The German government's decision to phase out lignite mining by 2038 or earlier, as recently 2030 has been agreed for the Rhineland, will trigger a number of transition processes in Germany's remaining lignite mining areas. The two largest lignite mining areas are located in geographically different regions: Rhineland in the west and Lusatia in the east. As the socio-economic and environmental conditions in these two mining areas are set to change dramatically, the German government has adopted extensive economic support measures. However, the environmental changes will also lead to changes in the ecosystem functions and services provided by the future post-mining landscapes.

Gerwin et al. (2023) compare the two main lignite producing regions of Germany in terms of their natural and cultural environments. The economic situation and its history are reflected and differences are outlined. Part of the differences in cultural development can be explained by the natural conditions, especially the edaphic factors and the climatic situation. Because of the specific geological settings, tailored mining technologies were developed and used in the two regions, with different effects on the resulting post-mining landscapes.

We conclude that the landscapes of Lusatia and the Rhineland have been radically restructured by the long and varied history of lignite mining. Both regions will change significantly as the mining industry continues to decline and is expected to cease altogether within the next decade. These changes in the post-mining landscapes and the ecosystem services will provide both challenges and opportunities. The preconditions for positive socio-economic development and for sustainable land use concepts that also consider ecological aspects are different for the two regions. The exchange of knowledge and experience between the two mining regions is crucial to the success of this major transformation process, despite, or perhaps because of, these differences.

Gerwin, W., Raab, T., Birkhofer, K., Hinz, C., Letmathe, P., Leuchner, M., Roß-Nickoll, M., Rüde, T., Trachte, K., Wätzold, F., Lehmkuhl, F. (2023): Perspectives of lignite post-mining landscapes under changing environmental conditions: what can we learn from a comparison between the Rhenish and Lusatian region in Germany? Environmental Sciences Europe 35:36. https://doi.org/10.1186/s12302-023-00738-z

How to cite: Lehmkuhl, F., Gerwin, W., Raab, T., Birkhofer, K., Hinz, C., Letmathe, P., Leuchner, M., Roß-Nickoll, M., Rüde, T. R., Trachte, K., and Wätzold, F.: Perspectives for the lignite post-mining landscapes of the lignite mining landscapes under changing environmental conditions – what can we learn from a comparison between the Rhenish and the Lusatian regions in Germany?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2791, https://doi.org/10.5194/egusphere-egu24-2791, 2024.

In this study, we report lead isotopic compositions from oxidized Cu ores, host rocks, metal smelting residues, and soils from the Zechstein Ca1 formation which is associated with the Kupferschiefer copper deposits. The lithology is dominated by marls and slates, where Cu mineralization appears in carbonates, mostly malachite. Historical smelting left numerous slag remnants around the site (Derkowska et al. 2023). The Pb isotope ratios in ores and slags are highly diverse in comparison to previous studies of Cu ores and smelting products in Poland (Tyszka et al. 2012), i.e. ²⁰⁶Pb/²⁰⁷Pb ratio ranges from 1.094 to 2.092 for ores and from 1.151 to 1.240 for slags. This diversity is likely related to the oxidized character of the ore, which contains less Pb compared to sulfide-dominated ores and, in consequence, its Pb isotopic composition is dominated by radiogenic Pb produced by U-rich host rocks. This translates to significant differences in Pb isotope records between oxidized and reduced (sulfide) deposits that can be utilized in environmental and provenance studies. Similar diversity in soil samples is consistent with contamination by such ores and/or slags. Analyzed soils show highly variable ²⁰⁶Pb/²⁰⁷Pb ratios in lower soil horizons, whereas Pb isotope ratios in topsoils are similar to those typical for a whole region of Lower Silesia in Poland (1.17-1.19). This suggests the dominance of modern atmospheric Pb in the surface environment which we link to Polish and Czech coal combustion and name as the Lower Silesian Contemporary Pollution Signal.

Our study shows that using oxidized Cu-ores may introduce high diversity in Pb isotopic composition to smelting products, wastes, and consequently the environment. This affects both environmental and provenance studies as only a restricted isotope ratio can be attributed to a single source. On the other hand, high diversity in ²⁰⁶Pb/²⁰⁷Pb ratios in slag samples may also indicate the addition of oxidized Cu ores during smelting thus may be also an asset to identify when oxidized ores were used or acted as a pollution source.

