Mine and Water

Mountainous areas have become among the most developed areas of geological hazards due to special geological environmental conditions and intensive human engineering activities. Geological hazards are a main threat to urbanization, rural revitalization, and new rural construction in complex mountainous areas. It is of great strategic significance to conduct large-scale geological hazard investigation and risk assessment in urban areas, control the risk of geological hazards at the source and propose risk control measures. In this paper, we established the technical methods of geologic hazard risk assessment and control in complex mountain towns by taking Longlin Town in the mountainous region of Gansu Longnan, China as the study area, with the Quanjia bay debris flows and Panping Village landslides as the typical pilot investigation and assessment. The methods consist of six stages—risk identification, hazard disaster model investigation, risk analysis, vulnerability assessment, risk evaluation and risk management and control measures and proposals. On this basis, the results of geological hazards with different precipitation frequencies (5%, 2%, 1%) are presented. The results show that 75.23% of the regions remained at low risk levels; 24.38% of the regions increased a risk level with decreasing precipitation frequency, and 0.39% of the regions remained at extremely high risk levels under different precipitation frequency conditions. For the Quanjia bay debris flows and Panping Village landslides case, we discussed the geological hazards risk source control contents, management and control technologies, engineering and non-engineering measures of disaster prevention and control for urban disasters and specific disaster areas. This research can provide technical support and reference for disaster prevention and mitigation, and territorial spatial planning. Full article

Mining has brought many environmental problems to the surrounding soil, water, and air, with toxic elements contaminating surface water, threatening ecological balance and human health. This study selected the Wenyu watershed downstream from a large molybdenum mine in the Qinling Mountains as the study area, aiming to explore the impact of molybdenum mining on surface water quality. The content characteristics of Cd, Pb, Cu, Cr and Hg in surface water, sediment, and rock samples were analyzed by field sampling and chemical testing. The results showed only obvious Cd pollution. The pollution status and ecological risk level of surface water and sediment samples in the Wenyu Stream watershed were evaluated using the single pollution index method, geo-accumulation index method, and Hakanson potential ecological risk assessment method. Finally, the sources of Cd pollution and the impact of mining on Cd distribution in the Wenyu Stream were comprehensively discussed. The research results showed that Cd content in the Wenyu Stream was significantly affected by mining activity and the coefficient of variation of Cd content reached 99.44%. Among 22 surface water samples, 21 samples met the Class II water standard, indicating a clean overall water quality of the Wenyu Stream, and only one sample exceeded the Class II water standard with a mild pollution level. All 15 sediment samples were polluted to varying degrees and the most severely polluted sample had reached a moderate to strong pollution level. Most of the samples were at a moderate pollution level. The potential ecological hazard indexes of Cd content were at medium to very strong risk level, indicating that the overall sediment in the main ditch of the Wenyu Stream was under a strong ecological risk level. The main sources of Cd pollution, including acid mine drainage, regional geological background, sediment release, and atmospheric dry and wet deposition, were discussed. Full article

As the second most significant metal following steel, aluminum plays a vital role in the advancement of both strategic emerging industries and national economic development. The existing oil and gas drilling data indicate that the deep bauxite deposits is abundant around the Ordos Basin in China, at the depths ranging from several hundred meters to several kilometers. Based on the geological and hydrogeological characteristics analysis, it is found that deep bauxite deposits in the basin have distinct electrical characteristics, characterized by four highs and two lows. While there is scarcity of prior research on the exploration topic for the technique limitation. In this paper, a logging interpretation model has been developed, which allows the evaluation of bauxite deposits. An efficient technology was proposed for deep bauxite exploration, utilizing an in-situ leaching mining technique. This technology is well-suited to the geological conditions of the Ordos Basin, ensuring that the solution flows within the bauxite ore bed without any seepage loss. To prevent the leaching solution from seeping into and polluting the main aquifer around the basin, several measures have been proposed. These include filling with polymer resin, well pattern seepage control plugging, and establishing monitoring systems. The results of this study provide a theoretical basis for the adoption of environmentally sustainable mining techniques and the mitigation of water pollution in deep bauxite exploration. Full article

