Waste Piles Research Articles

Geochemistry of self-burning coal mining residues from El Bierzo Coalfield (NW Spain): Environmental implications

The geochemical composition of unburned and burned/burning coal waste piles from past mining activities in El Bierzo Coalfield (NW Spain) was determined for the comprehensive characterization of the coals waste materials, for the identification of the mode of occurrence of environmental sensitive trace elements, and for the identification of geochemical changes induced by the thermal effects resulting from the combustion process. The methodologies used for the geochemical characterization of the coal and coal waste material included proximate analysis, ultimate analysis, inductively coupled plasma mass spectrometry for the determination of the inorganic composition of major and trace elements, and scanning electron microscopy with energy dispersive X-ray spectrometry. Considering the potentially hazardous trace elements, the results demonstrated that the unburned material are enriched in Pb, Sb, and Th, comparatively with the background of black shales (BBS). Considering the enrichment/depletion behavior of the elements in burned vs. unburned material, it was observed that Fe, K, Na, S, and Ti are enriched in burned material, while Ca, Mg, and P are depleted. The trace elements Nb, Re, Ta, Te, and W are enriched in burned waste material while Cd, Cu, Mn, Zn, and REE are depleted. Higher contents of oxygen and total sulfur, and lower content of carbon were determined in the burned/burning materials. The enrichment/depletion behavior of the elements is attributed to the self-burning process and to the changes caused by thermal effects. The enrichment of some elements may result from the elements' concentration due to the volatilization of other elements and organic matter consumption during the combustion process. The depletion of some elements may be associated with their volatilization during combustion. However, other reasons for this behavior, such as the elements mode of occurrence, weathering and/or leaching, should be considered. The investigation about the mode of occurrence of the worldwide potentially hazardous trace elements in coal wastes reveals that As, Cd, Pb, Sb and U are preferentially organically associated. However, As and Cd also presents some affinity with mineral mater. The elements Be, Co, Cr, Mn, Ni, Se and Th exhibit a significant association with mineral matter.

Pollutant flows from a phosphogypsum disposal area to an estuarine environment: An insight from geochemical signatures

Phosphogypsum wastes from phosphate fertilizer industries are stockpiled in stacks with high contamination potential. An assessment of the environmental impact, including the use of geochemical tracers such as rare earth elements (REE) and Cl/Br ratios, was carried out in the phosphogypsum stack located at the Estuary of Huelva (SW Spain). Inside the pile, highly polluted acid pore-waters flows up to the edge of the stack, emerging as small fluvial courses, known as edge outflows, which discharge directly into the estuary. The disposal area is divided into four zones; two unrestored zones with surface ponds of industrial process water and two a priori already-restored zones. However, an extensive sampling of edge outflows conducted in the perimeter of the four zones demonstrates the high potential of contamination of the whole stack, including those zones that were supposedly restored. These solutions are characterized by a pH of 1.9 and concentrations of 6100mg/L for P, 1970mg/L for S, 600mg/L for F, 200mg/L for NH4+, 100mg/L for Fe, 10–30mg/L for Zn, As and U, and 1–10mg/L for Cr, Cu and Cd. Preliminary restoration actions and those planned for the future prioritize removal of ponded process water and cover of the phosphogypsum with artificial topsoil. These actions presuppose that the ponded process water percolates through the porous medium towards the edge up to reach the estuary. However, geochemical tracers rule out this connection and point to an estuarine origin for these leachates, suggesting a possible tidal-induced leaching of the waste pile in depth. These findings would explain the ineffectiveness of preliminary restoration measures and should be considered for the development of new action plans.

