A Study of a Hypersaline,Heliothermic Lake that Formed in an Anthropogenic-Karst Sinkhole

In Solotvino, in southwestern Ukraine (Transcarpathia), there is a large group of anthropogenic water reservoirs. Most of these developed in sinkholes formed by the flooding of salt mines and the activation of anthropogenic and karst processes. One reservoir, Solotvino No. 7, was the subject of detailed limnological (hydrographic and hydrochemical) studies. The reservoir has an area of 8493 m², a maximum depth of 20.5 m, and holds Cl^?–Na⁺ brines. The water in the near-surface layer is hyposaline (3–20 g/L), but periodically becomes mesosaline (20–50 g/L). Hypersaline waters with mineralization?>?250 g/L are found below 3 m. The reservoir has three persistent distinct mixolimnion layers that clearly indicate their meromictic type: the surface layer, a chemocline (where the water chemistry changes), and a lower monimolimnion layer. The thermal properties of the reservoir deserve special attention. The water is heated during all seasons at the boundary between the chemocline and monimolimnion; the water temperature is 32 °C in winter and 54 °C in summer, despite the lack of volcanism. The water is heated by a physical phenomenon in the layer where the water density increases, which is a heliothermal process. Also noteworthy is that throughout the year, the oxygen profiles are positive and heterograde, with the water being up to 380% oxygen saturated.

     

Physico-chemical gradients and meromictic stratification in Cueva de la Mora and other acidic pit lakes of the Iberian Pyrite Belt

A marked vertical trend of increasing temperature and dissolved metal concentrations is observed in the monimolimnia of some meromictic pit lakes of the Iberian Pyrite Belt (IPB) in SW Spain. Temperature differences between the chemocline and the pit lake bottom can be as high as 15°C (e.g. Herrerías), and the respective concentration of some metals (e.g. Fe) and metalloids (e.g. As) can increase by several orders of magnitude (e.g. Cueva de la Mora). The redox conditions also change drastically from the upper and oxygenated mixolimnion (strongly oxidizing) to the lower and anoxic monimolimnion (moderately reducing). Processes such as the inflow of metal–sulphate laden ground water from flooded shafts and galleries, and other factors such as the pit geometry or the relative depth of the lakes, must be considered to account for the observed stratification pattern. The vertical profiles of physico-chemical parameters and water chemistry obtained in Cueva de la Mora and other meromictic pit lakes of the IPB are also compatible with a reactive bottom in which several geochemical and microbial reactions (including reductive dissolution of Fe³⁺ minerals, bacterial reduction of Fe³⁺ and SO₄ ²⁻ in pore waters within the sediments, and decomposition of organic matter) could be taking place.     

Defining the Extent of Mine-Influenced Groundwater in a Mineralized and Agricultural Area Using Multiple Lines of Evidence

Mine-influenced groundwater (MIW) at a former copper mine site has affected an alluvial aquifer that also contains groundwater with solutes characteristic of natural mineralization and agricultural activities. Many of the solutes are common to at least two of three potential sources, and some solutes (e.g., sulfate and uranium) are common to all three. This precludes the conventional use of one, or several, characteristic solutes to identify the extent of MIW. So, we used five independent lines of evidence (LOE) to define the extent of MIW in the alluvial aquifer. The five LOE are multivariate statistical analysis of an extensive groundwater analyte suite, groundwater sulfur isotope (δ³⁴S_SO4) data, probabilistic calculations of groundwater velocity and flow distance, isotopic (³H/³He) estimates of groundwater age, and extent of nitrate in groundwater originating from agricultural activities.

