Waste Rock Dump Research Articles

Geochemical characterization of waste rock dump and its potential to predict acid mine drainage

Acid Mine Drainage (AMD) is an environmental phenomenon that is being experienced by mining companies in Ghana. High levels of heavy metals have been reported in mining areas especially in Obuasi over the years; however, as to whether these heavy metals are being released from the mine wastes (waste rocks) is of concern. Therefore, this paper evaluates the potential of the abandoned Anyankyirem waste rock dump located in Obuasi to cause AMD. Twenty rock samples were collected from various locations of the dump site and their elemental and physicochemical compositions were examined. XRD analysis was conducted to assess the mineralogy of the samples. Acid Base Accounting (ABA) test was used to ascertain the AMD potential of the dump. The ABA test comprises calculating the Acid Neutralization Capacity (ANC) and Maximum Potential Acidity (MPA) of the various samples. The MPA and ANC values were used to compute the rock samples' Net Neutralization Potential (NNP). A column leaching test was carried out. Leachates were collected over a period of 20 weeks. From the column leaching experiment, the rate of weathering of calcium carbonate throughout the 20-week leaching experiment was 3.6 %. Leachates from the column test showed a circumneutral pH (7.1–8.0). The sulphate concentrations from the leachates decreased over the entire period from 96.60 to 3.70 mg/L. Iron recorded the highest concentration of 7783.65 mg kg-1 and the lowest of 0.645 mg kg-1 was recorded in Bi. From ABA test and the column leaching test results, Anyankyirem waste rock dump is not acid generating and therefore can serve as buffer for high pyrite waste rocks. However, significant levels of some heavy metals (As, Fe, Zn, Cr, Mn and Se) were recorded in the leachates even though the leachates’ pH were circumneutral. The results suggest that not only acidic conditions can leach out heavy metals.

The use of Groasis Waterboxx devices to improve mineland reclamation efforts by increasing transplant survival and growth of five native woody species

The reclamation of disturbed lands worldwide is a difficult and increasing problem. In the Mountain West region of the United States, mining activities commonly occur in zones dominated by native woody plants. The restoration of woody plants in these areas is challenging, and direct seeding efforts result in poor seedling emergence and establishment. Therefore, seedling transplants are often used, but they frequently experience high mortality during the first year, particularly due to summer stresses. We evaluated if the Groasis Waterboxx device could be used to mitigate drought stress on seedling transplants and improve their establishment on a reclaimed waste rock dump. The Waterboxx device collects precipitation into a polypropylene reservoir and slowly dispenses water onto the soil next to the seedling. To test such a hypothesis, 400 seedlings from five native woody plants (Atriplex canescens, Cercocarpus ledifolius, Pinus edulis, Purshia tridentata, and Rhus glabra) were planted with and without a Waterboxx. The Waterboxx device improved soil water potential, at 40 cm, it took 1 month longer to go below −1 MPa under a Waterboxx. Survival increased 30–65% in four of the five species, and seedling vigor increased for three of the five species. Vigor was higher with all plant species at both planting times and was significantly better in 50% of comparisons. Results support the use of the Waterboxx for improving seedling establishment on mineland overburden sites in the semiarid mountain west. The effectiveness of the Waterboxx device provides merit for future testing where drought challenges seedling establishment.

Prompt determination of predictive parameters for mining-technogenic landscape objects

The presented research is aimed at developing tools for quickly determining the geometric parameters of mining-technogenic landscape objects to solve various geotechnical and engineering problems, such as reclamation of lands disturbed by mining operations, as well as accumulated industrial waste utilization. The task of quickly determining the geometric parameters of the mining-technogenic landscape forms is proposed to be performed using the Blender software product for 3D-modeling and the Blender GIS Addon. The 3D models for mining-technogenic landscape objects have been constructed. In addition, the volumes of mined-out space at the granite quarry, the earth’s surface failure zone at the iron-ore mine and the mine waste rock dump have been determined. As a result, the values obtained were compared with actual data. It has been found that with the correct display of mining-technogenic landscape objects in the Google geospatial system, the proposed tools based on the Blender GIS Addon achieve high accuracy in determining parameters. The proposed method is predictive and cannot be independent, and it must be used in synthesis with surveying measurements of the parameters for mining-technogenic landscape objects and is a kind of a certain addition. However, it allows solving large-scale strategic problems in geoengineering.