Field evidence of CO2 sequestration by mineral carbonation in ultramafic milling wastes, Thetford Mines, Canada

Two experimental small-scale cells have been constructed in the field to better understand passive mineral carbonation under natural atmospheric conditions in the ultramafic milling wastes of Thetford Mines (Québec, Canada). The magnesium-rich milling wastes mainly consist of poorly sorted grains and fibers of lizardite and chrysotile, with smaller amounts of antigorite, brucite and magnetite. These wastes could serve as significant and long-term CO2 sinks but the mechanisms and rates of mineral carbonation are not well understood. In this paper, the design of the experimental cells along with observations on gas composition, gas pressure, soil temperature, volumetric water content and mineral composition are presented with the objective to better understand the mineral carbonation processes under natural conditions and to propose a conceptual model for mineral carbonation at the field cell scale. Low CO2 concentrations (5–50ppm) measured in the experimental cells and the presence of hydromagnesite suggest that natural and passive mineral carbonation is a significant process occurring in the magnesium-rich wastes (4kg/m3/year of sequestrated CO2). In the proposed conceptual model, atmospheric CO2 (∼400ppm) dissolves in the hygroscopic water of the piles, where weathering of magnesium silicates forms magnesium carbonates. Water saturation in the cells is relatively stable over time and varies between 0.4 and 0.65, which is higher than optimal saturation values proposed in the literature, reducing CO2 transport in the unsaturated zone. Gas-phase CO2 concentrations along with gas flow rate measurements in the cells suggest that the reaction is most active close to the surface and that diffusion of CO2 is the dominant transport mechanism in the wastes. Although the carbonation reaction is exothermic, no evidence of thermal convection has been observed in the experimental cells. This conceptual model will serve to support a reactive transport model in order to quantify and optimize the amount of CO2 that can be captured in chrysotile milling waste piles.

Research of Gypsum-Containing Raw Materials for Obtaining of Dry Building Mixes

The article presents the results of overall acid fluoride raw material utilization for obtaining dry building mixes. It demonstrates that waste acid fluoride, stored for a substantial amount of time in waste piles is a crystallizing fuse for anhydrite binding materials providing improved strength performance and reduction of solidification time. Overall utilization of acid fluoride allows solving ecological problems and reduces the cost of anhydrite finishing materials due to absence of sulfate chemical additives.

Copper Speciation in Variably Toxic Sediments at the Ely Copper Mine, Vermont, United States.

At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160-1200 times) and sediments (15-79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80-95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu.

Перенос элементов в газоаэрозольной фазе из отвалов Комсомольского золотоизвлекательного завода (Кемеровская обл.)

Перенос элементов в газоаэрозольной фазе из отвалов Комсомольского золотоизвлекательного завода (Кемеровская обл.)

Exploring a Waste Dump Site Failure – Possible Causes and Prevention Measures

Construction wastes are normally stored in areas away from urban cities. If the pile of the dumped wastes becomes too high, there will be a stability concern in addition to environmental issues. As an example to address this concern and to avoid possible failure of a waste site, this paper explores the recent slide failure of a construction waste dump site near a city in southern China. Information is gathered from online sources, news reports and Google earth images. Based on the available information, the pre-failure profile of the waste site is re-constructed. The stability of the waste pile is analyzed with numerical modelling based on simplified models of various scenarios. The intention is to explore the most influential factors which may cause failure on a dump site and to provide suggestions for prevention of failure in similar conditions. The analysis identified slope angle and height of a waste pile and water condition onsite as the most influential factors. General prevention measures are recommended.