     

Distribution of Organic Carbon in the Berkeley Pit Lake, Butte, Montana

Abstract.  The concentration of dissolved organic carbon (DOC) in the Berkeley pit lake water ranges from 2 to 4 mg/L, and is comparable to that of its inflow waters. On the dates sampled, the DOC concentrations decreased towards the surface of the lake, in a manner similar to the concentration of dissolved Fe. This may reflect adsorption of DOC onto newly formed ferric precipitates in the epilimnion of the lake. The total organic carbon (TOC) content of the lake sediment is 0.20 to 0.33%, and is on the low end of TOC in natural aquatic sediments. In contrast, the DOC concentrations of sediment pore waters are unusually high, ranging from 50 to 380 mg/L, and are much higher than DOC values of pore waters from typical marine or lacustrine sediments. The high DOC concentrations are explained by release of adsorbed organic carbon from ferric precipitates as they age and recrystallize, coupled with the relative scarcity of heterotrophic bacteria in the acidic and heavy metal-rich waters that would otherwise consume DOC through reduction of sulfate.     

Environmental Geochemistry and a Quality Assessment of Mine Water of the West Bokaro Coalfield,India

Mine water from the West Bokaro coalfield was qualitatively assessed with respect to domestic and irrigation criteria. Thirty water samples from different mines were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, major cations, anions, and dissolved silica. The pH of the samples ranged from 6.6 to 8.3 in the post-monsoon season and 6.7–8.4 in the pre-monsoon season, indicating its near-neutral to slightly alkaline nature. TDS ranged from 349 to 1029 mg L^?1 in the post-monsoon season and 499–1458 mg L^?1 in the pre-monsoon season. The spatial differences in TDS reflect the local lithology, surface activities, and hydrology. Ca–Mg–SO₄ and Ca–Mg–HCO₃ were the dominant hydrogeochemical facies; SO₄ ^2? and HCO₃ ^? were the dominant anions and Ca²⁺ and Mg²⁺ were the dominant cations during both seasons. High SO₄ ^2? concentrations are attributed to oxidative weathering of pyrite and gypsum dissolution. Computed supersaturation with respect to dolomite and calcite for most samples may result from the dissolution of gypsum after the water is saturated with respect to the carbonate minerals. Despite moderate to high TDS, total hardness, and SO₄ ^2? concentrations, most of the sampled mine water was of good to permissible quality for irrigation; however, locally higher salinity and Mg restrict its suitability for irrigation at some sites.     

Antimony Mobilisation and Attenuation During Ore Processing at Orogenic Gold Mines,Southern New Zealand

Mine waters at the Reefton orogenic gold mine (active from 2007 to 2016) in southern New Zealand contained dissolved arsenic (As) and antimony (Sb) up to 5 mg/L during production of a sulfide concentrate that included arsenopyrite (FeAsS) and stibnite (Sb₂S₃). Ferric oxyhydroxide adsorption extracted As down to?<?0.1 mg/L but dissolved Sb remained elevated due to adsorption competition with As. The Reefton sulfide concentrate was transported 700 km to the Macraes orogenic gold mine (active from 1990) for processing through a pressure oxidation autoclave at 225 °C. The Macraes ore has low Sb contents, so the temporary introduction of a Sb-rich component produced a short-term Sb signal in the autoclave system and tailings waters. Oxidation of stibnite occurred rapidly in the autoclave, in parallel with the As in the arsenopyrite, producing ferric antimonate (tentatively identified as As-bearing tripuhyite) and ferric arsenate (FeAsO₄). Dissolved Sb in the Macraes tailings waters remained?<?0.1 mg/L throughout the period of Reefton concentrate addition. The formation of tripuhyite in the high-temperature autoclave stabilised Sb in the Macraes tailings, so that dissolved Sb?<?As, in contrast to the low-temperature processes at Reefton where dissolved Sb?>?As.

     

Bioleaching of phosphorus from rock phosphate containing pyrites by Acidithiobacillus ferrooxidans

Pyrites can be oxidized by the bacterium Acidithiobacillus ferrooxidans (At. f.), producing H₂SO₄ and FeSO₄. Rock phosphate is dissolved by H₂SO₄, forming soluble phosphorus. Fe²⁺ in FeSO₄ is oxidized to Fe³⁺, producing energy to sustain the growth of At. f. The effects of four factors (rock phosphate dosage, pyrite dosage, culture temperature and time) on the fraction of phosphorous leached were investigated. It is suggested that the optimal conditions are as follows: rock phosphate dosage 1 g/L, pyrite dosage 30 g/L, culture temperature 30 °C, culture time 84 h. The fraction of phosphorous leached is up to 11.8%.     