Acid mine drainage (AMD) resulting from metal sulfide mining activities can lead to contamination by potentially toxic elements (PTEs) primarily concentrated around the mining area and gradually spreading outward. However, ecological risks do not correspond directly to PTE concentrations, making it challenging to effectively manage the mining environment and accurately prevent potential ecological impacts. In this paper, we analyzed Cd levels in sediments, soils, and corresponding rice grains sampled from four villages near Dabaoshan Mine of Guangdong, China, in 2017. Our results reveal that Cd is the most prominent pollutant element, exhibiting significant enrichment and spatial heterogeneity in both soil and sediments and higher accumulation levels in rice grains compared to other PTEs. Cd concentrations in soil decrease from the tailings pond to the river terrace, with a slight increase after Taiping River joins and flows into the alluvial plain. However, the concentrations in sediments show the opposite trend. The bioconcentration factor (BCF) for Cd in agricultural soil from the river terrace is lower than that from the alluvial plain and the degree of exceeding the maximum permit level (MPL) of Cd in rice grains increases along the river. Mineral transformation and topography are important factors in controlling the geochemical behavior of PTEs. Remediation efforts alter the physicochemical properties of the river, resulting in the release of PTEs during schwertmannite transformation followed by their adsorption by clay minerals. Furthermore, the random forest (RF) analysis highlights that the bioavailability and potential ecological risk of Cd in soils are governed by the occurrence form of Cd in different topographies, mainly controlled by TFe₂O₃, Mn, and CaO in the river terrace and CaO, Al₂O₃/SiO₂, and Mn in the alluvial plain. Therefore, considering the impact of topography on mineral compositions, physicochemical properties, and occurrence form of PTEs in soil and sediments is essential for assessing ecological risk in mining areas. Full article

Fluoride (F) is an essential element of drinking water for human health, especially for bone development and enamel creation. However, if the fluoride content in drinking water is higher than 1.5 mg/L or lower than 0.5 mg/L, it will cause endemic diseases, such as dental fluorosis. There are two main hydrogeological characteristics: the properties of the water-bearing rocks and groundwater conditions controlled the groundwater in guide basin. The geothermal water can be divided into fracture convection and sedimentary basin geothermal water according to its geological environment and heat transfer mode. Inductively coupled plasma spectrometry is a significant tool for groundwater quality analysis. The geochemical factors of fluoride enrichment in confined geothermal water mainly include pH, ion exchange, and mineral saturation. Both groundwater samples are slightly alkaline, while the phreatic water and surface water record pH values of 8.5, 7.78, and 7.8, respectively. The salinity of groundwater water is not high, but for confined geothermal water, phreatic water, and surface water measures 706.0, 430.1 and 285.9 mg/L respectively. The higher the pH of groundwater, the more beneficial it is to the enrichment of fluoride. In contrast, the main cations in phreatic water and surface water are calcium ions and magnesium ions. The anions in groundwater and surface water mainly include SO₄²⁻ and HCO₃⁻, followed by Cl⁻, indicating that the groundwater and surface water here is mainly leaching. Fluoride was shown to be positively correlated with sodium and bicarbonate. Moreover, the results indicate that F⁻ enrichment is usually associated with high HCO₃⁻ and Na⁺ concentrations in water, while a high Ca²⁺ concentration tends to lower the F⁻ concentration in water. This means that the ion exchange between calcium ions and sodium ions may lead to fluoride enrichment in natural water. As mentioned above, high-sodium and low-calcium water are favorable for fluoride enrichment. Moreover, saturation indices of fluorite, gypsum, dolomite, and calcite, as well as the saturation index of fluorite, represent a vital method to understand the fluoride enrichment. According to this study, fluoride as a pollutant poses great risks to human health overall, whether lower than or higher than the drinking water limit. Children face higher health risks than adults caused by confined geothermal water drinking intake. This study suggests that groundwater treatment should be conducted to reduce fluoride concentration in drinking water. It is suggested that when confined geothermal water is used as drinking water, it should be mixed with phreatic water and surface water in a certain proportion to make the fluoride in groundwater reach the range of safe drinking water. Full article

