Application of synchrotron radiation-based techniques (ì-XRD, ì-XRF, and ì-XANES) to study Fe-rich hardpans within waste-rock dump

摘要

Recently, several techniques based on synchrotron radiation have been applied to environmental sciences giving the possibility for non-destructive investigations with micrometer spatial resolution. In particular, a combination of synchrotron methods (ì-XRF, ì-XRD, and ì-XAS) have been undertaken to investigate the metals speciation in mine wastes and soils. With this work, after a review on the mineralogical aspects of sulphide-rich waste-rock deposits and the application of synchrotron-based techniques for their characterization, we present a combined synchrotron-based ì-XRD, ì-XRF, and ì-XANES study to determine the mineralogy and the elemental distribution of metals in partially altered sulphide-mineralization fragments deposited within an open-air waste-rock dump (Libiola mine, eastern Liguria, Italy). The selected samples are composed of heterogeneous assemblages of Fe-bearing precipitates formed as a consequence of Fe-Cu sulphide alteration processes that occur within the main waste rock dump of the mining area. The results evidenced that the authigenic iron-rich phases generally contain significant amounts of hazardous elements such as Cu, Zn, Mo, As, and Se. Moreover, a significant mineralogical control on the mobility of these elements have been observed; in particular, the goethite-rich assemblages show high affinity for Cu and Zn, whereas hematite-rich assemblages selectively concentrate As, Se, Mo, Cu and Zn.