Evidence for the Incorporation of Lead into Barite from Waste Rock Pile Materials

Abstract

Because Pb is one of the most toxic elements and is found as a major contaminant in mining environments, this study aims to identify the distribution of this element in host phases issued from the alteration of mine wastes. The sampling location was a former mine near Oakland, California (USA). This mine was once a source of sulfide minerals from which sulfuric acid was made. The material discussed in this paper was collected in iron hardpans that were formed within the waste rock pile resulting from the excavation work. In most contaminated environments (soils, mine waste), secondary metal-bearing phases arising from alteration processes are usually fine-grained (from 10 µm to less than 1 µm) and highly heterogeneous, requiring the use of micron-scale techniques. We performed microRaman spectroscopy, microscanning X-ray diffraction (SXRD), and microextended X-ray near edge spectroscopy (XANES) to determine the relationships between Pb and a Ba/Fe-rich host phase. Micro-Raman spectroscopy suggests that Pb is preferentially incorporated into barite rather than goethite. Results from micro-Raman experiments show the high sensitivity of this analytical tool to the incorporation of Pb into barite by being especially sensitive to the variations of the S-O bond and showing the characteristic bands due to the contribution of Pb. This association is confirmed and is well-illustrated by micro-SXRD mineral species maps showing the correlation between Pb and barite. Microfocused XANES indicates that Pb is present as Pb 2+ , agreeing with the in situ physicochemical parameters.

Reduction of Se(IV) in Boom Clay: XAS Solid Phase Speciation

“…The occurrence of pyrite in all size fractions is, however, supported by the presence of a Pb L3 edge in the XAS (See SI S3 and S4). The edge energy of 13043 eV suggests a divalent oxidation state as in galena (PbS) which is an impurity, commonly present in natural pyrite samples , .…”

Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses

“…Grain-scale, mineral-metal associations were detected directly using differential X-ray diffraction (Schulze, 1994), and micro-focused methods, including micro-X-ray fluorescence spectroscopy (Manceau et al, 2002; Bernaus et al, 2006; Chorover et al, 2008) and micro-Raman spectroscopy (Skoog et al, 1998). Micro-Raman spectroscopy can detect micrometer sized particles of both crystalline and poorly-crystalline forms, even when the latter are amorphous to X-ray diffraction (XRD) (Filippi et al, 2007; Courtin-Nomade et al, 2008). Despite its potential utility, there have been few prior applications of micro-Raman spectroscopy to mineral identification in mine tailings (Stefaniak et al, 2006).…”

Tracing lake pollution, eutrophication and partial recovery from the sediments of Windermere, UK, using geochemistry and sediment microfabrics

“…Unlike the pure barite crystals in the near surface sediment, the crystals in Unit III consistently contain Pb. The presence of barite-anglesite solid solution has not been reported before from lake sediments and has primarily been associated with mining waste and contaminated soils (Courtin-Nomade et al, 2008;Fernandez-Gonzalez et al, 2013). 4.3.4.…”