Coal Waste Dumps Research Articles

COMPREHENSIVE PROCESSING OF MINERAL RAW MATERIALS FROM COAL MINE WASTE DUMPS: PROPERTIES, VALUABLE PRODUCTS, AND RESOURCE ACCOUNTING SYSTEM

Objective. Experimental studies on the chemical and mineralogical composition of coal mine spoil heaps and the potential for processing them to obtain valuable mineral-raw materials. Development of an analytical tool for accounting and forecasting the resource potential of coal mine spoil heaps. Methods. To achieve the objective, X-ray fluorescence analysis, X-ray phase analysis, granulometric analysis, laboratory studies of mineral raw material enrichment using sieve fractionation and gravity separation, as well as analytical studies of spoil heap resource accounting were employed. Results. The chemical, mineralogical, and granulometric composition of spoil heaps from a coal mine in the Western Donbas region was investigated, enabling the identification of a processing strategy to obtain a range of products: coal concentrate, crushed stone mixture, sand fraction, and clay fraction. It was established that gravity separation of coarse fractions in a heavy medium created with clay slurry demonstrated high separation efficiency, yielding a significant low-ash coal fraction and a high-ash rock fraction. In contrast, spiral separator processing demonstrated significantly lower low-ash coal recovery. A technological processing scheme for spoil heaps to obtain a complex of valuable products was developed, and forecast indicators were evaluated. A methodological system for accounting the resource potential of a coal mine waste dump has been proposed in the form of an informational database. This system allows for tracking changes in the dumps structure, identifying zones of attractive resource accumulation for economic efficiency of processing operations in the long term. Scientific novelty. The use of clay suspension from washed spoil heaps to create a heavy medium for the beneficiation of coarse fractions allows for the recovery of up to 95% coal concentrate with 11% ash content, contributing to resource conservation. Practical significance. A technological scheme for obtaining a range of valuable products for the energy and construction industries has been developed. An analytical tool for resource potential accounting and calendar planning for spoil heap formation has been created, enabling operational identification of resource concentration zones within spoil heaps and their sections. Keywords: coal mine, spoil heap, valuable resource, chemical composition, mineralogical composition, granulometric composition, gravity separation, resource accounting.

Element Cycling at Thermally Active Coal-Waste Dumps: A Case Study of Calamagrostis epigejos and Solidago canadensis

Coal-waste dumps in the Upper Silesian Coal Basin are usually colonized by tall grass Calamagrostis epigejos and Solidago canadensis, which influence the direction of vegetation formation and the soil chemistry. The aim of this study is to analyze and determine the content of major elements (Fe, Ca, P, Mg, Al, Na, K, S) and trace elements (Mo, Cu, Pb, Zn, Ni, Co, Mn, Sr, Cd, Cr) in aboveground and underground parts of the plants and the soil at the thermally active coal-waste dump. Analysis of the heavy metal concentrations reveals that they are higher in plant materials than in soil materials within the root zone of the plants. Environmental indicator analysis (geoaccumulation index, enrichment factor, translocation factor) shows that the studied species exhibit varying degrees of pollution, with cadmium and zinc showing the highest accumulation rates. The content of elements in the analyzed species, both in washed and unwashed specimens, does not show significant differences, which is confirmed by the enrichment factor. Statistical analysis shows a positive correlation between the amount of microelements in plants (roots, aerial part) and soil samples in both thermally active and inactive zones. These findings broaden the scientific inquiry and hold practical significance for the reclamation of post-industrial areas.

Botryoidal and spherulitic hematite as experimental evidence of highly acidic conditions in burning coal-waste dumps and potentially on Mars

In the extreme setting of burning coal-waste dumps in the Upper Silesian Coal Basin in Poland, botryoidal and spherulitic hematite occurs in association with sulphates and chlorides. A series of simple experiments aimed at replicating the conditions leading to the formation of hematite spherules on the burning dumps are described. Goethite synthesised in the laboratory, mixed with various combinations of other reactants, was heated in a heating chamber or a tubular furnace. Temperature, duration of heating, water and oxygen access, and pH were experimental variables. The results show that hematite may form spherules from goethite where access to oxygen is limited and where conditions are strongly acidic. The spherulitic shape of hematite produced due to dynamically changing physicochemical conditions in the burning dumps can be an indicator of an extremely acidic environment during the closing stages of coal-waste self-heating. The conditions of hematitic-spherule formation on burning coal-waste dumps may apply in a variety of other unrelated settings, e.g., waning volcanism, sulphuric acid speleologenesis and even the formation of blueberries on Mars.

