Evaluation of the long term groundwater pollution by the open cast lignite mine Jänschwalde (Germany)

The reconstruction of the hydrogeochemical composition of the dumps in the active Lusatian lignite mining region is necessary to forecast the acid mine drainage into the residual lakes and the natural groundwater systems. Therefore, a three-dimensional geochemical model of the Jänschwalde dump was developed. By analysing the geological situation and the mining technology, it is possible to calculate the pyrite oxidation in different parts of the mine (groundwater lowering in front of the mine, natural and dump slopes, marginal pits and the dump surface).Only 4% of the total pyrite content is oxidised during the mining process within its time of operation (43 years). The major fraction (about 60%) is oxidised on the surface of the dumps, whereas the other zones contribute less to the production of acidity (groundwater lowering 5.4%, short term exposed slopes (1.2% natural slopes; 7.4% dump slopes) and 22.4% inclusion of O₂ during the tipping). It may be concluded that the technology of conveyor belt bridges, combined with the selective tipping of loamy sediments on the surface is very favourable to minimise the oxidation of pyrite. It is also shown that in the open cast mine of Jänschwalde the buffer capacity of the carbonate dominates over the produced acid.     

Carbon dioxide treatment of low density sludge: a new remediation strategy for acidic mining lakes?

Acid mine drainage (AMD) is treated at several points in the Lausitz lignite mine district (Saxony, Germany) in treatment plants. The remaining alkaline low density sludge (LDS) was deposited in acidic mining lakes without having an impact on the lake water quality. Batch experiments show that alkalinity can be raised using LDS from acid mine drainage treatment plants together with CO₂. Batch experiments were conducted using lake water and deposited LDS from the mining lake Spreetal-Nordost with varying concentrations of CO₂. Also the duration of gas contact as well as the LDS–water ratio was changed in the batch experiments. The gas contact time and the partial pressure of CO₂ are the relevant parameters controlling the alkalinity in the lake water at the end of the experiments. The Ca and Mg concentrations of the pore water are relevant for higher pH values. Therefore, dissolved CO₂ can form bicarbonate or carbonate complexes, thus alkalinity rises. A second factor for alkalinity gain is the calcite content of the sludge, because CO₂ triggers the dissolution of carbonates. Therefore, unused calcite in the sludge can raise the alkalinity more effectively by the application of carbon dioxide. Furthermore, it was shown that remobilization of trace elements will not affect the water quality.     

Light Rare Earth Elements enrichment in an acidic mine lake (Lusatia,Germany)

The distribution of Rare Earth Elements (REE) was investigated in the acidic waters (lake and groundwater) of a lignite mining district (Germany). The Fe- and SO₄-rich lake water (pH 2.7) displays high REE contents (e.g. La∼70 μg/l, Ce∼160 μg/l) and an enrichment of light REE (LREE) in the NASC normalised pattern. Considering the hydrodynamic model and geochemical data, the lake water composition may be calculated as a mixture of inflowing Quaternary and mining dump groundwaters. The groundwater of the dump aquifer is LREE enriched. Nevertheless, the leachates of dump sediments generally have low REE contents and display flat NASC normalised patterns. However, geochemical differences and REE pattern in undisturbed lignite (LREE enriched pattern and low water soluble REE contents) and the weathered lignite of the dumps (flat REE pattern and high water soluble REE contents) suggest that lignite is probably the main REE source rock for the lake water.     

