Geochemical and Advanced Electron Microscopical Characterisations of Artisanal Gold Mining Rejects in Colombia

Abstract

Artisanal gold mining causes widespread health problems due to illegal exposure to hazardous inorganic compounds, such as arsenic (As) and mercury (Hg). The sources and prevalence of mining pollution are strongly influenced by topography, stream dynamics, soil type, and land use. In the present study, the potential hazardous elements (PHEs), absorption abilities of nanoparticles (NPs), and ultrafine particles (UFPs) were analysed from clandestine gold mining soils in Colombia. The proportions of PHEs including As, Hg, Cu, Cr, and Pb in carbonates, sulfides, clays, oxides, hydroxides, and sulfates were determined by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED)/micro-beam diffraction (MBD)/energy dispersive X-ray spectroscopy (EDS). The results revealed that the concentrations of As, Hg, and Zn were significantly higher in clay particles when compared to the other soil samples. Furthermore, Al and Fe manifested excellent PHEs sorption abilities in the artisanal gold mining soils. The results presented will be useful for future mitigation measures in the gold mining areas.