Acknowledgments: The study is funded by the National Science Centre grant to KD (2019/35/N/ST10/04524)

Derkowska K., Kierczak J., Potysz A., Pietranik A., Pędziwiatr A., Ettler V., Mihaljevič M., 2023, Combined approach for assessing metal(loid)s mobility and accumulation in a near-neutral (pH) environment of a former Cu-smelting area in the Old Copper Basin, Poland: when nature is the ‘bad guy’. Applied Geochemistry, 105670. https://doi.org/10.1016/j.apgeochem.2023.105670

Tyszka R., Pietranik A., Kierczak J., Ettler V., Mihaljevič M., Weber J., 2012, Anthropogenic and lithogenic sources of lead in Lower Silesia (Southwest Poland): an isotopic study of soils, basement rocks and anthropogenic materials. Applied Geochemistry, 27, 1089-1100, http://dx.doi.org/10.1016/j.apgeochem.2012.02.034

How to cite: Pietranik, A., Derkowska, K., Kierczak, J., Ettler, V., and Mihaljevič, M.: Lead isotopic composition of the oxidized Cu ores, slags and soils from the Old Copper Basin, Poland and its implications for metal-provenance and environmental research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11829, https://doi.org/10.5194/egusphere-egu24-11829, 2024.

Challenge 

While recycling and alternative technologies show promise in reducing reliance on primary raw materials, the direct acquisition of essential metals and minerals depends on extracting new resources. The increasing demand for these resources has significant implications for mining, mineral processing, and environmental impact. Failing to effectively manage this demand for raw materials and mitigate the environmental impact of mining could impede global progress towards a cleaner energy future. The M4Mining project aims to promote sustainable mining practices using integrated remote sensing data to help monitor these operations. Its primary objective is to develop comprehensive remote sensing solutions for mining and tailings sites. This abstract introduces the identification of secondary iron minerals as proxies for estimating possible acid mine drainage (AMD) occurrence in legacy mine sites in both Cyprus and Australia.

Methodology 

Hyperspectral data of the secondary iron minerals hematite, goethite, limonite (goethite + lepidocrocite), jarosite and copiapite were collected in a laboratory setting to develop a method to separate secondary iron minerals from other minerals. Filtering by threshold of various indices, NDVI, ferric iron index, and iron feature band ratio, were best suited for this purpose. After filtering, the remaining pixels of the secondary iron minerals were predicted using a random forest (RF) classifier-model. It was possible to distinguish between the mineral classes hematite, goethite/ lepidocrocite and jarosite with over 93% area adjusted overall accuracy using 30 random control pixels for both sensors.

Results 

The first case study is applied is the Cu-Au-Pyrite mine Skouriotissa in the Republic of Cyprus. A spectral resampling from the hyperspectral laboratory data to Sentinel-2 (S2) and WorldView-3 (WV3) spectral resolution made it possible to adjust the hyperspectral method and provide results for both satellite sensors. Comparing the resulting maps show differences of minerals mapped on the surface likely due to the sensor’s different spatial resolution (S2 20m vs WV3 3.7m pixel). 

The M4Mining partners completed their first field survey in North-Western Queensland at the Mary Kathleen legacy mine site in September 2023. The former Uranium (U) open pit mine was active until 1982 and rehabilitated in 1985. The area was surveyed via UAV-borne hyperspectral data collection and satellite-borne hyperspectral (EnMap) instruments to assess the site's rehabilitation status. The method tested in the Republic of Cyprus is being applied to the Mary Kathleen site to evaluate surface oxidation processes that could indicate acid pH environments. A special focus is set on the gradient between the capped evaporation pond and the surrounding environment including the discharge area from the former pond. Different standard hyperspectral and multispectral algorithms are used to map the spatial distribution of iron oxides and evaporates. Although a final evaluation of the rehabilitation of the area is outside the scope of this study, the data collected intend to add valuable information to the continued monitoring of the site. 

Preliminary results from Australia will be provided for relative surface changes as indicators for processes occuring under the capped evaporation pond.

How to cite: Hildebrand, J. C., Koerting, F. M., Savinova, E., Micklethwaite, S., Erskine, P. D., Lindblom, D., Greenwood, M., Brown, D., and Koellner, N.: Satellite and UAV monitoring of legacy mine sites via secondary iron mineral proxies. Case studies from the Republic of Cyprus and Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12399, https://doi.org/10.5194/egusphere-egu24-12399, 2024.

