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Boulder City, CO, United States

Thallium (Tl) may exceed regulatory limits in mining-influenced water (MIW) associated with processing cadmium, copper, gold, lead, and zinc ores. It is a toxic metal that is soluble over a wide pH range, resulting in both persistence in the environment and poor removal by conventional lime precipitation. This study evaluated the effect of potassium permanganate (KMnO4) at alkaline pH on Tl removal from MIW in batch experiments. The oxidation of Tl+ to Tl3+ by KMnO4 and subsequent Tl removal was explored at Tl concentrations of ≤1 mg/L in synthetic and actual MIW. In addition to Tl, the synthetic MIW contained ≈5 mg/L of Mn, while the actual MIW contained >10 mg/L of Al, Cu, Fe, Mn, and Zn and had a pH ≈ 2.5. Dissolved Tl <2 μg/L in synthetic MIW was achieved at a pH ≈ 9 (CaO addition) and ≥5 mg/L of KMnO4. In the actual MIW, dissolved Tl <2 μg/L was achieved at pH ≈ 9 and ≥12 mg/L of KMnO4. The Tl removal mechanism is complicated due to the presence of reduced Mn in the synthetic MIW and multiple metals in the actual MIW. However, effective Tl removal was achieved by adding KMnO4 to synthetic and actual MIW at alkaline pH. © 2015 Springer-Verlag Berlin Heidelberg Source


Stone J.J.,South Dakota School of Mines and Technology | Larson L.N.,South Dakota School of Mines and Technology | Kipp G.G.,Geomega
28th Annual Meeting of the American Society of Mining and Reclamation 2011 | Year: 2011

The extent of historical uranium mining impacts is well documented for the North Cave Hills region of Harding County, South Dakota. While previous studies indicate watershed sediment and surface water exhibit up to 90x established background concentrations for arsenic (As) and uranium (U), it was unclear whether or how localized changes in sediment redox behavior influence contaminant remobilization. Five pore-water equilibration samplers (peepers) were spatially and temporally deployed within the study area to evaluate seasonal solid-liquid equilibria as a function of sediment depth. At a sampling site 2 km downstream of the mine site within a wetlands-dominated deposition zone, seasonal variations of pore-water geochemistry were observed. Summer conditions promoted strongly reducing conditions, resulting in the remobilization of sediment-bound As(III). Fall conditions promoted oxidizing conditions within the sediments, resulting in decreased As (5x) and increased U (10x) concentrations within the sediment pore-waters. Peak pore-water U concentrations (781 μg/L) were 3.5x greater than observed within the surface water (226 μg/L) immediately above the sediments. Pore-water As(V) concentrations peaked directly below the sediment-water interface, suggesting As(V) was scavenged and accumulated by strong interactions with surficial iron (hydr)oxides. The study results suggest that localized redox conditions, especially those dominated by (bio)geochemically-influenced iron and sulfur reducing processes, may influence seasonal As and U behavior within these mining impacted alluvium sediments. Source


Schmidt S.K.,University of Colorado at Boulder | Cleveland C.C.,University of Montana | Nemergut D.R.,University of Colorado at Boulder | Reed S.C.,U.S. Geological Survey | And 2 more authors.
Geoderma | Year: 2011

Estimating phosphorus (P) availability is difficult-particularly in infertile soils such as those exposed after glacial recession-because standard P extraction methods may not mimic biological acquisition pathways. We developed an approach, based on microbial CO2 production kinetics and conserved carbon:phosphorus (C:P) ratios, to estimate the amount of P available for microbial growth in soils and compared this method to traditional, operationally-defined indicators of P availability. Along a primary succession gradient in the High Andes of Perú, P additions stimulated the growth-related (logistic) kinetics of glutamate mineralization in soils that had been deglaciated from 0 to 5years suggesting that microbial growth was limited by soil P availability. We then used a logistic model to estimate the amount of C incorporated into biomass in P-limited soils, allowing us to estimate total microbial P uptake based on a conservative C:P ratio of 28:1 (mass:mass). Using this approach, we estimated that there was <1μg/g of microbial-available P in recently de-glaciated soils in both years of this study. These estimates fell well below estimates of available soil P obtained using traditional extraction procedures. Our results give both theoretical and practical insights into the kinetics of C and P utilization in young soils, as well as show changes in microbial P availability during early stages of soil development. © 2011 Elsevier B.V. Source