WITHDRAWN: The evaluation model for factors affecting soil quality in waste dumps open-pit coal waste dumps based on fuzzy mathematics

Taking the Hequ open-pit coal mine waste dump as the research object, using the fuzzy analytic hierarchy process and expert scoring theory, 4 criteria and 25 factors were established, including the evaluation model of soil structure stability, soil water retention capacity, soil fertilizer retention capacity, soil biological activity, and factors affecting soil quality in the waste dumps. Using YAAHP calculation software, the weights of various influencing factors on the soil fertility restoration ability of the waste dumps were determined. Combining a fuzzy comprehensive evaluation method to determine soil nutrient standards, soil quality evaluation is divided into 5 levels, and the main influencing factors of soil restoration ability in open-pit coal mine waste disposal sites are quantitatively analyzed. The results showed that: The weight of soil fertility in the criterion layer of the evaluation model was the largest (0.548), followed by soil water retention capacity (0.198), soil biological activity (0.140), and soil structural stability (0.114). The weight of organic matter F1 in the factor layer was the highest (0.116). Due to the final evaluation score of the soil recovery ability of the target layer open-pit coal mine waste dumps is 53.584, the soil quality and nutrients of the waste dumps are in the middle level. The main factors of soil resilience are soil fertility and soil organic matter content, to provide management strategies for improving soil quality of dump, accelerating soil reconstruction, and promoting soil ecosystem restoration.

Unmanned Aerial Vehicle (UAV)-Based Vegetation Restoration Monitoring in Coal Waste Dumps after Reclamation

Frequent spontaneous combustion activities restrict ecological restoration of coal waste dumps after reclamation. Effective monitoring of vegetation restoration is important for ensuring land reclamation success and preserving the ecological environment in mining areas. Development of unmanned aerial vehicle (UAV) technology has enabled fine-scale vegetation monitoring. In this study, we focused on Medicago sativa L. (alfalfa), a representative herbaceous vegetation type, in a coal waste dump after reclamation in Shanxi province, China. The alfalfa aboveground biomass (AGB) was used as an indicator for assessing vegetation restoration. The objective of this study was to evaluate the capacity of UAV-based fusion of RGB, multispectral, and thermal infrared information for estimating alfalfa AGB using various regression models, including random forest regression (RFR), gradient boosting decision tree (GBDT), K-nearest neighbor (KNN), support vector regression (SVR), and stacking models. The main results are as follows: (i) UAV multi-source data fusion improved alfalfa AGB estimation accuracy, although the enhancement diminished with the increasing number of sensor types. (ii) The stacking model consistently outperformed RFR, GBDT, KNN, and SVR regression models across all feature fusion combinations. It achieved high accuracy with R2 of 0.86–0.88, RMSE of 80.06–86.87 g/m2, and MAE of 60.24–62.69 g/m2. Notably, the stacking model based on only RGB imagery features mitigated the accuracy loss from limited types of features, potentially reducing equipment costs. This study demonstrated the potential of UAV in improving vegetation restoration management of coal waste dumps after reclamation.

Effects of coal mine waste dump on soil seed bank and vegetation distribution pattern

Long-term occupation of coal gangue dumping sites (CGDS) may destroy ecological environment of nearby area. However, how the CGDS affects the distribution pattern of soil seed banks and vegetation in the nearby area is not clear. In this study, we investigated soil seed bank and vegetation at different distances from the second CGDS of Yangchangwan in Ningdong mining area, Lingwu, Ningxia. The results showed that soil seed bank was mainly distributed in 0-10 cm layer and decreased with increasing soil depth. Species richness of soil seed bank and vegetation first increased and then tended to be stable with increasing distance to the CGDS. The influence range of CGDS on soil seed banks was 300-500 m and was 100-300 m on aboveground vegetation. The CGDS did not affect the vertical distribution pattern of soil seed bank, but significantly affected the horizontal distribution pattern of soil seed banks and aboveground vegetation. The key area of vegetation restoration around the CGDS was between 100 m and 300 m.