Identifying sources of acid mine drainage and major hydrogeochemical processes in abandoned mine adits (Southeast Shaanxi, China).

Acid mine drainage (AMD) has resulted in significant risks to both human health and the environment of the Han River watershed. In this study, water and sediment samples from typical mine adits were selected to investigate the hydrogeochemical characteristics and assess the environmental impacts of AMD. The interactions between coexisting chemical factors, geochemical processes in the mine adit, and the causes of AMD formation are discussed based on statistical analysis, mineralogical analysis, and geochemical modeling. The results showed that the hydrochemical types of AMD consisted of SO4-Ca-Mg, SO4-Ca, and SO4-Mg, with low pH and extremely high concentrations of Fe and SO42-. The release behaviors of most heavy metals are controlled by the oxidation of sulfide minerals (mainly pyrite) and the dissolution/precipitation of secondary minerals. Along the AMD pathway in the adit, the species of Fe-hydroxy secondary minerals tend to initially increase and later decrease. The inverse model results indicated that (1) oxidative dissolution of sulfide minerals, (2) interconversion of Fe-hydroxy secondary minerals, (3) precipitation of gypsum, and (4) neutralization by calcite are the main geochemical reactions in the adit, and chlorite might be the major neutralizing mineral of AMD with calcite. Furthermore, there were two sources of AMD in abandoned mine adits: oxidation of pyrite within the adits and infiltration of AMD from the overlying waste rock dumps. The findings can provide deeper insight into hydrogeochemical processes and the formation of AMD contamination produced in abandoned mine adits under similar mining and hydrogeological conditions.

Needs and Options for Improving Gold Mining Waste Management Practices for Sustainable Development in Tanzania

The main objective of this study was to evaluate current mining waste management practices and their challenges. This study aimed to identify existing technologies and practices, and to present improvement needs and options for environmentally sustainable practices for mining operations. Other researchers have reported many practices and technologies for managing mining waste, but the efficiency, applicability, and need for customization were not specifically addressed for developing countries. This study used field observations, measurement methods, and laboratory analysis to collect data. This study showed a large amount of mine waste rock compared to the tailings wastewater from gold processing plant produced annually. This comprises approximately 5.2 million m3 of mine contaminated water generated by leaching from the waste rock dump (WRD) and 2.3 million m3 from the tailings storage facility (TSF). The study also identified the use of TSF cut-off trenches for seepage collection, the use of lime to treat acid mine drainage (AMD), the discharge of AMD into the TSF, and the recycling of TSF water as the best practices for managing mining waste. Furthermore, the study also found that the most common environmental problems were caused by TSF water and AMD water. However, mining waste management can be improved by modifying existing practices and adopting cost-effective technologies and practices to control and treat excess mining water.

MIGRATION OF HEAVY METALS FROM MINE WASTE ROCK DUMP END ENVIRONMENTAL IMPACT ON GROUNDWATERS AND SEDIMENTS

The environmental impact of mine waste rock dump, located in the region of Srednogorie, Bulgaria on groundwaters and sediments was studied. The acid mine drainage with low pH (2.43 - 3.53), high electrical conductivity (1500 - 4400 μS cm-1), content of Fe, Mn, Cu, Zn, Al, As and high concentration of sulfates (540 - 6905 mg L-1) are formed after heavy rainfall. The content of heavy metals, except manganese, in groundwater was significantly lower than that in the acid mine drainage, and the pH was in the range of 5.43 to 6.62. Sediments in the non-consequential vicinity of the mine waste rock dump had a pH in the range of 2.86 - 4.53 and contained heavy metals and As at concentrations higher than those in the mineral waste due to precipitation, co-precipitation and sorption reactions. An increase in the copper and zinc content in the exchangeable and organic matter fractions was found in the sediment sample. A relationship was found between arsenic and iron concentration in the sediments, which was mainly due to the retention of arsenic in the Fe and Mn oxides fraction. The concentration of total Mn in the sediments was lower than that in the mining waste due to the high mobility of manganese.