高潜水位煤矿区生态风险识别与评价

PDF HTML阅读 XML下载 导出引用 引用提醒 高潜水位煤矿区生态风险识别与评价 DOI: 10.5846/stxb201503050430 作者: 作者单位: 中国矿业大学北京,中国矿业大学北京土地复垦与生态重建研究所,中国矿业大学北京土地复垦与生态重建研究所,北京大学经济学院;北京大学经济学院,中国矿业大学北京土地复垦与生态重建研究所 作者简介: 通讯作者: 中图分类号: TD88 基金项目: 国家自然科学基金项目资助（41401609）；中国矿业大学煤炭资源与安全开采国家重点实验室开放基金项目（SKLCRSM13KFB07） Ecological risk identification and assessment for a coal mine with a high groundwater table Author: Affiliation: State Key Laboratory of Coal Resources and Safe Mining,China University of Mining Technology Beijing;China;Institute of Land Reclamation and Ecological Restoration,China University of Mining and Technology Beijing;China;School of economics,Peking university,;China,Institute of Land Reclamation and Ecological Restoration,China University of Mining and Technology Beijing,Institute of Land Reclamation and Ecological Restoration,China University of Mining and Technology Beijing,School of economics,Peking university,Institute of Land Reclamation and Ecological Restoration,China University of Mining and Technology Beijing Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:生态风险评价是生态环境保护与管理的重要研究内容，并广泛运用于流域与较大范围的区域尺度的研究。以区域生态风险评价理论为基础，结合高潜水位煤矿区生态环境以及煤炭开采对生态系统造成的危害的特点，通过分析风险源、风险受体、生态终点以及暴露-响应过程，对高潜水位煤矿区生态风险的识别与评价方法进行了研究，构建了典型高潜水位煤矿区的生态风险识别与评价概念模型与空间分析框架，分析了煤矿区生态风险识别的主要技术手段与方法，并构建了以缓冲为主要手段的综合生态风险评价方法。选择山东东滩煤矿作为研究对象，针对研究区内存在的采煤塌陷、洪涝、污染、景观及社会等生态风险类型，定量评价其空间差异，并提出相应的风险防范措施。案例分析结果表明，研究区综合生态风险重度、中度、一般、轻度分别占到研究区的4.70%，64.00%，24.09%，7.20%。生态风险较高的区域主要位于矿区中西部，为煤矸石山、裸露煤炭堆积与发电厂分布区域；中度风险是研究区主要的风险类型。从降低生态风险保障矿区生态安全角度，在未来矿区规划与生态治理过程中，提出了具体的应对措施，包括：（1）注重源头控制；（2）建立高生态风险区域阻隔带；（3）加强污染的监测与控制；（4）采用边开采边治理技术。建议加强生态风险高区域的阻隔，建立生态缓冲带，减缓对整个矿区的综合影响，构建东滩煤矿生态风险防范的空间结构。 Abstract:Ecological risk assessment is one of the most important subdivisions in eco-environmental protection and management, and it is widely used to evaluate ecological risks on both watershed and regional scales. In this study, we conducted identification and ecological assessment by analyzing risk sources, bearer, ecological endpoints, and the exposure-response process on the basis of regional ecological risk assessment coupled with the unique characteristics of mining ecosystems in high groundwater table areas. The identification and evaluation method for ecological risk was studied, and an ecological assessment conceptual model and spatial analysis framework for a coal mine with high ground water were proposed. Furthermore, a comprehensive ecological risk assessment method was proposed on the basis of the spatial buffering theory. The proposed model identifies and assesses mining-induced ecological risks. The Dongtan coal mine in Shandong Province was selected to test this model and framework. The major ecological risks in this mine include land subsidence, floods, water pollution, landscape, and social issues. The degrees of single and comprehensive ecological risk were evaluated. On the basis of the analysis, ecological risk was quantitatively analyzed and spatial strategies for ecological planning in the coal mine were broached. Severe, moderate, general, and mild comprehensive ecological risks were 4.7%, 64%, 24.09%, and 7.2%, respectively. The high ecological risk was located mid-west of the coal mine with sites for coal waste piles, exposed coal, and power plants. Despite the small area occupied, enough attention should be paid to high ecological-risk areas because of their high potential of air, water, and soil pollution. The moderate ecological risk was the dominant risk-type and was present in 64% of the whole region, where most of the mining subsidence is distributed. Mining subsidence triggers flood, farmland loss, and related social issues. The general and low ecological risks were located in the mining industry square area and coal mine edges (where coal pillars protect the ground infrastructure), and were kept at a distance from pollution sources. On the basis of quantitative and spatial ecological risk assessment, specific recommendations were proposed after considering reduced ecological risk and protection from an ecological security perspective for the mine. The countermeasures and suggestions include:(1) Source control. Coal waste piles, exposed coal, and power plants are the main causes of pollution and are considered as point-source pollution; therefore, we recommend that the coal company should focus on source control, improve the comprehensive utilization of coal waste, eliminate exposed coal, and implement monitoring of water and air emissions in power plants. (2) Establishment of barriers for high ecological-risk areas. High ecological-risk areas were established over a long period and cannot be eliminated immediately; therefore, establishment of ecological buffer zones and barriers for mitigating the effects of high ecological risks is strongly recommended. Specific measures include shelterbelt construction and utilization of geotextiles. (3) Improved monitoring and pollution control. Field sampling was not conducted in this study; the coal company should build a monitoring system to assess high pollution levels and spatial distribution of ecological risk areas and consider the dominant wind direction. (4) Concurrent mining and reclamation, filling materials in high groundwater and plain coal mines, and concurrent mining and reclamation technology are recommended to protect the topsoil and improve land reclamation efficiency. 参考文献 相似文献 引证文献