Evolution of organic matter in lignite-containing sediments revealed by analytical pyrolysis (Py–GC–MS)

Newly vegetated sites provide opportunities to enlighten organic matter (OM) transformation mechanisms in soils and sediments at very early stages of development which, in turn, is relevant to better understand general ecosystem functioning. Mine acid soils and sediments in the Lusatian open cast lignite mining district (Germany) contains a high concentration of fossil carbon (lignite) in ad mixture with recent OM from the local vegetation, both contributing to the humified OM pool. In this study, analytical pyrolysis (Py–GC–MS) was used to monitor the different C sources (lignite or plant derived) in developing mine tailing soils and sediments and their degree of degradation in contrasting environments. Representative vegetation and the organic carbon (OC) rich soil/sediment fraction (humus fraction) were sampled at two depths (0–5 and 5–10 cm) in three plots along a transect covering an upland forest soil, a partially submerged sediment at the land–water interface and a constantly submerged sediment. The analysis of plant (lipds, isoprenoids, methoxyphenols and carbohydrates) and possible lignite (alkyl napththalenes, alkyl benzenes and PAHs) biomarkers released after pyrolysis supports previous findings in the area using other proxies. It was possible to discern OM sources in soil/sediment humus fractions, both from the substrate (lignite) as well as from the prevailing vegetation of the area. Environmental conditions in the submerged sediment seem to favour OM protection and the accumulation of decomposing plant material, whereas more intense OM degradation seems to prevail in the land–water interface areas characterized by fluctuating water level. In addition, a well resolved series of organic sulfur compounds (OSCS) found in the submerged sediments of rehabilitated acid lakes, indicates the possible occurrence of particular mechanisms of C preservation in this extreme anoxic S rich environment, i.e. via sulphur “quenching” with plant derived lipids during early diagenesis.     

Detecting the footprint of a longwall mine panel claimed to infringe on a permit boundary at the Soma–Darkale coalfield (Manisa, Turkey) using surface fractures and microgravity measurements

A coal mine panel claimed to infringe on a permit boundary, or to create an hazard after subsidence has been the subject of lawsuits. We study at the Soma–Darkale coalfield (Manisa, Turkey), the footprint of a lignite coal mine panel at a depth of about 150–200 m by mapping all of the surface fractures we could observe, and by developing a post-subsidence density model that we verified through gravity measurements with positive Bouguer anomaly. With the analysis of the fracture map and the gravity data, we were able to identify the footprint of a mine panel from the effect of the anomalous mass due to denser overburden material filling up the space after the extraction of less-dense lignite. Whereas, using empirical methods like the so-called “limit line approach” to evaluate the extent of the area where mining can have subsidence-induced surface fracturing, one could not recognize for certain infringement of permit boundaries. The orientations of the fractures we mapped at the ground surface, the Bouguer gravity map, and a test borehole indicated the presence and dimensions of a coal panel in dispute. The presented approach based on gravity method and fracture observations may be an example to help settle conflicts related to the position of the longwall mine panel.     

SPOT5卫星影像在矿山环境调查中的应用

以吉林省辽源市煤炭矿山为研究对象,通过对SPOT5卫星影像纠正、融合、解译等处理,快速、便捷地查清矿区的地质环境问题:矿区固体废物堆放、尾矿库分布情况;矿山采空区地面塌陷、山体开裂、滑坡、崩塌、泥石流、岩溶塌陷、煤田自燃等地质灾害分布情况;由矿产开发引发的水土流失、土地沙化、侵占土地、植被破坏的情况;矿区水体、植被、土壤污染状况等。通过矿山地质环境调查实践,总结出了SPOT5卫星影像最优波段组合、融合方法及矿山地质环境调查中的地物判读标志,从而使SPOT5卫星影像在遥感环境地质调查中发挥了重要作用。     

Effects of mining subsidence on masonry buildings in Zonguldak hard coal region in Turkey

Gallerias are the underground constructed results of mining. As these space in underground layers collapse, horizontal and vertical ground movements occur and movement which may reach the earth’s surface are known as mining subsidence. The result of underground displacement may cause surface ground movement which can be detrimental to masonry buildings especially in hard coal regions. Thorough familiarity with general and regional characteristics of an affected area can assist reduction of the effects. Zonguldak and the nearby settlement area, with a population of 300,000, constitute the centre of a hard coal basin where extensive mining has a history extending through 160 years. Mining constitutes the main economic activity in this region, and consequently influences every aspect of life. This study’s intent is to identify the effects of mining subsidence on masonry buildings in the mining area of Kozlu, Zonguldak, Turkey and illustrate them with selected images of damaged masonry buildings. Also included are satellite and mining galleria images.     