Use of solid mining waste to improve water retention capacity of loamy soils

Purpose. The research explores the possibility of increasing the fertile properties of agricultural soils of loamy type by adding burnt-out dump mass from coal enterprises. Methods. Laboratory research on parameters of penetration and retention capacity of sorbed and meniscal water for diffe-rent burnt-out rock fractions. The burnt-out rock was sampled from the mine No. 5/6 waste rock dump in the city of Myrnohrad, Donetsk Oblast, and divided into four fractions from 0.63 to 10 mm. The water penetration coefficient of the soil with the added dump mass is measured by the velocity of water seepage into the test samples. The ability of rock additives to retain film-sorbed and capillary water is assessed by comparing the weight of dry and moistened samples of crushed dump mass. Findings. The velocity parameters of water penetration into samples of loamy mixtures with burnt-out dump mass with fractions ranging from 10 to 0.63 mm in size have been determined. It has been found that an increase in the percentage of burnt-out rock in the mixture leads to an increase in the water penetration velocity from 1.2 ml/cm2·min with a rock content of 30% to 30.66 ml/cm2·min with a rock content of 70%. The highest penetration coefficients are achieved when adding rock with a small fractional composition of 0.63-3 mm, since an increase in grain size leads to a reduction in the coefficient by se-veral times. It has been determined that with an increase in the size of the rock fractions in a loamy mixture, the retention capacity of sorbed and pore water suitable for plant nutrition decreases by approximately 40%. Originality. For the first time, the parameters of penetration coefficients, as well as the accumulation of sorbed and meniscal water for mine waste in the Selidovo-Pokrovskyi district of Donbas, have been determined. Practical implications. The results obtained can be used to improve the physical properties of agricultural soils of loamy type by increasing their water retention capacity.

Chemical composition of arsenic-based acid mine drainage in the downstream of a gold mine: Fuzzy regression and clustering analysis

This study employs fuzzy regression and fuzzy multivariate clustering techniques to analyze arsenic-polluted water samples originating from acid rock drainage in waste rock dumps. The research focuses on understanding the complex relationships between variables associated with arsenic contamination, such as water arsenic concentration, pH levels, and soil characteristics. To this end, fuzzy regression models were developed to estimate the relationships between water arsenic concentration and independent variables, thus, incorporating the inherent uncertainties into the analysis. Furthermore, multivariate fuzzy k-means clustering analysis facilitated the identification of fuzzy-based clusters within the dataset, providing insights into spatial patterns and potential sources of arsenic pollution. The pairwise comparisons indicated the strongest correlation of 0.62 between soil total arsenic and pH, while the weakest correlation of 0.13 was observed between soil-soluble arsenic and soil iron, providing valuable insights into their relationships and impact on water arsenic levels. The associated uncertainties in the relationships among the variables were determined based on the degree of belongingness of each data point to various fuzzy sets. Three distinct clusters emerged from the analysis: Cluster 1 comprised Points 5, 6, and 7; Cluster 2 included Points 1, 2, 3, 4, 8, and 9; and Cluster 3 consisted of Points 10, 11, 12, and 13. The findings enhance our understanding of the factors influencing arsenic contamination to provide an effective mitigation strategy in acid rock drainage scenarios. This research also demonstrates the applicability and effectiveness of fuzzy regression and fuzzy multivariate clustering in the analysis of arsenic-polluted water samples.

Automated Detection and Analysis of Massive Mining Waste Deposits Using Sentinel-2 Satellite Imagery and Artificial Intelligence

This article presents a method to detect and segment mine waste deposits, specifically waste rock dumps and leaching wasted dumps, in Sentinel-2 satellite imagery using artificial intelligence. This challenging task has important implications for mining companies and regulators like the National Geology and Mining Service in Chile. Challenges include limited knowledge of mine waste deposit numbers, as well as logistical and technical difficulties in conducting inspections and surveying physical stability parameters. The proposed method combines YOLOv7 object detection with a vision transformer classifier to locate mine waste deposits, as well as a deep generative model for data augmentation to enhance detection and segmentation accuracy. The ViT classifier achieved 98% accuracy in differentiating five satellite imagery scene types, while the YOLOv7 model achieved an average precision of 81% for detection and 79% for segmentation of mine waste deposits. Finally, the model was used to calculate mine waste deposit areas, with an absolute error of 6.6% compared to Google Earth API results.