煤矸石场植被恢复初期生态绩效评价

PDF HTML阅读 XML下载 导出引用 引用提醒 煤矸石场植被恢复初期生态绩效评价 DOI: 10.5846/stxb201409111807 作者: 作者单位: 山西大学环境与资源学院,山西大学环境与资源学院,山西大学环境与资源学院,山西大学黄土高原研究所,山西大学生命科学学院,山西潞安矿业集团司马煤业有限公司 作者简介: 通讯作者: 中图分类号: Q948.1 基金项目: 煤矿塌陷及废弃地复垦的生态绩效研究项目(1103100301) Ecological performance assessment on early plant reclamation in coal gangue yard Author: Affiliation: College of Environmental and Resource,Shanxi University,College of Environmental and Resource,Shanxi University,College of Environmental and Resource,Shanxi University,Institute of Loess Plateau,Shanxi University,College of Life Science,Shanxi University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以山西潞安矿业集团司马煤业有限公司煤矸石场生态恢复5年内(2009-2013年)的植被-土壤系统为研究对象,在固定监测样地调查的基础上,以空间变化代替时间变化,对煤矸石场人工种植乔木层条件下,草本植物自然恢复初期的生态绩效进行了评价,结果表明:1)相较于1a恢复期,煤矸石场植被恢复初期植物群落基本特征、土壤物理性质、土壤化学性质及其综合生态绩效在5a恢复期时均达到了"优"级水平;2)在足够长的恢复期内,人工种植乔木层条件下,草本植物的自然恢复可以实现矿区的植被重建;3)基于AHP-FCE评价模型,以1a恢复期为基准,通过各恢复期生态指标与1a恢复期相比的恢复程度设定绩效等级,对煤矸石场植被恢复初期的生态绩效进行评价,避免了以往选取天然次生群落为恢复目标,但又不确定其是否为最佳恢复效果的盲目性,为生态绩效评价提供了新思路。 Abstract:This study monitored the five-year dynamics of the plant-soil system in the coal gangue yard at Sima Coal Mine of Lu'an Group from 2009 to 2013. The fixed plots were established to use spatial dynamics to represent temporal changes. The assessment was made on the communities characteristics, soil physical and chemical properties, and the comprehensive ecological performance of the plant communities at the early phase of reclamation after reforestation. The results were as follows:1) The evaluation criterion of ecological performance included five ranks:"Optimal", "Fine", "Middle", "Low", "Lower" at the early stage of restoration on coal waste pile. Referential to the first year, the five-year recovery achieved the "Optimal" rank according to the communities characteristics, soil physical and chemical properties, and the comprehensive ecological functions in the reclaimed coal gangue yard. Notwithstanding the ecological performance of natural secondary community also showing the "Optimal" rank in this study, natural secondary community was not the perfect object for reforestation. This result predicted that the ecological performance of reforestation in coal gangue yard might be better than natural secondary community with recovery age. 2) Given sufficient time, the reforestation and the spontaneous herbal recovery would achieve the goal of vegetation reconstruction in the mining area. 3) By employing the AHP-FCE model, using the first-year as benchmark, the performance criteria could be made for ranking the ecological performance in the early phases of reclamation. This was advantageous over the traditional method that taken natural secondary communities as the reclamation goal, whose optimism was usually questionable for high uncertainty. In this regard, this study attempted to provide an innovative way in the practice of ecological performance assessment. Moreover, this paper would play an actively model-driven role in advancing the scientific implementation, management, and evaluation of the ecological restoration in the coal gangue yard. 参考文献 相似文献 引证文献

