Investigation of Mineralogical Properties and Arsenic Speciation in Soils from an Abandoned Gold Mine Using Synchrotron-Based X-ray Techniques

This study investigates the mineralogical and chemical properties of arsenic-contaminated soils from an abandoned gold mine in South Korea, utilizing a combination of synchrotron-based X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and conventional analytical techniques.Quantitative XRD (QXRD) results indicate that the soils are primarily composed of quartz and mica, with varying contents of dolomite, talc, and chlorite depending on particle size.These QXRD findings are strongly supported by polarizing microscopy, which visually confirmed mineral occurrences, and by X-ray fluorescence (XRF) analysis, which revealed consistent elemental compositions.XAS analysis revealed that arsenic predominantly exists in the form of scorodite (FeAsO 4 2H 2 O), along with minor fractions of arsenopyrite (FeAsS) and adsorbed arsenate species.High arsenic concentrations, particularly in fine particles (<75 m), raise concerns for potential environmental dispersion via wind and water erosion.Additionally, the study confirms that under slightly alkaline conditions (pH 8.1), arsenate species readily leach from soil, indicating limited natural attenuation in the studied area.The findings emphasize the need for effective containment strategies, and highlight the utility of synchrotron X-ray techniques in environmental geoscience for understanding contaminant behavior at a molecular level.