Organic minerals in a self-heating coal-waste dump in Upper Silesia, Poland: Structure, formation pathways and environmental issues

The study presents research on the unusual appearance of purple-colored organic minerals, ravatite (phenanthrene) and freitalite (anthracene), occurring in the migrating front wall of a heating spot in the Bytom coal waste dump (Upper Silesia Coal Basin, Poland). These minerals are known to be sublimation products, but their formation mechanism remains unclear. Additional minor components are fluorene, dibenzothiophene, naphthothiophenes, dibenzofuran, and their alkyl-derivatives, and n-C17 – n-C20 alkanes. Temperatures were surprisingly low (30–60 °C on the surface) at the sampling sites, though such large amounts of Polycyclic Aromatic Hydrocarbons (PAHs) typically form in a burning environment where temperatures reach 800–1000 °C. The relatively low temperatures suggest that the primary mechanism of formation was not direct evaporation (desublimation) of phenanthrene and anthracene from coal-waste gases but that their occurrence may reflect a catalytical polymerization of ethylene on iron (III) chloride synthesized in a reaction between HCl and a common Fe mineral such as goethite. Subsequently, both minerals crystallized on the cold dump surface. High concentrations of phenanthrene and anthracene in self-heating products, testified by ravatite and freitalite, mean that self-heating of coal waste may significantly increase backgrounds of environmental pollution by PAHs.

Thermal signatures of relict coal spoil, waste and tailing dumps

ABSTRACT As relict features of coal mines, carbonaceous spoil, waste and tailing dumps remain susceptible to coal oxidation and thermal decomposition, together with spontaneous combustion. Modern methods for monitoring surface thermal signatures regularly include the use of UAV’s, equipped with suitably sensitive infrared cameras. Detection of sub-surface thermal anomalism includes Vegetation Index Monitoring and/or the use of in-ground probes. Research across thermally active tailings offers insights into how best apply these two techniques, and increasingly the required scheduling of UAV surveys.

Examining the effect of spontaneous combustion on vegetation restoration at coal waste dumps after reclamation: Taking Medicago sativa L. (alfalfa) as an indicator

The Spontaneous combustion problem poses a significant threat to the coal waste dumps after reclamation. Spontaneous combustion alters the soil environment and further affects vegetation growth. Therefore, it is essential to understand the response of vegetation and soil to spontaneous combustion for ensuring vegetation restoration. Here, taking the reclaimed plant type, Medicago sativa L. (alfalfa), as an indicator, this study carried out a field survey in a typical spontaneous combustion area (study area) of a coal waste dump after reclamation. A total of 41 soil and 70 vegetation sampling points were investigated in the field survey, including soil environmental factors (soil temperature, ST; soil water content, SWC; soil organic carbon, SOC; total nitrogen, TN; available phosphorus, AP; available potassium, AK; bulk density, BD; pH) and alfalfa growth indicator (above-ground biomass, AGB). The spatial variation of alfalfa AGB reached 69.9 %, and all soil environmental factors showed moderate variation (12.28–35.03 %) except for BD and pH. ST was found to have a strong explanatory ability on the variation of AGB in the entire study area (q = 0.62, p < 0.01), but the ability weakened with the improvement of the health grades of alfalfa (Grades A, B, C, and D). From Grade D to Grade A, the q-value gradually reduced from 0.71 (p < 0.01) to 0.05 (no significance). The interaction effects of soil environmental factors showed mostly bilinear and non-linear enhancement. In regions with severe vegetation degradation (Grade C and Grade D of alfalfa), the interaction of ST with BD, AP, AK, and TN played a dominant role in the spatial variation of alfalfa AGB (44.8–86.15 %). However, in the regions of Grade A and Grade B, the spatial variation of alfalfa AGB was mainly affected by the interaction effects of AK, TN, AP, and SOC (60.13–84.77 %). As a simple analysis method, Geodetector can help researchers to better understand the complex response mechanism of vegetation-soil under spontaneous combustion of coal waste dump. This study provides a theoretical reference for vegetation restoration of coal waste dumps.