REHABILITATION OF MAN-MADE FORMATION OF ABANDONED COPPER PYRITE DEPOSITS ON THE EXAMPLE OF LEVIKHINSKY MINE (MIDDLE URALS)

Link for citation: Rybnikova L.S., Rybnikov P.A., Navolokina V.Y. Rehabilitation of man-made formation of abandoned copper pyrite deposits on the example of Levikhinsky mine (Middle Urals). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 137-150. In Rus. The relevance of the research is related to the need to rehabilitate of abandoned copper pyrite deposits affected by acid mine waters and justify measures to clean up the existing clarification pond. The main aim is to study the sludge composition and justify the measures to reduce the environmental load on the hydrosphere. Objects: clarification pond and neutralization sludge of the Levikhinsky copper pyrite mine acid mine waters. Methods. Laboratory studies of water and bottom sediments were carried out using atomic emission and mass spectral analysis; methods of flame emission spectrometry, flame atomic absorption, photometric method with Nessler's reagent, titrimetric, mercumetric and potentiometric methods; mass spectrometry with ionization in inductively coupled plasma and gravimetric method. Results. Sludge samples are dominated by sulfates (gypsum and bassanite), iron oxides and hydroxides (goethite), carbonates (calcite), clay minerals (mainly hydromica) and chlorine-containing salts (carnallite). The chemical composition of the sludge is dominated by oxides of iron, sulfur and calcium. The analysis of water and acid extracts showed that up to 24 elements belonging to hazard classes 2, 3 and 4 can be leached from the sludge in concentrations exceeding the maximum allowable values for fishery water bodies. Several options for the use of sludge from the clarification pond were analyzed: reclamation of waste rock dumps and substandard ores; backfilling of mined-out area of quarries; production of building materials; extraction of components; storage of sludge in geotubes (Geotube). The most rational is the disposal of sludge as the production of building materials on the basis of a public-private partnership, the implementation of which will allow the state and the private sector to derive mutual benefit.

Satellite-Based Mapping of Gold-Mining-Related Land-Cover Changes in the Magadan Region, Northeast Russia

Gold mining generates major environmental impacts like landscape degradation, accumulation of waste rock dumps, and water contamination by suspended solids. Russia ranks third in the world in gold production, but the impact of gold mining has not been previously estimated for its vast northeastern part. This study provides a detailed overview of land-cover changes associated with gold mining in the Magadan region (northeast Russia) in the 21st century, where alluvial gold production has increased by a third in the last 20 years. A long-term series of Landsat and Sentinel-2 images obtained in July and August are used to compile two datasets of mining-impacted areas with totally removed vegetation for 2000–2002 and 2022. We calculated the NDVI difference and then discriminated mining-related vegetation losses from other bare areas, using additional data like the classification of landforms based on the digital surface model and the data on mining allotments. The total area of gold-mining sites was estimated as 41,206 ha in 2000–2002 and 72,602 ha in 2022, with an increase of 26,031 ha over the past 4–6 years. Moreover, this is a lower-boundary estimate, without taking into account man-made reservoirs and historical mines recovered by vegetation. The spatial distribution of mining sites has not changed significantly over the past two decades and has a maximum in the western part of the region. We found that the floodplains of the Berelekh and Debin Rivers (large tributaries of the Kolyma River) are most heavily impacted by gold mining with a removed vegetation canopy occupying 16.0% and 11.2% of their area. Along with the land degradation assessment, we found that 19,900 ha of historical gold-mining sites in the Berelekh River basin are recovered by vegetation, which is comparable in size to the areas impacted by mining over the past 20 years.