Larson L.N.,South Dakota School of Mines and Technology | Kipp G.G.,Geomega | Mott H.V.,South Dakota School of Mines and Technology | Stone J.J.,South Dakota School of Mines and Technology
Applied Geochemistry | Year: 2012

The extent of historical U mining impacts is well documented for the North Cave Hills region of Harding County, South Dakota, USA. While previous studies reported watershed sediment and surface water As and U concentrations up to 90× established background concentrations, it was unclear whether or how localized changes in sediment redox behavior may influence contaminant remobilization. Five pore-water equilibration samplers (peepers) were spatially and temporally deployed within the study area to evaluate seasonal solid-liquid As and U distributions as a function of sediment depth. Pore-water and solid phase As and U concentrations, Fe speciation, Eh and pH were measured to ascertain specific geochemical conditions responsible for As and U remobilization and transport behavior. At a mine overburden sedimentation pond adjacent to the mine sites, high total aqueous As and U concentrations (4920 and 674μg/L, respectively) were found within surface water during summer sampling; however pond dredging prior to autumn sampling resulted in significantly lower aqueous As and U concentrations (579 and 108μg/L, respectively); however, both As and U still exceeded regional background concentrations (20 and 18μg/L, respectively). At a wetlands-dominated deposition zone approximately 2km downstream of the sedimentation pond, pore-water geochemical conditions varied seasonally. Summer conditions promoted reducing conditions in pore water, resulting in active release of As(III) to the water column. Autumn conditions promoted oxidizing conditions, decreasing pore-water As (As pw) 5× and increasing U pw 10×. Peak U pore-water concentrations (781μg/L) were 3.5× greater than determined for the surface water (226μg/L), and approximately 40× background concentrations. At the Bowman-Haley reservoir backwaters 45km downstream from the mine sites, As and U pore-water concentrations increased significantly between the summer and autumn deployments, attributed to increased Fe reduction processes. Geochemical modeling suggests solid-phase Fe reduction promotes the liberation of pore-water As and U via suppressing the formation of thioarsenite. Intermittent hydrological processes facilitate As and U transport and deposition throughout the watershed, while biogeochemical-influenced redox changes cycle As and U between pore and surface water within localized environments. © 2012 Elsevier Ltd. Source


Thallium (Tl) may exceed regulatory limits in mining-influenced water (MIW) associated with processing cadmium, copper, gold, lead, and zinc ores. It is a toxic metal that is soluble over a wide pH range, resulting in both persistence in the environment and poor removal by conventional lime precipitation. This study evaluated the effect of potassium permanganate (KMnO4) at alkaline pH on Tl removal from MIW in batch experiments. The oxidation of Tl+ to Tl3+ by KMnO4 and subsequent Tl removal was explored at Tl concentrations of ≤1 mg/L in synthetic and actual MIW. In addition to Tl, the synthetic MIW contained ≈5 mg/L of Mn, while the actual MIW contained >10 mg/L of Al, Cu, Fe, Mn, and Zn and had a pH ≈ 2.5. Dissolved Tl <2 μg/L in synthetic MIW was achieved at a pH ≈ 9 (CaO addition) and ≥5 mg/L of KMnO4. In the actual MIW, dissolved Tl <2 μg/L was achieved at pH ≈ 9 and ≥12 mg/L of KMnO4. The Tl removal mechanism is complicated due to the presence of reduced Mn in the synthetic MIW and multiple metals in the actual MIW. However, effective Tl removal was achieved by adding KMnO4 to synthetic and actual MIW at alkaline pH. © 2015, Springer-Verlag Berlin Heidelberg. Source

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