Mitigation Of Alkaline Mine Drainage In A Natural Wetland System
Free (open access)
J. Kelly, P. Champagne & F. Michel
Many studies have focused on the generation and mitigation of acidic drainage generated when sulfide bearing material is exposed to the atmosphere and undergoes oxidation. Neutral or alkaline mine drainage can be produced from mining waste containing little or no sulfides, and such drainage can also contain elevated metal concentrations, potentially impacting receiving environments. The goal of this study was to characterize the biogeochemical interactions occurring throughout a natural wetland located in the Farr Creek drainage area in Cobalt Canada and to evaluate the ability of the system to effectively attenuate alkaline mine drainage. The biological characterization of the sediment samples demonstrated the presence of acid producing bacteria in consistent numbers with sulphate reducing bacteria and iron reducing bacteria. The data suggested that the acid produced by these active bacterial populations was immediately neutralized by the dissolution of carbonate minerals within the tailings, yielding a neutral to alkaline drainage. The distribution of metals including As, Co, Cu, and Zn throughout the sediments, pore water, and vegetation samples collected at various core locations the metal mass was primarily bound in the sediments or adsorbed onto organic matter or oxide fractions of the sediments. Phytoremediation processes involving Typha latifolia were shown to attenuate metals, particularly Cu and Zn. Adsorption onto organic matter and oxides was another attenuation pathway that significantly improved metal retention. Iron and sulfate reduction were also found to lead to the formation of metal sulfide precipitates, thereby immobilizing the metals. Keywords: wetland, alkaline mine drainage, heavy metals, sequential extraction, phytoremediation, sulphate reducing bacteria, iron reducing bacteria, acid producing bacteria, Typha latifolia.
wetland, alkaline mine drainage, heavy metals, sequential extraction, phytoremediation, sulphate reducing bacteria, iron reducing bacteria, acid producing bacteria, Typha latifolia.