Applying persistent scatterer interferometry for surface displacement mapping in the Azul open pit manganese mine (Amazon region) with TerraSAR-X StripMap data

The Azul mining complex, located in the Carajas Mineral Province, Amazon region, encompasses the most important manganese mine in Brazil. Vale S.A. company operates three simultaneous open pit excavations (mines 1, 2, and 3) in the area, which are conducted on rock alteration products of low geomechanical quality related to sandstones, siltstones, and a lateritic cover. In order to monitor ground deformation, 33 TerraSAR-X (TSX-1) StripMap images covering the period of March 2012–April 2013 were used in the investigation. An advanced differential interferometric synthetic aperture radar (A-DInSAR) approach based on persistent scatterer interferometry (PSI) using an interferometric point target analysis algorithm was applied, and the results showed that most of the area was considered stable during the time span of the synthetic aperture radar acquisitions. However, persistent scatterers (PS) with high deformation rates were mapped over a waste pile, probably related to settlements, and also along the north flank of mine 1, indicative of cut slope movements toward the center of the pit. A spatial relationship of geological structures with PS was observed for this sector of the mine, given by PS showing deformation rates concentrated along a structural corridor with faults, fractures, and folds related to the Carajas fault system. Though only ground-based radar measurements for wall benches of mine 1 were available for a short time period of the TSX-1 coverage, the PS movement patterns showed concordance with geotechnical field measurements. The investigation emphasized the important role that satellite-based A-DInSAR can play for deformation monitoring and risk assessment in this kind of mining area.

Petrography and mineralogy of self-burning coal wastes from anthracite mining in the El Bierzo Coalfield (NW Spain)

Coal fires burning around the world over many years have been responsible for the loss of natural resources and also for negative environmental and human-health impacts. Study of self-burning coal wastes based on organic petrology, mineralogy and geochemistry allows the evaluation of factors responsible for the combustion process, and can also be used to assess the changes that are taking place in thermally affected materials. The main goal of this study is to characterize the materials from the Arroyo Galladas, Arroyo Mourin and Fabero coal waste piles, which resulted from coal mining in the El Bierzo Coalfield (NW Spain). Samples of coal, and of unburned and burned or burning coal waste material, were studied by optical microscopy and X-ray powder diffraction (XRD). The results demonstrate that some of the organic matter has preserved its characteristics, but other organic material shows signs of thermal alteration such as cracks, devolatilization vacuoles, dark reaction rims, plasticized edges, and increased or decreased vitrinite reflectance. The resistance of the unaltered organic matter to thermal effects is attributed to the coalification process previously undergone by these coals. The mineralogical composition of the samples indicates that newly formed minerals are present in the burned or burning material, including mullite, cristobalite, cordierite, hematite, jarosite, sanidine, anorthite, sulfur, pyrite, rozenite, coquimbite, tschermigite, boussingaultite and amorphous material. The formation of these minerals is attributed to combustion at maximum temperatures of at least 1100°C in the Fabero coal waste pile and lower temperatures in the Arroyo Galladas coal waste pile, and to interaction of gases released by combustion with the solid particles, the waters and the atmosphere in and around the waste piles.

Detection of mine slope motions in Brazil as revealed by satellite radar interferograms

Differential synthetic aperture radar interferometry (DInSAR) is a space-geodetic technique which allows minute surface displacements over vast areas to be detected with centimetric accuracy. Because of these unique characteristics, the DInSAR approach has great advantages over classical geodetic monitoring systems that allow the anticipation of high-risk situations. In the past few decades, it has been successfully applied in many areas of the earth and environmental sciences. However, there have been very few applications of this approach to active open pit mines in tropical environments. In this work, the DInSAR technique was applied to detect and monitor unknown surface displacements that may be occurring in the N4W iron mine, northern Brazil. X-band data acquired from March 2012 to April 2013 during the TerraSAR-X satellite mission were utilized for this purpose. The results were checked in the field and compared to optical leveling data. Due to the consistent deformation pattern observed over a mine waste pile, Pile W, we also performed numerical modeling in order to carry out a preliminary assessment of its theoretical deformation behavior. The results show that most of the study area can be considered to be stable. The numerical modeling indicated that horizontal displacements may be occurring, and that the DInSAR technique can be used to provide an initial rapid assessment of a large-scale deformation field, which could prove to be very useful, particularly in large active mining areas.