Mining of mineral resources exposes various minerals to oxidizing environments, especially sulfide minerals, which are decomposed by water after oxidation and make the water in the mine area acidic. Acid mine drainage (AMD) from mining can pollute surrounding rivers and lakes, causing serious ecological problems. Compared with traditional field surveys, unmanned aerial vehicle (UAV) technology has advantages in terms of real-time imagery, security, and image accuracy. UAV technology can compensate for the shortcomings of traditional technology in mine environmental surveys and effectively improve the implementat ion efficiency of the work. UAV technology has gradually become one of the important ways of mine environmental monitoring. In this study, a UAV aerial photography system equipped with a Red, Green, Blue (RGB) camera collected very-high-resolution images of the stone coal mining area in Ziyang County, northwest China, and classified the very-high-resolution images by support vector machine (SVM), random forest (RF), and U-Net methods, and detected the distribution of five types of land cover, including AMD, roof, water, vegetation, and bare land. Finally, the accuracy of the recognition results was evaluated based on the land-cover map using the confusion matrix. The recognition accuracy of AMD using the U-Net method is significantly better than that of SVM and RF traditional machine-learning methods. The results showed that a UAV aerial photography system equipped with an RGB camera and the depth neural network algorithm could be combined for the competent detection of mine environmental problems. Full article

The rational development of mineral resources provides necessary materials for economic development, but environmental pollution caused by mining activities is an inevitable consequence. Here, we present a case study of Chehe Town in Guangxi, an area with integrated metals mining and smelting. The geochemical distribution, migration, and transformation behaviors of Cd and other heavy metals were studied in detail by systematically collecting surface media such as atmospheric dust, surface water and stream sediments, ores, tailings, mine drainage, soil, and crops in and around the mining area. We used these data to explore the geochemical response of the surface environment to mining and smelting of metal sulfide deposits. The annual flux of Cd and other heavy metals near the mining and smelting sites was high. Due to the topography, heavy metals in the atmosphere are mainly transported via vertical deposition, influencing areas downwind for 25 km. The mine drainage exceeded As and Zn standards but had little impact on the surface water. The surface water quality was good, without acidification. Risks due to ore were much higher than that for tailings. Heavy metals buffered by surrounding carbonate rocks and secondary minerals mainly migrated as solid particles, resulting in the contamination of stream sediment by heavy metals. In mountainous areas, rivers are mainly affected by topography, flowing fast and dominated by downcutting, which caused heavy metal pollution in the sediment have a limited effect on the soil near the river. Heavy metal concentrations in the cultivated soil were greatly influenced by external input such as substantial atmospheric dust. However, only Cd accumulated in the crops, with very high concentrations in rice, but safe and edible levels in corn. Thus, in the mining area, the most sensitive to heavy metals was the atmospheric environment. High concentrations of heavy metals beyond the ore district are mainly concentrated in the sediment, with distant impacts. Therefore, it is necessary to monitor and control risks associated with sediment transport, conduct treatment, and adjust crop planting. The soil, river, and agriculture respond differently to mining activities, but the risk is low and can be managed as needed. Full article

South Africa is the home of major global mining operations, and the acid mine drainage (AMD) contribution has been attributed to abandoned mine sites and huge pyrite-bearing tailings from coal and gold mines. Determining the true economic impact and environmental liability of AMD remains difficult. Researchers have been looking into several treatment technologies over the years as a way to reduce its possible environmental impact. Different methods for active and passive remediation have been developed to treat AMD. The aim of this review was to describe the AMD-impacted environments and critically discuss the properties of AMD and current prediction and preventative methods and technologies available to treat AMD. Furthermore, this study critically analysed case studies in South Africa, gaps in AMD research, and the limitations and prospects offered by AMD. The study outlined future technological interventions aimed at a pattern shift in decreasing sludge volumes and operational costs while effectively improving the treatment of AMD. The various treatment technologies have beneficial results, but they also have related technical problems. To reduce the formation of AMD, it is recommended that more preventive methods be investigated. Moreover, there is a current need for integrated AMD treatment technologies that result in a well-rounded overall approach towards sustainability in AMD treatment. As a result, a sustainable AMD treatment strategy has been made possible due to water reuse and recovery valuable resources such sulphuric acid, rare earth elements, and metals. The cost of AMD treatment can be decreased with the use of recovered water and resources, which is essential for developing a sustainable AMD treatment process. More study is required in the future to improve the effectiveness of the various strategies used, with a focus on reducing the formation of secondary pollutants and recovery of valuable resources. Full article