Worldwide uranium production is based on the In Situ Recovery mining technique. This exploitation mode directly falls within the scope of the applications of reactive transport modelling to optimize uranium production and limit its associated environmental impact. We hereby propose a modelling approach which is able to represent the natural evolution of the aquifer impacted by the exploitation of an ISR test. Model is calibrated on 12 year-long data obtained from 12 monitoring wells surrounding the ISR pilot cell. Through this process based approach, we simulate the impact of several remediation strategies which could be considered in these contexts. In particular, we model the impact of pump and treat combined with reverse osmosis as well as the circulation of non-impacted fluids through the reservoir with different operating strategies. We show that our approach allows to compare the effectiveness of these strategies. We show that, for this small-scale ISR pilot, monitored natural attenuation constitutes an interesting approach due to its faster pH recovery time with respect to Pump & Treat and circulation of unimpacted fluids. Combined with an economical evaluation of their deployment, this approach can help the mining operator select and design the optimal remediation strategies, from an environmental and economical standpoint.

How to cite: Seigneur, N., Grozeva, N., Purevsan, B., and Descostes, M.: Reactive transport modelling as a toolbox to compare remediation strategies of aquifers impacted by uranium in situ recovery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18871, https://doi.org/10.5194/egusphere-egu24-18871, 2024.

Worldwide, In situ recovery (ISR) is the most widely used uranium mining technique. As of 2022, it accounted for 55% of global uranium production. Uranium ISR consists in dissolving the ore minerals using an acidic leaching solution directly within the deposit through a series of injection and extraction wells. The U-enriched solution is then pumped to the surface in order to separate the dissolved uranium from the acid solution. Reagents are then recycled before being reinjected into the deposit. The key advantage of ISR over conventional underground and open-pit mining lies in its significantly

reduced costs and environmental footprint since it generates no tailings or solid waste and does not require excavation of the rock. It is by far the most cost effective extraction technique. However, an ISR exploitation impacts the groundwater quality by increasing the concentration of dissolved elements (SO4, ...) and decreasing the pH. Subsequently, groundwater impacted by acid ISR mining is typically remediated using various rehabilitation strategies.

This study aims to forecast uranium production and predict the long-term environmental footprint of such exploitation using a reactive transport modeling approach. To do so, we will use HYTEC,  an  investigative tool to assess both production and the environmental footprint of an ISR mining site. HYTEC includes the three-dimensional hydrogeochemical simulation of the relevant chemical reactions which govern uranium production and the long-term evolution of the aquifer. The model is applied to an uranium deposit of the KATCO mine in Kazakhstan that has not been exploited yet. This model can simulate the 3D evolution of the aquifer geochemistry during and after the production phase.

We will study how operating parameters (well design, injection-production rates, acidity and oxidation levels, …) impact both the uranium production and the environmental footprint of the ISR exploitation. The environmental footprint can be described in terms of distance and time. The distance is generally controlled by the migration of sulfate ions resulting from the injection of sulfuric acid, which have low reactivity and hence an important mobility. Acidity or pH is the parameter which influences the duration of the impact, as H⁺ has a very important reactivity and can also be stored locally by adsorption on clay mineral surfaces. The geochemical model, previously developed in a separate study, suggests that cationic sorption on clay surfaces and the precipitation of secondary minerals like gypsum regulate the behavior of contaminants (SO₄, pH) over extended durations and distances.

How to cite: Doucmak, R., Seigneur, N., Escario, S., Lagneau, V., and Descostes, M.: Multi-criteria optimization of uranium exploitation by In Situ Recovery , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19363, https://doi.org/10.5194/egusphere-egu24-19363, 2024.