Mapping the flow pathways and contaminants transportation around a coal washing plant using the VLF-EM, Geo-electrical and IP techniques—A case study, NE Iran

Coal washing operation is now being carried out in the Alborz-Sharghi plant, located in northeast of Iran. This can in effect create a number of environmental problems. In this research, different geophysical surveys were conducted to investigate the leachate flow pathways and time-dependent transportation of contaminants in downstream of the plant which is situated between a coal waste pile and tailings impoundments. The very low frequency survey identified the most likely contamination zones and flow pathways. Furthermore, two-dimensional resistivity models obtained by the inversion of geoelectrical data (measured with the use of a dipole–dipole array incorporating a time-laps technique) showed the contaminated plumes with low resistivity values (<1 Ω m). To carry out a time-laps technique, 2-D geoelectrical surveys were repeated at same profiles by a time interval of 6 months. The results distinguished a time-dependent movement of the plume in a lateral and longitudinal form as well as its further extension to the deeper layers towards the groundwater table. This was also verified by the results obtained by the induced polarization measurements.

The properties of the nano-minerals and hazardous elements: Potential environmental impacts of Brazilian coal waste fire

Brazilian coal area (South Brazil) impacted the environment by means of a large number of coal waste piles emplaced over the old mine sites and the adjacent areas of the Criciúma, Urussanga, and Siderópolis cities. The area studied here was abandoned and after almost 30years (smokeless visual) some companies use the actual minerals derived from burning coal cleaning rejects (BCCRs) complied in the mentioned area for industry tiles or refractory bricks. Mineralogical and geochemical similarities between the BCCRs and non-anthropogenic geological environments are outlined here. Although no visible flames were observed, this study revealed that auto-combustion existed in the studied area for many years. The presence of amorphous phases, mullite, hematite and other Fe-minerals formed by high temperature was found. There is also pyrite, Fe-sulphates (eg. jarosite) and unburnt coal present, which are useful for comparison purposes. Bad disposal of coal-dump wastes represents significant environmental concerns due to their potential influence on atmosphere, river sediments, soils and as well as on the surface and groundwater in the surroundings of these areas. The present study using advanced analytical techniques were performed to provide an improved understanding of the complex processes related with sulphide-rich coal waste oxidation, spontaneous combustion and mineral formation. It is reporting huge numbers of rare minerals with alunite, montmorillonite, szomolnokite, halotrichite, coquimbite and copiapite at the BCCRs. The data showed the presence of abundant amorphous Si–Al–Fe–Ti as (oxy-)hydroxides and Fe-hydro/oxides with goethite and hematite with various degrees of crystallinity, containing hazardous elements, such as Cu, Cr, Hf, Hg, Mo, Ni, Se, Pb, Th, U, Zr, and others. By Principal Component Analysis (PCA), the mineralogical composition was related with the range of elemental concentration of each sample. Most of the nano-minerals and ultra-fine particles found in the burned coal-dump wastes are the same as those commonly associated with coal cleaning rejects, in which oxidation of sulphides plays an important role to environment and human health.