The Oxidative Precipitation of Thallium at Alkaline pH for Treatment of Mining Influenced Water

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.     

Passive aerobic treatment of net-alkaline,iron-laden drainage from a flooded underground anthracite mine,Pennsylvania, USA

This report evaluates the results of a continuous 4.5-day laboratory aeration experiment and the first year of passive, aerobic treatment of abandoned mine drainage (AMD) from a typical flooded underground anthracite mine in eastern Pennsylvania, USA. During 1991–2006, the AMD source, locally known as the Otto Discharge, had flows from 20 to 270 L/s (median 92 L/s) and water quality that was consistently suboxic (median 0.9 mg/L O₂) and circumneutral (pH ≈ 6.0; net alkalinity >10) with moderate concentrations of dissolved iron and manganese and low concentrations of dissolved aluminum (medians of 11, 2.2, and <0.2 mg/L, respectively). In 2001, the laboratory aeration experiment demonstrated rapid oxidation of ferrous iron (Fe²⁺) without supplemental alkalinity; the initial Fe²⁺ concentration of 16.4 mg/L decreased to less than 0.5 mg/L within 24 h; pH values increased rapidly from 5.8 to 7.2, ultimately attaining a steady-state value of 7.5. The increased pH coincided with a rapid decrease in the partial pressure of carbon dioxide (PCO₂) from an initial value of 10^−1.1 atm to a steady-state value of 10^−3.1 atm. From these results, a staged aerobic treatment system was conceptualized consisting of a 2 m deep pond with innovative aeration and recirculation to promote rapid oxidation of Fe²⁺, two 0.3 m deep wetlands to facilitate iron solids removal, and a supplemental oxic limestone drain for dissolved manganese and trace-metal removal. The system was constructed, but without the aeration mechanism, and began operation in June 2005. During the first 12 months of operation, estimated detention times in the treatment system ranged from 9 to 38 h. However, in contrast with 80–100% removal of Fe²⁺ over similar elapsed times during the laboratory aeration experiment, the treatment system typically removed less than 35% of the influent Fe²⁺. Although concentrations of dissolved CO₂ decreased progressively within the treatment system, the PCO₂ values for treated effluent remained elevated (10^−2.4 to 10^−1.7 atm). The elevated PCO₂ maintained the pH within the system at values less than 7 and hence slowed the rate of Fe²⁺ oxidation compared to the aeration experiment. Kinetic models of Fe²⁺ oxidation that consider effects of pH and dissolved O₂ were incorporated in the geochemical computer program PHREEQC to evaluate the effects of detention time, pH, and other variables on Fe²⁺ oxidation and removal rates. These models and the laboratory aeration experiment indicate that performance of this and other aerobic wetlands for treatment of net-alkaline AMD could be improved by aggressive, continuous aeration in the initial stage to decrease PCO₂, increase pH, and accelerate Fe²⁺ oxidation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Iron Removal by a Passive System Treating Alkaline Coal Mine Drainage