Iron colloidal transport mechanisms and sequestration of As, Ni, and Cu along AMD-induced environmental gradients

Colloids are common in mine waters and their chemistry and interactions are critical aspects of metal(loid)s cycling. Previous studies mostly focus on the colloidal transport of metal(loid)s in zones where rivers and soil profiles receive acid mine drainage (AMD). However, there is limited knowledge of the colloid and the associated toxic element behavior as the effluent flows through the coal waste dump, where a geochemical gradient is produced due to AMD reacting with waste rocks which have high acid-neutralization effects. Here, we investigated the geochemistry of Fe and co-occurring elements As, Ni, and Cu along the coal waste dump, in aqueous, colloidal, and precipitate phases, using micro/ultrafiltration combined with STEM, AFM-nanoIR, SEM-EDS, XRD, and FTIR analysis. The results demonstrated that a fast attenuation of H+, SO42−, and metal(loid)s happened as the effluent flowed through the waste-rock dump. The Fe, As, Ni, and Cu were distributed across all colloidal sizes and primarily transported in the nano-colloidal phase (3 kDa–0.1 μm). An increasing pH induced a higher percentage of large Fe colloid fractions (> 0.1 μm) associated with greater sequestration of trace metals, and the values for As from 39.5 % to 54.4 %, Ni from 40.8 % to 75.7 %, and Cu from 43.7 % to 56.0 %, respectively. The Fe-bearing colloids in AMD upstream (pH ≤ 3.0) were primarily composed of Fe–O–S and Fe–O–C with minor Al–Si–O and Ca–O–S, while in less acidic and alkaline sections (pH ≥ 4.1), they were composed of Fe–O with minor Ca–O–S. The iron colloid agglomerates associated with As, Ni, and Cu precipitated coupling the transformation of jarosite, and schwertmannite to ferrihydrite, goethite, and gypsum. These results demonstrate that the formation and transformation of Fe-bearing colloids response to this unique geochemical gradient help to understand the natural metal(loid)s attenuation along the coal waste dump.

Ecological restoration of coal mine waste dumps: A case study in Ximing Mine, China

ABSTRACT This study focuses on addressing the issues of spontaneous combustion and slope instability at the coal mine waste (CMW) dump located on the north side of the Yumen River in Ximing Mine, China. We conducted slope restoration and environmental treatment of the CMW dump using shotcrete, deep hole grouting, external soil spray seeding technology with multiple soil fixation measures. The stability of the repaired CMW dump was analysed using LiZheng Slope Stability Analysis Software, and the displacement and stress of high-risk zones were assessed using MIDAS GTS NX Software. Our findings provide valuable insights for slope restoration and evaluation.

Preservation of labile organic compounds in sapropelic coals from the Upper Silesian Coal Basin, Poland

Sapropelic coals were taken for study from coal mines and coal waste dumps in Upper Silesian Coal Basin (USCB), Poland. They showed unusual molecular compositions reflecting immature characteristics. The vitrinite reflectances 0.65-1.00% indicated mature organic matter (OM) and agreed with the Rock Eval Tmax (421-444oC). The OM maturity also was supported by the geochemical ratios, i.e., alkylnaphthalenes, dimethylphenanthrenes, methylbiphenyls and dibenzofuran or phenol and its methyl derivatives in the southern part of USCB. The petrographic features showed fine-grained and laminated OM, which is typical for sapropel with a dominance of vitrinite and inertinite macerals. The presence of fusinites and natural chars reflects paleowildfires prior to coal formation and/or peat fires. It is also confirmed by the presence of anthracene, methyl-anthracenes, and oxygen-containing aromatic compounds like anthrone, xanthone, fluorenone, and benzofluoren-11-ones. Rock Eval pyrolysis data showed very similar values as the humic coals from USCB, except for the elevated values of S2 (residual petroleum potential) and Hydrogen Index (HI) reflecting the presence of hydrogen-rich liptinite macerals. The distributions of n-alkanes, methylalkanes, alkylcyclohexanes and alkylbenzenes indicate a microbiological origin associated with microorganisms, including cyanobacteria or Botryococcus. In all samples 8β(H)-homodrimane dominated and indicated an anoxic environment of the deep lakes. The preservation of tetracyclic diterpenoids, diaster-13(17)-enes, ββ-hopanes, simonellite, bisnorsimonellite, cadalene, fatty acids, aromatic aldehydes and carboxylic acids from lignin degradation in sapropelic hard coals indicates an early diagenetic generation of these compounds from sapropels. Furthermore, during coalification, some the less thermally labile compounds can be preserved with increasing coal rank, while others isomerized or aromatized to more stable counterparts.

