SULFUR, IRON AND SOLID-PHASE TRANSFORMATIONS DURING THE BIOLOGICAL OXIDATION OF PYRITIC MINE SPOIL

Spoil material composed of pyrite, coal and rock was ground and inoculated with spoil microflora and monitored for pH, SO4(2-), reduced S compounds, total soluble Pe and Fe(II). A 7-day lag in production of both SO4(2-) and total soluble Fe was observed followed by a marked increase in concentration. Concentrations of SO4(2-), total soluble Fe and Fe(II) after 28 days were ca 81, 91, and 59 mmol kg-1 spoil, respectively. Reduced S anions including thiosulfate, trithionate and tetrathionate were detected in the spoil at all samplings during a 28-day incubation. Final trithionate concentrations were greatest (1.07 mmol kg-1 spoil). Scanning electron microscope observations of the pyrite revealed a gradual pitting and erosion of particle faces after prolonged incubation. Certain faces appeared to have been preferentially weathered.