基于高分二号卫星数据的煤矿区地质灾害信息提取研究

随着遥感数据获取技术和能力的全面提高,遥感数据呈现出明显的大数据特征。发展适应于遥感大数据的智能分析和信息挖掘技术,成为当前遥感技术研究的前沿。高分二号（GF-2）卫星数据是我国首颗自主研发的亚米级高分辨率卫星数据,具有观测幅宽、重访周期短、高辐射精度、高定位精度等优势,为未来我国地质灾害的长期、动态地监测和研究提供了高精度、稳定可靠的数据源。本文选取安徽谢桥煤矿2015年1月8日的GF-2卫星影像为研究数据,在对煤矿区主要地质灾害遥感地学分析的基础上,采用面向对象的影像分析方法对研究区由采煤活动所诱发的地质灾害信息进行自动提取。结果表明：利用GF-2卫星数据能够有效地识别地质灾害体的位置、范围、形态等空间分布特征;面向对象的自动提取方法对于煤矿区大面积的积水塌陷盆地、小规模的塌陷坑和线性的地裂缝都有很高的提取精度,识别精度达90% 以上;基于逐层剔除的思路构建的提取规则,为GF-2数据在地质灾害调查和大数据分析中的应用提供了很好的技术支持,也为其它地物目标的提取提供了参考,但在特征的选择和阈值的设定上需要具体分析。     

国内外矿井水处理及资源化利用研究进展

煤矿区矿井水处理及资源化利用是实现煤炭工业高质量发展与矿区生态文明建设双重目标的重要推力。在全球水资源短缺与生态环境保护的约束下,矿井水作为一种非常规水资源,其大规模处理与高效利用是未来发展的必然选择。文中从煤矿区矿井水水质特征出发,全面论述了矿井水水质形成机制与水质评价方法,并将矿井水水质形成划分为含水层水–岩作用和采空区水–岩作用2个阶段。系统分析了国内外含悬浮物矿井水、高矿化度矿井水、酸性矿井水及含特殊组分矿井水处理技术优缺点,重点阐述了含悬浮物矿井水高效旋流净化、高矿化度矿井水双极膜和膜蒸馏处理、酸性矿井水人工湿地处理的新技术。在总结国内外矿井水资源化利用现状的基础上,阐明了矿井水资源化利用的途径主要包括工业生产用水、生态用水、生活用水及热能利用4种。最后,提出了目前我国煤矿区矿井水处理及资源化利用存在的问题及科学思考,建立了矿井水处理及资源化利用概念模型,通过不断推进矿井水处理及资源化利用技术研发,提高矿井水资源综合利用率,解决煤矿区水资源供需矛盾,促进社会经济增长、煤炭资源开发与矿区生态文明建设三者之间的协同发展。     

利用光学卫星遥感数据监测抚顺地区煤矿开采引起的地貌变化

抚顺市是中国重要的采煤城市之一,100多年的煤矿开采已经使抚顺地区的地貌特征发生了重大变化。由于长期的露天开采,抚顺西露天矿形成了一个海拔约为-300m的深坑;煤矿的地下开采造成了大面积的地表沉陷;与此同时,煤矸石的露天堆积形成了3个排土场。本研究利用多时相的美国Landsat MSS（Multispectral Scanner）,TM（Thematic Mapper）,ETM⁺（Enhanced Thematic Mapper Plus）,以及日本ASTER（Advanced Spaceborne Thermal Emission and Reflection Radiometer）卫星遥感数据分析过去近30年来抚顺地区煤矿开采所引起的地貌变化。多时相卫星遥感图像的对比分析显示,由于地面沉陷引起的地表积水面积在近5年（2001～2006年）内出现明显增大的趋势,增加了1.73km。同期的ASTER DEM数据对比分析还发现,西露天矿的开采深度在不断增加,最大增加量为55m,与此同时出现的新增排土场造成地面高程增加量最大为25m。这一研究表明利用遥感技术可以定量监测人类矿产开发活动所引起的地貌特征变化及其过程。     