Slope Stability Numerical Analysis and Landslide Prevention of Coal Mine Waste Dump under the Impact of Rainfall—A Case Study of Janina Mine, Poland

In Poland, the mining waste from underground coal mines is commonly deposited in surface dump sites, forming slopes or piles of materials dozens of meters high. Because of the loose structure of a mine waste dump slope, landslides may occur after a heavy rainfall. This requires significant labor costs in reforming the mine waste dump sites and disturbs the continuity of the depositing operations. Moreover, if the mine waste dump sites located in the built-up areas, such as in the Janina mine waste dump, landslides apparently can threaten even lives and properties. Therefore, a mine waste dump stability analysis is necessary for ensuring safety. In this paper, slope stability analysis was conducted using numerical modeling under the impact of rainfall for the Janina mine waste dump, located in Libiąż, Poland. The results indicated that slope tends to loose stability in case of high rainfall intensity and short duration. Then, slope reinforcement using soil nailing and steel mesh was proposed to prevent landslide under the impact of high rainfall intensity. Once again, slope stability analysis was carried out with selected reinforcement. Meanwhile, slope monitoring was performed to assess the slope reinforcement implementation at the Janina mine waste dumps against the impact of high rainfall intensity. Based on the modeling and monitoring outcomes, assessments of slope stability and selected landslide prevention measures for the Janina mine waste dump under the impact of rainfall were presented.

Vegetation growth status as an early warning indicator for the spontaneous combustion disaster of coal waste dump after reclamation: An unmanned aerial vehicle remote sensing approach.

Spontaneous combustion of coal waste dumps is a serious threat to the ecological environment and the safety of mining areas. Even after land reclamation and ecological restoration, such spontaneous combustion activities are still active. Achieving early warning of spontaneous combustion is necessary to protect the reclaimed ecosystem and reduce environmental pollution, but it has not yet been well studied. To this end, this study proposed a spatial analysis method to achieve early warning spontaneous combustion of coal waste dump after reclamation by integrating unmanned aerial vehicle (UAV) and vegetation (Medicago sativa/alfalfa) growth status. The experiment was implemented in two slope areas (Areas I and II) of a coal waste dump after reclamation in Shanxi province, China, which were under threat of spontaneous combustion. Three alfalfa growth parameters, aboveground biomass (AGB), plant water content (PWC), and plant height (PH) of the study area, were estimated from UAV imagery features and used to assess the spontaneous combustion risk. Then, soil deep temperature points (25cm depth) distributed evenly in the study area were collected to determine the underground temperature situation. It was found that the UAV-derived rededge Chlorophyll index (CIrededge), canopy temperature depression (CTD), and canopy height model (CHM) achieved a better estimation of alfalfa AGB (R2=0.81, RMSE=99.2g/m2, and MAE=74.9g/m2), PWC (R2=0.68, RMSE=3.9%, and MAE=3.2%), and PH (R2=0.77, RMSE=9.79cm, and MAE=7.68cm) of the study area, respectively. We also observed that three alfalfa parameters were highly correlated with the soil deep temperature, but differed in degree (R2=0.46-0.81). Furthermore, they were consistent with the soil deep temperature in spatial distribution and could reveal the change direction of underground temperature, which will help us to detect those potential spontaneous combustion areas. These results indicated that vegetation is a prior indicator to the changes in underground temperature of coal waste dump. We believed that UAV can be an effective environmental management tool for the initial assessment of spontaneous combustion risk of coal waste dump after reclamation.

Monitoring potential spontaneous combustion in a coal waste dump after reclamation through unmanned aerial vehicle RGB imagery based on alfalfa aboveground biomass

AbstractSpontaneous combustion of coal waste dumps is one of the main problems in mining areas. This risk still exists even after land reclamation and ecological restoration. Once spontaneous combustion of a coal waste dump occurs after reclamation, it will lead to repeated land degradation and vegetation damage again. Focusing on this issue, a monitoring method using unmanned aerial vehicle (UAV) RGB imagery based on alfalfa aboveground biomass (AGB) is proposed in this study. Two areas of a coal waste dump that suffered spontaneous combustion of coal waste after reclamation in Shanxi Province, China, were selected as the study area. Combined with the vegetation index and texture metrics extracted from UAV RGB imagery, the AGB was estimated using stepwise linear regression models. Finally, the intensity of spontaneous combustion was classified based on alfalfa AGB. In this study, our results show that: (i) the AGB estimation accuracy can be improved by combining the spectral and texture features [R2 = 0.86, root mean square error (RMSE) = 0.09 kg /m‐2, and mean absolute error (MAE) = 0.08 kg m‐2]; (ii) alfalfa AGB had a good ability to explain the underground thermal anomalies based on the deep soil temperature; (iii) Compared with the land surface temperature, alfalfa AGB was more suitable for monitoring the potential spontaneous combustion areas, especially in the initial stage, where spontaneous combustion has occurred but does not have a significant impact on the land surface. This study was intended to provide an improved method for detecting the spontaneous combustion monitoring of coal waste dumps, which may provide a reference for initial monitoring and prevention in mining areas.