Preventing coal spontaneous combustion fire by using inhibitor is an effective control measure. The oxidized spontaneous combustion characteristics of coal can reflect the performance of coal, and a suitable structural model can reflect the performance of coal more intuitively, and can also lay the foundation for the study of the action mechanism of the inhibitor. In this study, samples from Baishihu coal mine were selected, and diethylenetriaminepenta-methylenephosphonic acid (DTPMP) was used as a blocking agent to investigate the macromolecular structure, microcrystalline structure changes and oxidation process of coal by X-ray photoelectron spectroscopy (XPS), carbon nuclear magnetic resonance (¹³C-NMR), and Fourier infrared spectroscopy (FTIR). The molecular formula C₁₉₈H₁₆₄O₄₀N₂ and the molecular structure model were obtained. ChemDraw and Materials Studio were used for the experimental data, and high-resolution transmission electron microscopy (HRTEM) was used to verify the aromatic ring structure built to make the constructed structural model more accurate. In the water evaporation stage, the high ring aromatic layer is converted into the low ring number. Furthermore, in the high-temperature stage, the low ring aromatic layer is transformed due to the coking and condensation reaction of the coal sample. With the increase in the treatment temperature, water loss is heavier, oxygen absorption and weight gain are perplexing, and the value of the burnout temperature is higher. The elemental composition of the coal samples was changed after the addition of the hindering agent, and the temperature at which small free radical molecules were produced and the time at which gaseous products appeared during the coal-oxygen reaction were delayed. The characteristic temperature increases with the increase of the resist concentration and the activation energy decreases in the water evaporation stage and increases in the other two stages. The apparent activation energy of the coal-oxygen reaction increases and the reaction becomes more hard and complex to realize. DTPMP mainly reacts with free radicals and reactive oxides and forms an adsorption layer on the coal surface. And the molecular structure of the inhibitor contains several phosphate functional groups, which can react with the oxides in the coal to form phosphate substances and fill the pores in the coal. It can reduce the evaporation of water and the contact of coal samples with oxygen. These mechanisms interact with each other and together reduce the reactivity of the coal and the risk of spontaneous combustion. This study furthers the understanding of coal spontaneous combustion in this mining area, provides a reference for the prevention and control of coal spontaneous combustion.

How to cite: Zhang, W. and Zeng, Q.: Study on the Effect of DTPMP Inhibitor on Oxidation and Structural Characteristics of Coal Spontaneous Combustion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4496, https://doi.org/10.5194/egusphere-egu24-4496, 2024.

The demand for environmentally friendly materials in our habitat is a major challenge. Alkali activation, such as in geopolymers, offers a potential solution for waste valorization, providing an alternative to cement-based materials and contributing to the circular economy.

This study explores the use of mine waste from an abandoned Pb-Zn site in Northern Tunisia as an inexpensive and high adsorption capacity additive in the synthesis of geopolymers. The mine waste was used to replace metakaolin in the geopolymer formulations to minimize the environmental impact. Two types of metakaolin (commercial 1200S MK, AGS Mineraux, France and Portuguese Vicente Pereira, VPMK) were used in the formulations. Microstucture, mechanical properties, and Methylene Blue dye adsorption were studied.

Results revealed alarming concentration of potentially toxic elements in the mine waste (28.040 mg kg⁻¹ Pb and 94.420 mg kg⁻¹ Zn), presenting an environmental hazard and pointing up the need to stabilize these materials in order to prevent leaching.  Mechanical behaviour at 28 days of curing was promising (up to 32MPa) in the case of the VP based metakaolin formulations. The microstructure, studied by SEM, is consisted of voids, macro and meso pores, giving the geopolymers a high adsorption capacity. The synthetized geopolymers were utilized for the adsorption of methylene blue (MB) by investigating the effect of the amount of the adsorbent and the shaking period. The batch kinetics study fitted best into the pseudo second order reaction kinetic model. In isotherm modelling studies, the Langmuir isotherm model was best fitted and was used to describe the mechanism of the adsorption. Samples with 40 wt.% VPMK and 100 wt.% MK showed the best adsorption capacity revealing the effect of the waste in the amelioration of the alkali-activated metakaolin based geopolymers and its potential in the restitution of metakolin.

How to cite: Nouairi, J., Andrejkovičová, S., Karoui, O., Pinho, T., Rebelo, R., Rocha, F., and Ghribi, M.: Towards Sustainable Mining: Geopolymer Formulations for Eco-Friendly Mine Waste Management and Recycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20556, https://doi.org/10.5194/egusphere-egu24-20556, 2024.

Mining activity has been an essential human activity since ancient times, contributing to human society's economic and cultural development. Today, surface mining activity in Greece is significant both economically and socially. A large number of quarries for aggregates and ornamental stones throughout the country contributes to the economic development of local communities and is the main occupations of mineral resources engineers.