The Marchand passive treatment system was constructed in 2006 for a 6,000 L/min discharge from an abandoned underground bituminous coal mine located in western Pennsylvania, USA. The system consists of six serially connected ponds followed by a large constructed wetland. Treatment performance was monitored between December 2006 and 2007. The system inflow was alkaline with pH 6.2, 337 mg/L CaCO₃ alkalinity, 74 mg/L Fe, 1 mg/L Mn, and <1 mg/L Al. The final discharge averaged pH 7.5, 214 mg/L CaCO₃ alkalinity, and 0.8 mg/L Fe. The settling ponds removed 84% of the Fe at an average rate of 26 g Fe m⁻² day⁻¹. The constructed wetland removed residual Fe at a rate of 4 g Fe m⁻² day⁻¹. Analyses of dissolved and particulate Fe fractions indicated that Fe removal was limited in the ponds by the rate of iron oxidation and in the wetland by the rate of particulate iron settling. The treatment effectiveness of the system did not substantially degrade during cold weather or at high flows. The system cost $1.3 million (2006) or $207 (US) per L/min of average flow. Annual maintenance and sampling costs are projected at $10,000 per year. The 25-year present value cost estimate (4% discount rate) is $1.45 million or $0.018 per 1,000 L of treated flow.     

Synchrotron X-ray photoelectron spectroscopic study of the chalcopyrite leached by moderate thermophiles and mesophiles

SXPS (Synchrotron X-ray Photoelectron Spectroscopy) and NEXAFS (Near Edge X-ray Absorption Fine Structures) have been applied to study the surface chemical species of chalcopyrite leached by a moderate thermophilic consortia, Leptospirillum ferrooxidans and a mesophilic mixed culture of L. ferrooxidans, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A sulfur-rich layer dominated by S_n²⁻ developed with time, which was found to control the rate of bioleaching. Fe L_2,3-edge NEXAFS and Fe 2p spectra indicate the formation of jarosite during bioleaching. Thermophiles significantly enhanced the leaching efficiency, in which 1.34 g/L copper was dissolved in 25 days, while less than 0.3 g/L copper was released in 30 °C bioleaching. This was mostly caused by the increased abiotic reaction rate. The solution copper concentration in presence of L. ferrooxidans was higher than that with mesophilic mixed culture, which suggests the synergistic effect of mixed microorganisms did not play a comparably important role as temperature under the conditions used in this study. Explicit evidence of elemental sulfur was only found in samples leached by L. ferrooxidans by Raman spectroscopy. However, the formation of elemental sulfur does not significantly hinder the leach rate.     

Pyrite Weathering in Reclaimed Shale Overburden at an Oil Sands Mine near Fort McMurray,Canada

Saline-sodic shale overburden associated with oil sand mining is a potential source of salt release to surface water and groundwater and can lead to salinization and/or sodification of reclamation covers. Weathering of shale overburden due to oxidation of sulphide minerals within the shale leads to sulphate (SO₄ ^2?) production and increased salinity. The controls on the rates of weathering of a shale overburden dump in the oil sands region of northern Alberta were determined from soil chemistry sampling and in situ monitoring of pore gases (O₂, CO₂, CH₄) in three shallow profiles (1.9–4.45 m deep) and one deep (25 m deep) profile under reclamation covers of varying thickness. Oxidation, defined by the depth over which O₂ concentrations were depleted, reached depths of approximately 1.1 m under the reclamation soil covers over a 6 year period after dump placement. Calculations of SO₄ ^2? production rates and weathering depths were consistent with numerical simulations of the diffusion and subsequent consumption of atmospheric O₂ in the overburden. The rate of SO₄ ^2? production during the 6 year weathering period estimated from direct measurements of solids chemistry ranged from 0.70 to 8.3 g m^?2 day^?1. The rates calculated from the oxygen diffusion models were within that same range, between 1.6 and 4.1 g m^?2 day^?1.     

The Use of Static and Humidity Cell Tests to Assess the Effectiveness of Coal Waste Desulfurization on Acid Rock Drainage Risk

The environmental benefits of waste desulfurization were evaluated in the Santa Catarina coal field, Brazil. Coal waste from a beneficiation plant was separated into three density fractions, using a two stage process. Characterization of these fractions indicated that the low (D?<?2.2 g/cm³) and high (D?>?2.7 g/cm³) density fractions were potentially suitable for energy and sulfuric acid production, respectively. The waste fraction of intermediate density (2.2?<?D?<?2.7 g/cm³) represented 69% of the total mass studied and had a relatively low sulfide content, and it was postulated that it may be suitable for land disposal with minimum risk to the surrounding environment. This hypothesis was tested using laboratory-scale static and kinetic tests, which indicated that although the fraction remained net acid generating, the rate and net amount of metals, salts, and acidity that leached was considerably less than that of the discards before separation. It was concluded that this approach could reduce the amount of waste generated, as well as the associated pollution risk.     