Environmental Geochemistry and Acid Mine Drainage Evaluation of an Abandoned Coal Waste Pile at the Alborz-Sharghi Coal Washing Plant, NE Iran

In this paper, an abandoned waste coal pile, which is resulted from Alborz-Sharghi coal washing plant, NE of Iran was mineralogically and geochemically characterized to evaluate pyrite oxidation, acid mine drainage (AMD) generation, and trace element mobility. After digging ten trenches and vertical sampling, a quantitative method including the atomic absorption test, and the quality-based methods including optical study were carried out for determination of pyrite fractions in the waste pile. The geochemical results revealed that the fraction of remaining pyrite increased with depth, indicating that pyrite oxidation is limited to the shallower depths of the pile which were confirmed by variations of sulfate, pH, EC, and carbonate with depth of the pile. To evaluate the trend of trace elements and mineralogical constituents of the waste particles, the samples were analyzed by using XRD, ICP-MS, and ICP-OES methods. The results showed the secondary and neutralizing minerals comprising gypsum have been formed below the oxidation zone. Besides, positive values of net neutralization potential indicated that AMD generation has not taken in the waste pile. In addition, variations of trace elements with depth reveal that Pb and Zn exhibited increasing trends from pile surface toward the bottom sampling trenches while another of them such as Cu and Ni had decreasing trends with increasing depth of the waste pile.

Chemical and mineralogical changes of waste and tailings from the Murgul Cu deposit (Artvin, NE Turkey): implications for occurrence of acid mine drainage.

Being one of the largest copper-producing resources in Turkey, the Murgul deposit has been a source of environmental pollution for very long time. Operated through four open pits with an annual production of about 3 million tons of ore at an average grade of about 0.5% Cu, the deposit to date has produced an enormous pile of waste (exceeding 100 million tons) with tailings composed of 36 % SiO2, 39% Fe2O3 and 32% S, mainly in the form of pyrite and quartz. Waters in the vicinity of the deposit vary from high acid-acid (2.71-3.85) and high-extremely metal rich (34.48-348.12 mg/l in total) in the open pits to near neutral (6.51-7.83) and low metal (14.39-973.52 μg/l in total) in downstream environments. Despite low metal contents and near neutral pH levels of the latter, their suspended particle loads are extremely high and composed mainly of quartz and clay minerals with highly elevated levels of Fe (3.5 to 24.5% Fe2O3; 11% on average) and S (0.5 to 20.6% S; 7% on average), showing that Fe is mainly in the form of pyrite and lesser hematite. They also contain high concentrations of As, Au, Ba, Cu, Pb, and Zn. Waters collected along the course of polluted drainages are supersaturated with respect to Fe phases such as goethite, hematite, maghemite, magnetite, schwertmannite and ferrihydrite. Secondary phases such as Fe-sulphates are only found near the pits, but not along the streams due to neutral pH conditions, where pebbles are covered and cemented by Fe-oxides and hydroxides indicating that oxidation of pyrite has taken place especially at times of low water load. It follows, then, that the pyrite-rich sediment load of streams fed by the waste of the Murgul deposit is currently a big threat to the aquatic life and environment and will continue to be so even after the closure of the deposit. In fact, the oxidation will be enhanced and acidity increased due to natural conditions, which necessitates strong remedial actions to be taken.

Modification, adsorption, and geochemistry processes on altered minerals and amorphous phases on the nanometer scale: examples from copper mining refuse, Touro, Spain.

The sulfide oxidation and precipitation of Al-Fe-secondary minerals associated with abandoned acid mine drainage (AMD) from the abandoned copper mine waste pile at Touro, Spain, has been studied by sequential extraction (SE) combined with several techniques with the intent of understanding the role of these processes play in the natural attenuation of hazardous element contaminants in the AMD. In addition, the fragile nature of nanominerals and ultrafine particle (UFP) assemblages from contaminated sediment systems from the abandoned copper mine required novel techniques and experimental approaches. The investigation of the geochemistry of complex nanominerals and UFP assemblages was a prerequisite to accurately assess the environmental and human health risks of contaminants and cost-effective chemical and biogeological remediation strategies. Particular emphasis was placed on the study and characterization of the complex mixed nanominerals and UFP containing potentially toxic elements. Nanometer-sized phases in sediments were characterized using energy-dispersive X-ray spectrometer (EDS), field-emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM) images. The identification of the geochemical and mineralogical composition of AMD in Touro, as well as the different formation mechanisms proposed, complement the existing literature on secondary mineral assemblages and provide new emphasis to increase the understanding of extreme environments. The results also demonstrated that variations in the geochemical fractionation of hazardous elements in AMD were more influenced by the secondary mineral proportion and by AMD pH.

