Arsenic Forms in Soils of Various Settings in the Historical Ore Mining and Processing Site of Radzimowice, Western Sudetes

This study, carried out in Radzimowice, a historical As mining site, analyzed the speciation and mineralogical As forms in soils, in different locations, as related to rock weathering processes and associated environmental risk. Four soil groups, including those on mine dumps, and in the stream valley, as well as stream sediments, were examined. The screening performed on 52 samples showed an extremely low actual As solubility, except for soils at reducing conditions. Nine samples were subjected to mineralogical analysis by microscopy and X-ray diffraction (XRD), and sequential extraction according to Wenzel. The results indicated that in all samples, As was associated mainly with amorphous Fe oxides, that constituted up to 66% of total As. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) analysis performed on 3 representative samples revealed that the dump material contained the grains of primary As minerals, mainly arsenopyrite and loelingite, rimmed and encrusted with goethite. Stream sediments and the alluvial soil contained large amounts of (hydroxy)Fe-oxides, in which As was present in sparse scorodite grains and in highly dispersed forms associated with goethite and amorphous compounds of various compositions. The diversity of As species makes forecasting of its environmental fate difficult, therefore further research should focus on As transformations, particularly under reducing conditions.