Microbiota of the rhizosphere zone of Calamagrostis epigeios from a coal mine waste dump

The microbiota plays an important role in the processes of plant overgrowth of coal mine waste dumps, enabling the transformation of numerous compounds into forms available to plants. The overgrowth of coal mine dumps is influenced by many factors. Pioneers are plant species that have a wide ecological and phytocenotic amplitude. Calamagrostis epigeios (L.) Roth. occupies a special place among them. The composition of the microbiota of the rhizosphere zone of C. epigeios was studied in relation to the age of the plants and the stage of the succession of the “Vizeyska” mine dump (Ukraine). It was established and confirmed as a result of two-factor variance analysis that the growth phase of C. epigeios and the stage of the succession of coal mine waste dumps have different effects on the number of microorganisms from the rhizosphere zone of plants. The number of pedotrophic microorganisms, microorganisms that metabolize nitrogen of organic compounds, cellulose-degrading microorganisms, and microscopic fungi depended more on the age of C. epigeios, and not on the stage of the succession of the studied area. The number of chemolithotrophic bacteria, particularly thiobacteria, decreased with the change of the growth phase of C. epigeios. The number of acidophobic thiobacteria depended more on the stage of succession, and the number of acidophilic thiobacteria depended more on the age of the C. epigeios. The number of microorganisms that metabolize nitrogen of organic compounds, oligonitrophilic microorganisms and microorganisms that metabolize nitrogen of inorganic compounds in the samples of tailings from the area with grasses and perennials and from the area with grasses, shrubs, and sun-loving trees was higher, compared to the number of these groups of microorganisms in the control and changed with the change in the growth phase of C. epigeios. The number of microorganisms that metabolize nitrogen of organic compounds, oligonitrophilic microrganisms and microorganisms that metabolize nitrogen of inorganic compounds was the highest in the samples from the area with grasses, shrubs, and sun-loving trees during the adult growth phase of C. epigeios. In the area where C. epigeios dominated within the vegetation, the highest number of microorganisms that metabolize nitrogen of organic compounds was also during the adult phase of C. epigeios, and the number of bacteria that assimilate mineral forms of nitrogen and oligonitrophilic microorganisms was the highest during the sub-adult stage. The index of pedotrophicity is higher in the samples taken in the area where C. epigeios prevails among other herbaceous plants, and where in the tree layer there are Betula pendula, Populus tremula with an admixture of Pinus sylvestris. Pedotrophicity indices which were calculated for these samples do not depend on the growth stage of C. epigeios and are higher than for the control area. Immobilization-mobilization of nitrogen indices in samples of tailings from the area with grasses and perennials and from the area with grasses, shrubs, and sun-loving trees ranged from 1.94 to 3.52 and were higher compared to the control site.

Soil and Vegetation Development on Coal-Waste Dump in Southern Poland.

As an anthropogenic element of urban landscapes, coal heaps undergo changes due to both natural and anthropogenic factors. The aim of this study was to determine the common development of soil under the influence of vegetation succession against a background of environmental conditions. Vegetation changes and soil properties were analysed along a transect passing through a heap representing a particular succession stage. It was found that changes in the development of vegetation were closely related to the stages of coal-waste disposal, where the initial, transitional, and terminal stages were distinguished. The mean range of pH (H2O) values in the profiles was 6.75 ± 0.21 (profile 1), 7.2 ± 0.31 (profile 2), 6.3 ± 1.22 (profile 3), and 5.38 ± 0.42 (profile 4). The organic carbon (OC) content in all samples was high, ranging from 9.6% to 41.6%. The highest content of total nitrogen (Nt) was found (1.132%) in the algal crust and sub-horizon of the organic horizon (Olfh-0.751%) and humus (A-0.884) horizon in profile 3 under the initial forest. Notable contents of available elements were found in the algal shell for P (1588 mg∙kg−1) and Mg (670 mg∙kg−1). Soil organic matter content was mainly dominated by n-alkanes (n-C11-n-C34) and alkanoic acids (C5–C20). Phytene and Phytadiene were typical for the algal crust on the initial pedigree. The initiation of succession was determined by the variation in grain size of the waste dumped on the heap and the variation in relief and associated habitat mosaic. Algal crusts forming on clay–dust mineral and organic material accumulating in the depressions of the site and at the foot of the heap can be regarded as the focus of pedogenesis.