Geochemistry and Isotopic Composition of H2S-rich Water in Flooded Underground Mine Workings,Butte, Montana,USA

Abstract.   Groundwater being pumped from the flooded West Camp mine workings of Butte, Montana, is elevated in hydrogen sulfide (H₂S), has a circum-neutral pH, and has high arsenic but otherwise low metal concentrations. The daily flux of H₂S and As pumped from the extraction well are each estimated at roughly 0.1 kg. Isotopic analysis of coexisting aqueous sulfide and sulfate confirms that the H₂S was produced by bacterial sulfate reduction. the mine waters are close to equilibrium saturation with amorphous FeS, amorphous ZnS, siderite, rhodochrosite, calcite, and goethite, but are undersaturated with orpiment (As₂S₃). The higher solubility of orpiment relative to other mental sulfides allows concentrations of dissolved arsenic (~ 100 g/L) that are well above human health standards. The West Camp waters differ markedly from the acidic and heavy metal-rich mine waters of the nearby Berkeley pit-lake. These differences are partly attributed to geology, and partly to mining history.     

高密度泥浆法处理某硫铁矿酸性废水工艺优化研究

采用高密度泥浆法处理某硫铁矿酸性废水,进行了工艺参数优化研究与经济性分析。实验得到最优工艺条件为：系统水力停留时间30 min,气水比5:1,pH 9.0-9.2,石灰投加量0.83 kg/m₃^,PAM投加量15 g/m₃^,回调pH的硫酸(浓度98%)用量为0.0167L/m₃^{。结果表明},最优工艺条件下出水水质可以稳定达到《铜、镍、钴工业污染物排放标准》(GB25467—2010)表2、《铁矿采选行业废水污染物排放标准》(GB28661-2012)表2和《污水综合排放标准》(GB8978-1996)一级标准中规定的污染物限值要求。HDS工艺的运行成本约为1.57元/m₃^废水,具有较好的经济性,实验结果可作为废水处理站提升改造工程的设计依据。     

Entrainment of particles with density between 1.01 and 1.10 g/cm3 in a monobubble hallimond flotation tube

It was established in this study that the entrainment of low density particles in the monobubble Hallimond flotation cell with densities between 1.01 and 1.10 g/cm³ obeys the equation: L_L = d₅₀{(ϱ_p−ϱ_w)/ϱ_w}^0.75 = 0.0225±0.0025 (cm) where d₅₀ is the size of particles (in cm) for which the recovery due to entrainment is 50%, ϱ_p is the density of particle (in g/cm³), ϱ_w stands for the density of water while L_L is a constant (in cm). Equation (a) is identical with the equation previously found for particles with densities between 1.10 and 2.00 g/cm³ and obeys Allen's (turbulent-near laminar) mode of freely settling particles in liquid media. Equation (a) is different from the equation for particles with densities greater than 2.0 g/cm³, for which the mechanical carryover in the Hallimond tube is governed by the Newton-type equation for particles settling turbulently: L_H = d₅₀(ϱ_p−ϱ_w/ϱ_w = 0.023±0.002 (cm) because the power factor for the (ϱ_p−ϱ_w)/ϱ_w term is 1 not 0.75.     