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.

Passive removal of sulphate and heavy metals from acid mine drainage using sewage sludge and fly ash

This study aims to calculate the removal efficiency (%RE) of metals and sulphate and the constant rate of sulphate reduction from acid mine drainage (AMD) based on passive treatment principles named permeable reactive barrier (PRB) in batch test prior column test. Three media mixtures containing a variety of domestic sewage sludge (SE), mess hall compost (CO), cocopeat (CP), and fly ash (FA) were simulated. All reactive materials are solid waste from other operating units. M1 and M2 were contains organic and inorganic waste, M3 was only contain organic waste. The AMD was collected from a copper mining waste rock dump of which contained high sulphate, metals, and low pH. Batch tests were conducted in a series of glass bottles in an anaerobic chamber, and sub-samplings were taken on days 0, 7, 14, and 28. At the end of treatment, it indicated that M1 mixture resulting in the highest sulphate (SO4 2-) removal (44%), highest alkalinity generation of 1431 mg/L (as CaCO3) and %RE of Al, Cd, Co, Cu, Fe, and Zn were expected to be 100%, Ni 82%, Se 57%, and Mn 98%. Additional of FA for treatment such in M1 and M2 releasing more As in the final result compare to M3 that only contain organic substrates. The primary mechanism controlling the reaction from the M1 was a combination of sulphide precipitation enhanced by Sulphate Reducing Bacteria (SRB) activities supported by pH buffering and hydroxide precipitation. The sulphate reduction mechanism assumed to be the first-order reaction with highest rate constants found as 0.0208 d−1 from M1 reactors, 0.0144 d−1, 0.0161 d−1 for M2 and M3 respectively.

Geotechnical evaluation of a waste rock dump from a limestone mine in south Brazil

This paper presents the geotechnical study and stability assessment of a Mining Waste Rock Dump (WRD) from a Limestone Mine in the city of Dom Feliciano/Rio Grande do Sul (RS), south of Brazil. A literature review is used to provide considerations on the geotechnical properties of materials and geometries adopted. These parameters were the basis for the stability evaluation performed on realistic profiles of the WRD and on a proposed expansion. The conclusions regarding stability are confirmed and supported by a quantitative Waste Dump classification methodology. The results obtained demonstrate the viability of adopting an optimized geometry, with a height of 25 meters for the first level and 15 meters for the second level. It is concluded that the methodology and sequence of steps adopted in the evaluation can be replicated for other WRDs and even serve as an indication for similar structures.

Ecological hazard, typology, morphometry and quantity of waste dumps of coal mines in Ukraine

As a result of coal mining, a large number of waste rock dumps have been created on the earth's surface around the world. As a result of deflation and water erosion of the dump surface, extensive contamination of the soil cover of agricultural land with heavy metals occurs, threatening the food security of many countries. The article proposes a method for determining the area of potentially contaminated land in coal-mining regions. The area of such land in Ukraine has been estimated. A scheme for the dispersion of pollutants from waste dumps is proposed, which makes it possible to identify four types of polluted areas. Using the Google Earth service, the exact modern number of dumps in the Donetsk coal basin (Donbass) as a whole (1600) and separately in its western, central and eastern parts was determined. The average height, the average and total area of the base and surface, and the forest cover of the dumps in the Central Donbass were determined. It was found that the area of potentially contaminated land as a result of surface deflation of dumps in Central Donbass is 30,605 hectares. Taking into account the discharge of pollutants both from the surface of the dumps and from the deflationary pollution zone, the area of such land is 35,765 hectares. The mathematical modelling of the processes of pollutant removal by wind and deposition on the soil surface showed that it is possible to radically reduce the area of pollution by afforestation of waste dumps and, first of all, their flat tops.

Estimating Coal Mine Dump Stability from Its Natural Oscillations (Based on Seismic Monitoring at the Kolyvan Anthracite Deposit, Novosibirsk Region)

Abstract —Based on the analysis of the 2017–2021 recordings from the Kharino seismic station (the Altai-Sayan seismic stations network) and the 2002–2019 satellite imagery, the trigger of the July 18, 2020 earth-slide at Elbashinsky waste rock dump of the Kolyvan Anthracite Deposit (Novosibirsk region) has been established. The study of natural oscillations of the mine waste dump allowed estimating its stability and thus contributing to environmental and industrial safety in surface mining of solid minerals.

