Abstract: Agricultural soils irrigated with acidic mine water from the Guangdong Dabaoshan Mine, China, were investigated. The pH of the soils could be as low as 3.9. However, most of the mineral acids introduced into the soils by irrigation were transformed to insoluble forms through acid buffering processes and thus temporarily stored in the soils. Different heavy metals exhibited different fraction distribution patterns, with Zn and Cu being mainly associated with organic matter and Pb being primarily bound to oxides (statistically significant at P = 0.05). Although the mean of exchangeable Cd was greatest among the Cd fractions, there was no statistically significant difference between the exchangeable Cd and the oxide-bound Cd (the 2nd greatest fraction) or between the exchangeable Cd and the carbonate-bound Cd (the 3rd greatest fraction). It was also found that there were generally good relationships between the concentrations of various Zn, Cu, Pb, and Cd fractions and pH, suggesting that a major proportion of each heavy metal in the soils was mainly derived from the acidic irrigation water. The results also show that the crops grown in these soils were highly contaminated by heavy metals, particularly Cd. The concentration of Cd in the edible portions of most crops was far in excess of the limits set in China National Standards for Vegetables and Fruits and this can be attributable to the extremely high transfer rate of Cd from the soils to the crops under the cropping system adopted in the study area. < copyright > CSIRO 2005.

Abstract: A field demonstration of the Green World Science® patented process technology was performed to address acid mine drainage (AMD) at an abandoned bituminous coal mine, the Tide Mine in Center Township, Indiana County, PA. ARCADIS owns an exclusive patent license of the Green World Science® process, which can be used in situ to transform an aerobic, AMD-producing mine pool to a biologically mediated, sulfate-reducing state. The Green World Science® process treats the entire mine pool to address the source of AMD in place. The project was conducted through a grant agreement between the Blacklick Creek Watershed Association, the Pennsylvania Department of Environmental Protection's Bureau of Abandoned Mine Reclamation, and ARCADIS. In conjunction with the characterization of mine pool hydraulics through injection of a bromide tracer, the in situ treatments implemented at Tide Mine include the initial addition of alkalinity to create an environment suitable for biological activity, injection of organic carbon into the mine pool to facilitate microbially mediated metals reduction and precipitation, and injection of carbon dioxide gas into the atmosphere above the mine pool to control the dominant source of oxygen that perpetuates the AMD process. Collectively, these treatments raised the pH from a baseline of approximately 2.5 to over 6 during the demonstration period. The mine pool subsequently maintains a pH above 5 through microbially produced (i.e., bicarbonate) alkalinity. Ferric iron has been reduced to non-detect concentrations within the anaerobic mine pool, and aluminum concentrations have decreased by approximately 30%, with additional metals removal expected as the system becomes controlled by ferrous sulfide precipitation. The injection of carbon dioxide gas into the mine workings decreased oxygen concentrations above the mine pool from over 20% (ambient air conditions) to less than 5% over approximately three months, thus mitigating the source of AMD within the mine.

Abstract: Mining is implicated as a significant contributor to water pollution, the prime reason being, that pyrites oxidize to sulphuric acid when exposed to air and water. Mine effluents, often containing sulphate, acidity and metals, should be treated to render it suitable for re-use in the mining industry, for irrigation of crops or for discharge in water bodies. This study describes the removal of all three mentioned pollutants in mine effluents, from different origins, containing different concentrations of various metals. The objectives were achieved, applying the biological sulphate removal technology, using ethanol as the carbon and energy source. It was shown that diluting the mine effluent with the effluent from the biological treatment, the pH increased due to the alkalinity in the treated water while the metals precipitated with the produced sulphide. When this treatment regime was changed and the mine water was fed undiluted, it was found that the metals stimulated the methanogenic bacteria (MB) as trace elements. This resulted in a high COD utilization of the MB, such that too little COD was available for the SRB. Metal removal in all three studies was observed and in most instances the metals were eliminated to the required disposal concentration.