Influence of Past Mining on the Quality of Surface Waters at Funtana Raminosa (Sardinia)

Cu–Pb deposits at Funtana Raminosa in Central Sardinia were intensively exploited, mostly underground, from 1917 until 1983. Flotation tailings were dumped near the mine plant. A hydrogeochemical survey carried out in 2004 showed that mine drainage collected from several galleries was circumneutral, due to the availability of carbonate minerals that buffer the acidity produced by the oxidation of Fe-bearing sulphides. The mine waters contained higher concentrations of dissolved SO₄, F, Zn, Cd, Pb, Mn, and Mo than was observed in uncontaminated spring and stream waters in the area. Drainage from the oldest flotation tailings showed much lower concentrations of Zn, Cd, and Pb than those generally observed in mine waters. In contrast, drainage from the recent flotation tailings had the highest levels of dissolved SO₄, Zn, and Cd (1,600, 30, and 0.8 mg/L, respectively) when sampled in the dry season; these were two orders of magnitude lower in the rainy season under high flow condition. Pb was ≈ 5 μg/L under different flow conditions. Water in the Rio Saraxinus, a stream that drains the entire mining area, had a relatively low level of contamination (170 μg/L Zn, 7 μg/L Cd, and 0.9 μg/L Pb).     

基于TOUGHREACT模拟分析黄铁矿对酸法地浸采铀的影响

酸法地浸采铀过程中,铀矿的伴生矿黄铁矿作为非目标矿物会消耗氧化剂和酸。为探明酸法浸铀过程中因黄铁矿溶解产生的变化规律,本文以巴彦乌拉铀矿采铀过程为例,采用六注二抽的“网格式”井型构建二维酸法地浸采铀模型进行模拟研究,在抽注平衡的条件下,模型中只考虑黄铁矿(FeS₂),沥青铀矿(UO₂),与石英(SiO₂)。结果表明：1)模拟结束后(1000 d),在抽注单元控制的地下水流场作用下,边界处注液井的黄铁矿溶解范围呈两极分化,最远处抵达抽液孔,为30 m,最近仅距注液井8.4 m,而中间处注液井的黄铁矿溶解范围最远达27.8 m,最近达8 m；2)地浸采铀中的关键因素Fe^₃₊在氧化还原次序中排名靠后,黄铁矿未完全溶解之时,在缺少Fe^₃₊的情况下,铀矿的溶解速率极低,直至黄铁矿完全溶解时,铀矿溶解速率才迅速增加,模拟结束后(1000 d),边界处注液井铀矿完全溶解范围为距注液井7.2 m-12.8 m,中间处注液井铀矿完全溶解范围为距注液井7 m-11 m,此时溶浸液中的六价铀(UO_2²⁺)迁移前端距离抽液孔仅8.4 m；3)铀矿的浸出经过溶解(液相)-沉淀(固相)-再溶解(液相)的多次旋回,根据铀矿的溶解-沉淀量将其划分为完全溶解区,有效溶解区和沉淀区,模拟结束后(1000 d),注液孔1完全溶解区范围为7.2m-12.8 m,此时沉淀区已形成一个锥形区域,范围为18.6 m-21.6 m,同样在抽注作用的影响下,在靠近抽液孔方向上,锥形沉淀区的尖端铀矿沉淀量最多；4)在抽注单元控制的地下水流场作用下,黄铁矿与铀矿的溶解区域,均出现靠近抽液孔方向的溶解范围大于远离抽液孔方向的溶解范围。     

硫酸盐还原菌处理矿山酸性废水的试验研究

采用上流厌氧反应器连续处理矿山酸性废水,研究了水力停留时间、进水pH值、进水负荷对硫酸根还原效果的影响。获得最佳工艺参数为水力停留时间8 d,COD/SO^2-₄=1.6,进水SO^2-₄浓度2.3 g/L和进水pH=6.0。在温度30 ℃,HRT=8 d、COD/SO^2-₄=1.6,进水SO^2-₄浓度2.3 g/L,进水pH=4.5和废水稀释倍数为3倍的条件下,采用上流厌氧反应器连续成功运行59 d,反应器运行24 d后,硫酸根平均去除率为75.35%,铜离子的去除率达99.98﹪, 铁离子的去除率为88.87%,出水达到工业排放标准。