However, it is an activity that significantly affects the natural environment, causing a range of impacts, reversible or irreversible, leading to the degradation of the area and visual alteration of the landscape. The environmental impact is considerable, and the concerns about protecting the landscape and ecosystems are growing. All thesecan be anticipated and dealt with by organizing and planning a landscape restoration study.

This research focuses on the landscaping and restoration of an aggregate quarry at the 'Latzimas' site in the prefecture of Rethymnon, Crete. In this context, two restoration proposals are made, including:

- the phytotechnical restoration of the quarry benches and pit floor using appropriate plant species,

- and the reuse of the quarry through the creation of a:

• A) model vineyard,
• B) botanical garden.

Usually, as the most suitable vegetation species are chosen the ones that thrive in the area instead of the ones that thrive in poor nutrient conditions, such as the environment of the abandoned quarries. Because of the above, the quarry engineer, who usually does not have the necessary knowledge of botany, will need to consult with experts (e.g. botanists and foresters) to ensure that the restoration plan is effective and not only aimed at meeting the obligations imposed by the legislation.

How to cite: Xiroudakis, G., Saratsis, G., Gogali, K., and Giannakaki, M.: Abandoned quarry reclamation by selecting the appropriate plant species., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1413, https://doi.org/10.5194/egusphere-egu24-1413, 2024.

In the Czech part of the Upper Silesian Coal Basin (USCB), there are several places of coal wastes storage. Within improperly protected heaps, the self-heating and spontaneous burning processes may develop, resulting in the emission of gaseous, water-soluble and solid (tars, dust) pollutants.

The thermal processes have developed within the heap in Hermanice (Ostrava) since the 1990s. Recently, the most thermally active is the eastern part of the deposit. The purpose of the study was to evaluate the progression of the fire based on temperature measurements, molecular and stable isotope composition of gases emitted from thermally active parts of the deposit. The sampling was conducted in the same places in January, April and September 2023. One of the sampled points was a steel pipe that penetrated the dump to a depth of ca. 12 m, where, according to Diamo Ltd., it was ca. 350 °C. The other 3 sampling points were located in areas of visible thermal activity (steam or smoke emissions). Surface temperature measurements in these spots ranged from 3 to 345 °C, and at the probe depths (50-100 cm), from 66 to 363 °C. Gases were taken at each point twice: directly from the chimney where the outflow of gas/vapour was visible (sample SURF) and after sticking the probe into the ground (sample DEEP).

During the study period, in the zone of intense thermal processes (southeastern part of the heap), large changes in temperature and gas concentrations (N₂, O₂, hydrocarbons (HC), CO, CO₂, H₂ and S-compounds) were noted. In general, SURF gases were found to be richer in pollutants than DEEP gases. This suggests that the gases coming to the surface flow from much deeper parts of the heap than those reached with the sampling probe. The highest concentrations of CO₂ (19.17%), CO (0.67%), HC (2.43%), H₂ (6.26%) and S-compounds (844 ppm) were found in April in gas coming out of the pipe (from the highest temperature, ca. 350^oC). In September, the zone with the highest temperatures shifted to the north, and the concentrations of monitored gases generally decreased, indicating material burnout in the hot spot. The δ¹³C(CH₄), δ²H(CH₄), and δ¹³C(CO₂) values indicate the thermogenic origin of all gases.

At a point ca. 100m away from the hot spot, temperatures of ca. 65-75^oC were found during all measurements, and the gas composition was independent of the sampling depth. The highest concentrations of CO₂ (20.21%), HC (3.30%) and H₂ (0.5%) were found during the April campaign. The isotopic composition of selected gases suggests their relation to low-temperature thermogenic processes; the presence of a component of microbial origin is not excluded.

The data presented here show that the molecular and isotopic composition analysis of gases is a good tool for tracking processes in thermally active coal waste dumps.

This study was financed by the AGH University of Krakow as a part of the programme Excellence Initiative – Research University, Action 4, Grant No. 4113.

How to cite: Więcław, D., Jurek, K. J., Geršlová, E., Kowalski, T., and Bilkiewicz, E.: Fire progression within coal waste heap in Heřmanice, Upper Silesia, Czech Republic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14890, https://doi.org/10.5194/egusphere-egu24-14890, 2024.