Use of mine spoils from Teruel coal mining district (NE,Spain)

Coal mine restoration projects increase public perception of mining companies. Spain has relatively few examples of completed opencast mine rehabilitation projects. This study seeks to obtain the use of mine spoils from coal mines in Teruel. The studied mine spoils may be used as raw material for the Spanish ceramic industry, located in the provinces of Castellon, Valencia and Teruel. This study specifically discusses the mineralogical and geochemical characteristics of the Lower Cretaceous materials from coal deposits in Estercuel basin, around Teruel and Castellon in Spain. These provinces have a large ceramic industry. A characterization of mine spoils from coal deposits has been carried out. This characterization is based on the data of both mineral and chemical analysis. The mineralogical characterization was complemented with SEM/EDAX. The study of the chemical composition allows the evaluation of the applicability of the studied mine spoils to the following industries: refractory, fine clay, red clay for pavement and coating, and heavy clay. The clay used for refractory industry has the highest compositional demand. The positive results obtained on this set of preliminary tests lead us to envisage new research programs, focusing on testing these mine spoils on a semi-industrial scale.     

Effect of coal mine waters of variable pH on springwater quality: A case study

Disruption of coal strata during mining accelerates pyrite oxidation by exposing greater surface areas of the reactive mineral to weathering. Acidic water in a coal mine in the Niangziguan spring watershed is related to this process and is characterized by low pH (min. 2.52) and high sulfate (max. 4100 mg/I), iron (max. 257 mg/I), and hardness (max. 2274.45 mg/I). However, it is possible that the kind of acidic coal mine water is subsequently neutralized because of the dissolution of calcite present in the coal strata. The hydrochemical characters of the alkaline coal mine water produced are high pH (max. 8.18), sulfate (max. 542 mg/I), and hardness (max. 1183.56 mg/I) and lower iron (min. 0.12 mg/I). Experiments were conducted to further understand the mechanism of the formation of both acidic and alkaline waters in the spring watershed coal mines by modeling natural conditions with simplification, and the results of the experiments have shown that they are basically successful. The high sulfate (max. 223.82 mg/I) and hardness (max. 435.53 mg/I) of the Niangziguan springs are related to the influence of the neutralized acid coal mine water as demonstrated by analysis of water temperature, total dissolved solid, Q-mode cluster analysis, and sulfur isotopes. The influence of the neutralized acid coal mine water on the pH and iron in the springs is not obvious because of the neutralization effect of calcite in aquifer, the buffer effect of groundwater, and the precipitation of iron. Some measures to prevent the formation of acid and alkaline coal mine water are presented.     

Reaction time scales for sulphate reduction in sediments of acidic pit lakes and its relation to in-lake acidity neutralisation

Sulphate reduction is a key reaction to remove acidity from water bodies affected by acid mine drainage. In this study, ³⁵SSO₄²⁻ reduction rates determined in sediments from a variety of acidic lignite pit lakes have been compiled. The rates decreased with pH and are strongly dependent on carbon substrate. The rates were fitted to a Monod model adapted to the specific conditions of acidic pit lakes (APL) sediments: i) sulphate reduction rate is independent from sulphate concentration due to the high concentration typically observed in APL systems (10–30 mM), ii) the observed pH dependency of sulphate reduction was accounted for by an inhibition function F_inihibt which considers the occurrence of low cell numbers of sulphate reducing bacteria at pH values < 4.75. Simulated steady-state sulphate reduction rates are predicting measured rates at carbon substrate concentrations of <10 μM. Estimated steady-state reaction time scales range between 2.4 h at pH 7 and 41 h at pH 3 at a carbon half-saturation constant of K_C−S = 100 μM and are increasing with increasing K_C−S values. Time scales at low pH are too long to allow for significant generation of alkalinity during the time of residence of groundwater passing through the top and hence most reactive zone of APL sediments which has important implications for the remediation of acidic pit lakes.     

