc.relation.urlhttps://www.sciencedirect.com/science/article/pii/S0016703714003597en_US
dc.rightsCopyright © 2014 Elsevier Ltd. All rights reserved.en_US
dc.subjectQXRDen_US
dc.subjectXASen_US
dc.subjectiron XANESen_US
dc.subjectsemi-arid mine tailingsen_US
dc.subjectsulfur XANESen_US
dc.titleSurficial weathering of iron sulfide mine tailings under semi-arid climateen_US
dc.typeArticleen_US
dc.contributor.departmentUniv Arizona, Dept Soil Water & Environm Scien_US
dc.identifier.journalGEOCHIMICA ET COSMOCHIMICA ACTAen_US
dc.description.note24 month embargo; published online: 5 June 2014en_US
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en_US
dc.eprint.versionFinal accepted manuscripten_US
dc.source.journaltitleGeochimica et cosmochimica acta
refterms.dateFOA2016-06-05T00:00:00Z


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