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    The importance of sediment sulfate reduction to the sulfate budget of an impoundment receiving acid mine drainage
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    Abstract:
    Alkalinity generation by bacterial sulfate reduction (SR) has been shown to be an important neutralizing agent for acid mine drainage and acid precipitation in lakes and reservoirs. In order to quantify the importance of SR in an acidified system, a sulfate influx‐efflux budget was constructed for Lake Anna, an impoundment in central Virginia that receives acid mine drainage. For the 1983 and 1984 water years, 48% (namely, 8.0 × 10 5 kg) of the sulfate entering the impoundment was removed from the water column within the first 2 km of the arm of the lake receiving the pollution. SR rates measured using 35 S‐labeled sulfate were extrapolated across the surface area of this arm of the lake; this calculated amount of sulfate removed was equal to 200% of the sulfate removed from the lake as calculated in the budget. The calculated alkalinity generated by this sulfate removal was more than twice that necessary to account for the observed p H increase in the impoundment. The magnitude of the sulfate removal and alkalinity generation demonstrates the quantitative importance of SR as an ecosystem level buffering mechanism.
    Keywords:
    Alkalinity
    Acid Mine Drainage
    Acid rain
    Variation of alkalinity and its relationship with the pH, volatile fatty acid (VFA) and COD along with the different compartments of the ABR were investigated. The experimental results showed that there was a close relationship between variation of alkalinity and VFA concentration along with the ABR compartments. The lowest point of alkalinity and pH value occurred where VFA concentration reached maximum. The effect of alkalinity on the operational performance was through changing pH value. The variation trend of alkalinity and pH along with different compartments was decreased firstly and then increased. The alkalinity should be controlled to guarantee the lowest pH no less than 6.0. The lowest alkalinity should be no less than 800 mg/L when the loading rate (COD) was about 3.7 kg/(m3 x d).
    Alkalinity
    Citations (1)
    Acid mine drainage (AMD) has properties of extreme acidification, quantities of sulfate and elevated levels of soluble heavy metals. It was a widespread environmental problem that caused adverse effects to the qualities of ground water and surface water. In the past decades, most of investigations were focused on the heavy metals as their toxicities for human and animals. As another main constitution of AMD, sulfate ion is nontoxic, yet high concentration of sulfate ion can cause many problems such as soil acidification, metal corrosion and health problems. More attention should be paid on the sulfate ion when people focus on the AMD. In the paper, sulfate removal mechanisms include adsorption, precipitation, co-precipitation and biological reduction were analyzed and summarized. Meanwhile, the remediation technologies, especially the applications of them in China were also presented and discussed.
    Acid Mine Drainage
    Acid rain
    Abstract Acid Mine Drainage (AMD) is one of the persistent water pollution problems in many coal mines of U.S.A. and Canada. Only few mines in India face this problem. The treatment of acid mine water has become a statutory requirement in almost all mines of the world. Metal removal and alkalinity generation is essential feature of any AMD treatment system but sulphate removal from acid mine drainage is still given the secondary importance. In the present study, four AMDs were treated in laboratory Successive Alkalinity Producing System (SAPS) for five different hydraulic retention times (HRT). The total iron removal and corresponding sulphate removal along with net alkalinity generation were studied during AMD treatment process by SAPS. A complete removal of total iron and sulphate removal of over 59% have been achieved. The study revealed that the total iron removal and sulphate removal increases with increase in HRT and its removal exhibited linear relationship. A substantial increase in alkalinity was also found after SAPS treatment. The findings of the study can be utilized in design of SAPS for removal of iron and sulphate during treatment of AMD in mining areas.
    Alkalinity
    Acid Mine Drainage
    Citations (2)
    Pore fluids from Clear Lake sediments collected near the abandoned Sulphur Bank Mercury Mine have low pH (locally <4) and elevated sulfate (> or =197 mmol/L), aluminum (> or =52 mmol/L), and iron (> or =28 mmol/L) contents derived from oxidation of sulfide minerals at the mine site. Acid mine drainage (AMD) is entering Clear Lake by advective subsurface flow nearest the mine and by diffusion at greater distances. Oxygen and hydrogen isotope ratios, combined with pore fluid compositions, constrain the sources and pathways of contaminated fluids. Sediment cores taken nearest the mine have the highest concentrations of dissolved sulfate, aluminum, and iron, which are contributed by direct subsurface flow of AMD from sulfide-bearing waste rock. Sediment cores as far as 100 m west of the Clear Lake shoreline show the presence of AMD that originated in the acidic lake that occupies the abandoned Herman Pit at the mine site. High sulfate content in the AMD has the potential to promote the activity of sulfate-reducing bacteria in the organic-rich lake sediments, which leads to methylation of Hg+2, making it both more toxic and bioavailable. Quantitative depletion of pore water sulfate at depth and sulfur isotope values of diagenetic pyrite near 0 per thousand indicate that sulfate availability limits the extent of sulfate reduction in the lake sediments away from the mine. Profiles of pore water sulfate in the sediments near the mine show that excess sulfate is available to support the activity of sulfate-reducing bacteria near the mine site. Enriched isotope values of dissolved sulfate (as high as 17.1 per thousand) and highly depleted isotope values for diagenetic pyrite (as low as -22.6 per thousand) indicate active bacterial sulfate reduction in the AMD-contaminated sediments. Sulfate- and iron-rich acid mine drainage entering Clear Lake by shallow subsurface flow likely needs to be controlled in order to lower the environmental impacts of Hg in the Clear Lake ecosystem.
    Acid Mine Drainage
    Sulfate-Reducing Bacteria
    Sulfide Minerals
    Citations (16)