Characteristic of water chemistry and hydrodynamics of deep karst and its influence on deep coal mining

The mining depth of main coal mines could reach around 600 m in eastern North China, and extends to the dept with speed of around 12 m/a. As the basement of eastern North China-type coal mine, the Ordovician karst aquifer is the main water source that influences the carboniferous coal seam mining. As the deep karst water has large buried depth and high water pressure (8–12 MPa), with10–30 m space between high pressure aquifer and coal seam, the geological area of deep coal occurrence is often forbidden for mining. Environmental damage, to a greater or lesser degree, is caused by coal mining. On the basis of analyzing the hydrogeological conditions of mining areas, this paper introduces the hydrogeological survey work of ultra-high confined karst water deep in the coal seam floor within researched region for preventing and controlling water disaster of the mine. After researching into the hydrogeological investigation data in the researched region, we explored the hydrodynamic and water chemical characteristics of deep karst water by using pumping test, dynamic observation, and dewatering test. Finally, this study suggests that the hydraulic pressure of deep mining could be mined, on the circumstances that reasonable and effective of water prevention measures are taken based on a detailed survey on water abundance of deep karst.     

An integrated technology for gas control and green mining in deep mines based on ultra-thin seam mining

With the increasing demand for coal resources, coal mining has gradually entered into the deep strata of coal seams. Although the increase in mining depth improves energy security, it is associated with severe hazards, especially coal and gas outburst. Protective seam mining is an efficient method for gas control and has been widely used in major coal-producing countries. However, studies on deep ultra-thin protective seam (thickness 0.1–1 m, average thickness 0.5 m) mining and its related problems have been rarely reported. Focusing on the challenges resulting from deep mining (mining depth >1100 m) and the research gap, a coal and gas co-exploitation technique, which combines the gas control technology and green mining (including coal preparation and backfilling), has been proposed in this work. Significant benefits have been achieved in the twelfth coal mine of the Pingdingshan coalfield (study area) following the implementation of this technique. The application of the gas control technology markedly improved the gas drainage efficiency, promoted increased gas utilization, and reduced the greenhouse gas emission, providing notable economic and environmental benefits. In addition, implementation of green mining improved the coal quality, relieved the burden of the transport system, and, in particular, effectively prevented surface subsidence, thus protecting the ecological environment of the mining area, which offered significant economic, environmental, and social benefits. The practice in the twelfth coal mine could be used as a valuable example for coal mines with similar geological conditions.     

Fracture Evolution and Accumulation and Dissipation Law of Energy During Ascending Mining

Ascending mining method is a widely used method in China for coal mine safety. To determine whether ascending mining method can eliminate or reduce the outburst risk or not in Xinzyao Mine, China, a numerical model was built by FLAC3D software to investigate the fracture evolution and accumulation and dissipation law of energy during the process of ascending mining. And a dual water blocking system was used to verify the fracture evolution obtained from the numerical model. The results show that FLAC3D model can predict the fracture evolution in overburden with a reasonable error. The height of water-conducting fractured zone of no. 14-3 coal seam is about 82.5 m, and it increases by 27 % after no. 12-2 coal seam is mined. The largest energy accumulated in no. 12-2 coal seam is about 32.5 kJ/m³ when mining it directly. The energy accumulated in no. 12-2 coal seam decreases by more than 40 % when ascending mining method is adopted. Ascending mining method can effectively eliminate the outburst risk of the upper coal seam. The research is helpful for the determination of ascending mining method and the further study of the prevention mechanism of rock burst.     