Detecting the Source of Contaminant Zones Down-Gradient of the Alborz Sharghi Coal Washing Plant Using Geo-electrical Methods, Northeastern Iran

Environmental contamination from the Alborz Sharghi coal washing plant in northeast Iran was evaluated with geo-electrical techniques. The internal structure of a coal waste pile was first studied using one dimensional geo-electrical techniques, including a Schlumberger array. The oxidised zone had low resistivity while the unoxidised shallower and middle to deeper levels had higher resistivity. Next, the geo-electrical surveys were repeated after 6 months to investigate possible changes in the oxidation zone associated with seasonal variations. Precipitation affected the shallower levels of the pile. Two dimensional geo-electrical surveys, including a dipole–dipole array, were then conducted between the pile and tailings impoundments. Low resistivity values in the area appeared to indicate contaminated zones at depth. Again, two surveys were conducted at a 6 month interval. Results indicate the transportation of contaminants to deeper layers due to atmospheric precipitation. Considering the expansion of the contamination zones, the results of prior chemical analysis of the tailings impoundment water, and the increasing trend of the resistivity values in the deeper layers of the pile, seepage from the tailings impoundment is the most likely source of pollution in the area.

Colloidal mobilization of arsenic from mining-affected soils by surface runoff.

Scorodite-rich wastes left as a legacy of mining and smelting operations pose a threat to environmental health. Colloids formed by the weathering of processing wastes may control the release of arsenic (As) into surface waters. At a former mine site in Madrid (Spain), we investigated the mobilization of colloidal As by surface runoff from weathered processing wastes and from sediments in the bed of a draining creek and a downstream sedimentation-pond. Colloids mobilized by surface runoff during simulated rain events were characterized for their composition, structure and mode of As uptake using asymmetric flow field-flow fractionation coupled to inductively plasma mass spectrometry (AF4-ICP-MS) and X-ray absorption spectroscopy (XAS) at the As and Fe K-edges. Colloidal scorodite mobilized in surface runoff from the waste pile is acting as a mobile As carrier. In surface runoff from the river bed and the sedimentation pond, ferrihydrite was identified as the dominant As-bearing colloidal phase. The results from this study suggest that mobilization of As-bearing colloids by surface runoff may play an important role in the dispersion of As from metallurgical wastes deposited above ground and needs to be considered in risk assessment.

Novel and Unexpected Microbial Diversity in Acid Mine Drainage in Svalbard (78° N), Revealed by Culture-Independent Approaches.

Svalbard, situated in the high Arctic, is an important past and present coal mining area. Dozens of abandoned waste rock piles can be found in the proximity of Longyearbyen. This environment offers a unique opportunity for studying the biological control over the weathering of sulphide rocks at low temperatures. Although the extension and impact of acid mine drainage (AMD) in this area is known, the native microbial communities involved in this process are still scarcely studied and uncharacterized. Several abandoned mining areas were explored in the search for active AMD and a culture-independent approach was applied with samples from two different runoffs for the identification and quantification of the native microbial communities. The results obtained revealed two distinct microbial communities. One of the runoffs was more extreme with regards to pH and higher concentration of soluble iron and heavy metals. These conditions favored the development of algal-dominated microbial mats. Typical AMD microorganisms related to known iron-oxidizing bacteria (Acidithiobacillus ferrivorans, Acidobacteria and Actinobacteria) dominated the bacterial community although some unexpected populations related to Chloroflexi were also significant. No microbial mats were found in the second area. The geochemistry here showed less extreme drainage, most likely in direct contact with the ore under the waste pile. Large deposits of secondary minerals were found and the presence of iron stalks was revealed by microscopy analysis. Although typical AMD microorganisms were also detected here, the microbial community was dominated by other populations, some of them new to this type of system (Saccharibacteria, Gallionellaceae). These were absent or lowered in numbers the farther from the spring source and they could represent native populations involved in the oxidation of sulphide rocks within the waste rock pile. This environment appears thus as a highly interesting field of potential novelty in terms of both phylogenetic/taxonomic and functional diversity.