Raman spectroscopy of anhydrous and hydrated aluminum sulfates: Experience from burning coal heaps

AbstractHydrated aluminum‐rich sulfates belong to less widespread secondary minerals on Mars, which are probably connected with hydrothermal alterations. On Earth, such sulfates result from acidic weathering of aluminosilicates, and their formation is controlled by factors such as pH, temperature, or water activity. Physical–chemical conditions can be reconstructed if specific sulfate phases are detected, and therefore, the investigation of sulfate assemblages in high‐temperature settings is important for planetology and exobiology research. Raman spectroscopy is a powerful analytical tool for the discrimination of sulfates, and the degree of hydration, which is a sensitive marker of temperature conditions, can be tracked using this method. However, spectral similarities of sulfates and metastability and rapid transformations may hinder their correct identification. We take advantage of in situ and laboratory Raman spectroscopy to characterize uncommon anhydrous and hydrated Al‐NH4 sulfate mineralogy which forms under elevated temperature at the Anna burning coal waste dump, Alsdorf, Germany, and can be considered as analogous to fumarolic environments. We detected a suite of hydrated Al sulfates (e.g. alunogen, khademite, and tschermigite) in the medium‐temperature zones (~50°C). To minimize possible rehydration processes, we deployed two miniaturized Raman spectrometers (532 and 1064 nm) for field investigations in the high‐temperature zone (~130°C to 150°C). Mixtures of anhydrous (godovikovite and millosevichite) and hydrated phases along with intermediate phases were detected in the field as well as in the laboratory. Such observations are consistent with the premise that the degree hydration of sulfates increase with decreasing temperature. These results confirm that Raman spectroscopy is, despite several analytical challenges, capable of distinguishing Al sulfates, and their hydration states, within complex aggregates and crusts, and future applications in planetary research are promising.

Influence of water erosion on fire hazards in a coal waste dump — A case study

Dump fires are a significant environmental problem in post-mining areas. The TEXMIN project has shown that climate change could lead to more extreme weather events in the future, intense precipitation among them. The impact of water erosion on the development of endogenous fires in coal waste heaps has not been investigated thus far. Meteorological data collected from the studied dump area in Libiąż, Poland confirmed that heavy rainfall occurred many times, causing surface erosion on the slope. Gully erosion was observed on the western slope of the heap, the depth of which was up to 1.6 m. Data showed that between areas with and without water erosion, there was a significant difference in measured temperatures and gas concentrations that defined the fire intensity. Erosion facilitated self-heating such that internal temperatures increased to 52.9 °C. Further, at a depth of 1 m in the self-heating zone, maximum gas concentrations were 15.65 vol%. CO2, 10 ppm CO, and 0.435 vol%. CH4, while the O2 concentration dropped below 1.0 vol%. These results show that despite preventative measures, thermal activity reactivated in the vicinity of gully erosion and caused the self-heating zone to expand.

High concentrations of HgS, MeHg and toxic gas emissions in thermally affected waste dumps from hard coal mining in Poland

This study aims to provide numerous environmental research approaches to understand the formation of mineral and organic mercury compounds in self-heating coal waste dumps of the Upper Silesian Coal Basin (USCB). The results are combined with environmental and health risk assessments. The mineralogy comprised accessory minerals in the fine fraction of thermally affected waste, i.e., Hg sulfides, most likely cinnabar or metacinnabar. Moreover, other metals, e.g., Pb, Zn and Cu, were found as sulfide forms. Apart from Hg, the ICP-ES/MS data confirmed the high content of Mn, Zn, Pb, Hg, Cr and Ba in these wastes. The high concentration of available Hg resulted in elevated MeHg concentrations in the dumps. There were no correlations or trends between MeHg concentrations and elemental Hg, TS, TOC, and pH. Furthermore, we did not detect microbial genes responsible for Hg methylation. The organic compounds identified in waste and emitted gases, such as organic acids, or free methyl radicals, common in such burn environments, could be responsible for the formation of MeHg. The concentration levels of gases, e.g., benzene, formaldehyde, NH3, emitted by the vents, reached or surpassed acceptable levels numerous times. The potential ecological and human health risks of these dumps were moderate to very high due to the significant influence of the high Hg concentrations.