Research and application of roadway backfill coal mining technology in western coal mining area

In China’s western coal mining area, the traditional room mining technology is facing coal pillar instability, mine earthquake, large-area roof subsidence in the goaf, surface subsidence, water and soil loss, vegetation deterioration, and other environmental problems. To solve the aforementioned problems and to improve coal recovery, the roadway backfill coal mining (RBCM) method was proposed as a solution and its technical principle and key equipment were presented in this paper. In addition, the microstructure and mechanical behavior (strain-stress relation in confined compressive test) of aeolian sand and loess backfill materials were studied for a rational backfill design for underground mines. Further, coal pillar stress, plastic zone change, and surface deformation of the RBCM schemes were studied using the FLAC^3D numerical simulation software, and a reasonable mining scheme of “mining 7 m and leaving 3 m” was determined. The engineering application in Changxing Coal Mine shows that the RBCM method with loess and aeolian sand as backfill materials allows a stable recovery of coal pillars with a recovery ratio of more than 70 %. The maximum accumulated surface subsidence and the maximum horizontal deformation were measured to be 15 mm and 0.8 mm/m respectively, indicating that the targeted backfilling effect can help protect the environment and also control surface subsidence.     

Tracing the interaction of acid mine drainage with coal utilization byproducts in a grouted mine: Strontium isotope study of the inactive Omega Coal Mine,West Virginia (USA)

In order to ameliorate acidic discharge, the inactive Omega Coal Mine, West Virginia was partially filled by injection of a grout consisting of 98% coal utilization byproducts (CUB), including fluidized bed combustion ash and fly ash, and 2% Portland cement. In this study, discharge chemistry and Sr isotope ratios were determined to identify and quantify the extent of interaction between mine waters and the CUB–cement grout. Eight sampling sites were monitored around the downdip perimeter of the mine. The major and trace element chemistry of the discharges was generally not sufficient to distinguish between discharges that interacted with grout and those that did not. Elements that showed the most separation include K and As, which were elevated in some waters that interacted with CUB–cement grout. In contrast, the Sr isotope ratios clearly distinguished discharges from grouted and non-grouted areas. Discharges that bypassed the grouted portions had ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.71510 to 0.71594, while two discharges that interacted with grout had ratios in the range of 0.71401–0.71456. The Treatment Inlet, which includes both grouted and ungrouted discharges, yielded intermediate isotopic ratios. Leaching experiments on CUB–cement grout, coal and surrounding rocks are consistent with the isotopic trends observed in the discharges. Based on these results, waters that interacted with grout received 30–40% of their Sr from the CUB–cement grout material. These results suggest that the grout material is chemically eroding at a rate of approximately 0.04% per year. This novel application of the Sr isotope system illustrates its ability to sensitively track and quantify fluid interaction with coal and CUB-based grout.     

Mapping and detection of land use change in a coal mining area using object-based image analysis

Object-based image analysis was used to map land use in the Panxie coal mining area, East China, where long-term underground coal mines have been exploited since the 1980s. A rule-based classification approach was developed for a Pleiades image to identify the desired land use classes, and the same rule-based classification strategies, after the threshold values had been modified slightly, were applied to the Landsat series images. Five land use classes were successfully captured with overall accuracies of between 80 and 94%. The classification approach was validated for its flexibility and robustness. Multitemporal classification results indicated that land use changed considerably in the Panxie coal mining area from 1989 to 2013. The urban, coal and coal gangue, and water areas increased rapidly in line with the growth in mine production. Urban areas increased from 9.38 to 20.92% and showed a tendency to increase around the coal mines. From 1989 to 2013 the coal and coal gangue area increased by 40-fold, from 0.02 to 0.58%. Similarly, the water area increased from 2.77 to 7.84% over this time period, mainly attributable to the spread of waterlogged areas. The waterlogged areas increased to about 2900 ha in 2013, which was about 80 times more than their area in 1989. In contrast, the area of cultivated land was negatively related to the increase in mine production and decreased from 73.11 to 57.25%. The results of this study provide a valuable basis for sustainable land management and environmental planning in the Panxie coal mining area.