Evidence of Colloidal pyrite transport in soils developing on historic coal mine spoils

First Author's Department

Department of Geology

Second Author's Department

Department of Geology

Third Author's Department

Department of Geology



Document Type



Historic coal mines are one of the major generators of Acid Mine Drainage (AMD) in the United States. Past coal mining activities in Huff Run, Ohio generated large mine spoils and oxidation of these mine spoils led to a serious AMD generation in the Huff Run watershed. A remediation project conducted in the Huff Run watershed costing over $590,000 failed to resolve AMD generation. The persistent AMD generation could be associated with the possible formation, transportation and oxidation of colloidal pyrite from mine spoils. To investigate the transport of colloidal pyrite through unsaturated soil in Huff Run subwatershed HR#25, eight lysimeters were installed and pore water samples were collected during summer of 2018. Initial studies have indicated the presence of colloidal pyrites in the porewater. The scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) analysis of the colloidal particles isolated from pore water samples revealed the presence of iron (Fe), sulfur (S) and oxygen (O) bearing phases in the colloids which are consistent with pyrite (FeS2) and the oxidation product Fe oxides. The x-ray diffraction (XRD) analysis of the colloidal samples confirmed the presence of multiple phases of sulfide bearing minerals (FeS2, FeAsS2, CuFeS2). Both SEM-EDS and XRD detected the presence of Fe oxides associated with colloidal pyrite which can have a significant environmental impact in terms of colloidal pyrite oxidation, AMD generation and trace metals adsorption.