Surficial weathering of iron sulfide mine tailings under semi-arid climate
AffiliationUniv Arizona, Dept Soil Water & Environm Sci
MetadataShow full item record
PublisherPERGAMON-ELSEVIER SCIENCE LTD
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.
JournalGEOCHIMICA ET COSMOCHIMICA ACTA
RightsCopyright © 2014 Elsevier Ltd. All rights reserved.
Collection InformationThis 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 email@example.com.
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.
Note24 month embargo; published online: 5 June 2014
VersionFinal accepted manuscript
- Toxic metal(loid) speciation during weathering of iron sulfide mine tailings under semi-arid climate.
- Authors: Root RA, Hayes SM, Hammond CM, Maier RM, Chorover J
- Issue date: 2015 Nov 1
- Changes in zinc speciation with mine tailings acidification in a semiarid weathering environment.
- Authors: Hayes SM, O'Day PA, Webb SM, Maier RM, Chorover J
- Issue date: 2011 Sep 1
- Geochemical weathering increases lead bioaccessibility in semi-arid mine tailings.
- Authors: Hayes SM, Webb SM, Bargar JR, O'Day PA, Maier RM, Chorover J
- Issue date: 2012 Jun 5
- Geochemical and mineralogical characterization of a neutral, low-sulfide/high-carbonate tailings impoundment, Markušovce, eastern Slovakia.
- Authors: Hiller E, Petrák M, Tóth R, Lalinská-Voleková B, Jurkovič L, Kučerová G, Radková A, Sottník P, Vozár J
- Issue date: 2013 Nov
- Oxidative weathering decreases bioaccessibility of toxic metal(loid)s in PM<sub>10</sub> emissions from sulfide mine tailings.
- Authors: Thomas AN, Root RA, Lantz RC, Sáez AE, Chorover J
- Issue date: 2018 Apr