Global mining footprint mapped from high-resolution satellite imagery

Mining is of major economic, environmental and societal consequence, yet knowledge and understanding of its global footprint is still limited. Here, we produce a global mining land use dataset via remote sensing analysis of high-resolution, publicly available satellite imagery. The dataset comprises 74,548 polygons, covering ~66,000 km2 of features like waste rock dumps, pits, water ponds, tailings dams, heap leach pads and processing/milling infrastructure. Our polygons finely contour the edges of mine features and do not include the space between them. This distinguishes our dataset from others that employ broader definitions of mining lands. Hence, despite our database being the largest to date by number of polygons, comparisons show relatively lower global land use. Our database is made freely available to support future studies of global mining impacts. A series of spatial analyses are also presented that highlight global mine distribution patterns and broader environmental risks.

Influence of waste rock dump placement on the geomechanical state of underground mine workings

This paper is devoted to assessing the influence of waste rock surface dumps on the geomechanical state of underground mine workings. The conditions of the Pivdenno-Bilozerskyi high-grade iron ore field are chosen as the research object. To study the influence of dump placement and the depth of mine working on the mass stress state on the contour of sublevel drifts, a numerical modeling methodology based on the SolidWorks software package has been developed. This methodology involves the substantiation of the elements and properties of the geomechanical model, as well as the calculation scheme. Polynomial patterns of changing stress value in the hanging wall drift sides have been determined in the depth intervals of 440–740 m depending on the distance of the dump to the geometric center of the stope chamber. It has been revealed that the degree of the waste rock dump influence on the stress state gradually decreases with depth. It has been found that the maximum degree of the waste rock dump influence is observed on the upper horizons. When the waste rock dump is located above the geometric center of the future stope chamber that the stress value on the contour of the hanging wall drift can increase up to 10% compared to the absence of a dump on the earth’s surface. The research results are important for designing stable parameters for supporting sublevel drifts in difficult conditions of occurrence of the hanging wall rocks.

Assessment of seasonal changes in groundwater quality of waste rock dump in temperate continental climate, northern Japan

Understanding seasonal groundwater quality changes in temperate continental climate waste rock dumps (WRDs) is necessary for sustainable environmental risk prevention and legacy mine contamination management. Therefore, we conducted a field investigation of a WRD to determine the mechanisms controlling its groundwater quality dynamics. The research aimed to understand the impact of seasonal changes on heavy metals released from the WRD. Three monitoring wells were installed in the WRD to investigate the pH, electrical conductivity (EC), and groundwater level (GL). The mineral composition of the waste rock was determined. Groundwater and river water samples from the monitoring wells and rivers surrounding the WRD were collected for chemical analysis. The sphalerite and galena concentrated in the WRD were assumed to be the main sources of Zn, Pb, and Cd contamination. Summer rainfall was the dominant recharge source of river water, which rapidly infiltrated to the WRD, altering the pH, EC, and GL of the groundwater. The pH, EC, and GL were stable in winter because snowpack covering the surface soil prevented groundwater recharge to the WRD. However, snow melting affected the pH, EC, and GL in the WRD. The sources of groundwater recharge (rainfall, river water, and snowmelt) altered the behaviour of the heavy metals in the WRD through two main mechanisms: the dissolution of sulphide minerals and efflorescent salts upon contact with the recharge water, and the dilution effect of the recharge water, which mixes with the groundwater in the WRD, reducing the heavy metal concentration. Sulphide mineral and efflorescent salt dissolution were significant in the deepest monitoring well and rainfall was the dominant recharge source which increased sulphide mineral and efflorescent salt dissolution in the WRD.

Phytostabilization of coalmine overburden waste rock dump slopes: current status, challenges, and perspectives

Phytostabilization of coalmine overburden waste rock dump slopes: current status, challenges, and perspectives