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Bloom, N. S., Preus, E., Kilner, P. I., von der Geest, E., & Hensman, C. E. (2002). Very efficient removal of toxic metals from acid mine drainage water (Berkeley Pit, Montana) with a recycled alkaline industrial waste product Hardrock mining 2002; issues shaping the industry..
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Arango, I. (2002). Evaluation of the beneficial effects of the acidophilic alga Euglena mutabilis on acid mine drainage systems. Ph.D. thesis, Indiana State University,, Terre Haute.
Abstract: Euglena mutabilis is an acidophilic, photosynthetic protozoan that forms benthic mats in acid mine drainage (AMD) channels. At the Green Valley mine, western Indiana, E. mutabilis resides in AMD measuring <4.2 pH, with high concentrations of dissolved constituents (up to 22.67 g/l). One of the main factors influencing E. mutabilis distribution is water temperature. The microbe forms thick (>1 mm), extensive mats during spring and fall, when water temperature is between 13 and 28 degrees C. During winter and summer, when temperatures are outside this range, benthic communities have a very patchy distribution and are restricted to areas protected from extreme temperature changes. E. mutabilis also responds to rapid increases in pH, which are associated with rainfall events. During these events pH can increase above 4.0, causing precipitation of Fe and Al oxy-hydroxides that cover the mats. The microbe responds by moving through the precipitates, due to phototaxis, and reestablishing the community at the sediment-water interface within 12 hours. The biological activities of E. mutabilis may have a beneficial effect on AMD systems by removing iron from effluent via oxygenic photosynthesis, and/or by internal sequestration. Photosynthesis by E. mutabilis contributes elevated concentrations of dissolved oxygen (DO), up to 17.25 mg/l in the field and up to 11.83 mg/l in the laboratory, driving oxidation and precipitation of reduced metal species, especially Fe (II), which are dissolved in the effluent. In addition, preliminary electro-microscopic and staining analyses of the reddish intracellular granules in E. mutabilis indicate that the granules contain iron, suggesting that E. mutabilis sequesters iron from AMD. Inductive coupled plasma analysis of iron concentration in AMD with and without E. mutabilis also shows that E. mutabilis accelerates the rate of Fe removal from the media. Whether iron removal is accelerated by internal sequestration of iron and/or by precipitation via oxygenic photosynthesis has yet to be determined. These biological activities may play an important role in the natural remediation of AMD systems.
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Lin, C., Lu, W., & Wu, Y. (2005). Agricultural soils irrigated with acidic mine water: Acidity, heavy metals, and crop contamination. Australian Journal of Soil Research, 43(7), 819–826.
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.
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