Semi-arid Mining Areas Research Articles

Response of ecosystem services and environmental dynamics in large open-pit coal mines: A case study in semi-arid areas

Surface coal mining in semi-arid regions has detrimental impacts on the structure and function of surface ecosystems, thereby impeding the attainment of regional sustainable development goals. Moreover, the impact of climate change on ecological restoration in semi-arid mining areas is an inevitable consideration. To elucidate the response of ecosystem services in mining areas to regional climate change, topography, soil, vegetation and socioeconomic development, this study selected six large-scale surface coal mines located in semi-arid regions of China as research objects. In this study, we aimed to assess the main ecosystem services (carbon sequestration, soil conservation, and flow regulation) provided by these mines. In addition, we analysed the spatial and temporal evolution and interrelationships of these ecosystem services. Furthermore, we explored the underlying mechanisms between ecosystem services and environmental factors. The results showed the following: (1) Geospatially, there was a gradual decrease in carbon sequestration and flow regulation from northeast to southwest in the mining areas. However, the soil conservation exhibited an upward trend. Throughout the research period, the carbon sequestration change rate in the six mining areas displayed an initial downward and subsequent upward trend, the rate of soil conservation exhibited a gradual upward trend, and the flow regulation decline rate followed a downward trend. (2) Change rate of carbon sequestration and soil conservation in the six mining areas showed a significant positive correlation (r = 0.51, p < 0.001), with the strongest correlation observed in the Shengli Mining Area (r = 0.64, p < 0.001). (3) Ecosystem service changes in the mining areas were primarily driven by initial conditions (95.0%), followed by meteorological factors (4.2%). Three ecological restoration models were proposed for the different regions based on driver analyses. The findings of this study offer scientific evidence that can be used to inform ecological management, enhance ecological security, and promote regional sustainable development in mining areas.

Species Diversity and Soil Interconstraints Exert Significant Influences on Plant Survival during Ecological Restoration in Semi-Arid Mining Areas

The extensive vegetation destruction in opencast mining regions has led to various environmental problems, including the loss of biodiversity. However, our understanding of biodiversity’s response to survival, as well as its interactions with soil characteristics and climate change, remains limited. To address this gap, we analyzed data from a long-term monitoring site in an opencast coal mine reclamation region, focusing on the effects of species diversity, soil properties, and climate factors on the survival of four key restored species at 17, 22, and 27 years after planting. Our findings indicate that increased plot diversity is associated with decreased overall survival, and significant variations in diversity levels were observed among different plots. We also found that soil properties influenced species’ survival response to diversity, and these responses varied with stand age. In the early stages of succession, soil and diversity primarily affect species survival, with diversity playing a more dominant role as stand age increases. Overall, our findings suggest that the interaction between species diversity and soil composition significantly influences the survival of species. Continuous monitoring is necessary to validate these conclusions, particularly considering the diverse planting patterns in mine reclamation areas that can result in varying feedbacks of biodiversity on species survival.

Arbuscular mycorrhizal inoculation alleviates water competition between adjacent plants in the mixed planting system

Exploring the water use strategies of different plant species is very important in understanding the mechanisms of soil-plant interactions in water-limited ecosystems. There is limited information on changes in plant water use in mixtures of species, and little is known of the role of arbuscular mycorrhizal fungi in regulating the water use strategies of host plants in mixtures. The water use strategies of three plant communities in arid and semi-arid mining areas were investigated. These were Medicago sativa (alfalfa) in monoculture (A), Caragana korshinskii (Korshinsk pea shrub) in monoculture (C), and Medicago sativa + Caragana korshinskii in mixture (MIX). Each plant community was inoculated with an arbuscular mycorrhizal fungus or uninoculated to determine the regulation of plant water use strategy by the fungus. There was a significant difference in the use of soil water by both plant species in mixture compared with monoculture (P < 0.05). In the mixture there was significant competition for water between depths 0–40 cm and 40–100 cm. Both species took up more water from the surface soil than in monoculture. Mycorrhizal inoculation reduced the dependence of the plants on surface soil water, effectively alleviated the competition for water between the two plant species in mixture. The results indicate that the impact of arbuscular mycorrhizal fungi on the water use strategies of different plant species in mixtures should be considered when ecological restoration of vegetation is carried out in arid and semi-arid areas.

Study on dynamic adsorption characteristics of gangue to heavy metals in goaf and its water purification mechanism under leaching condition

Arid and semi-arid mining areas in Western China are faced with the problems of water shortage, large water inflow of mines and high-salinity of mine water. When the broken gangue is backfilled to the goaf by the solid backfilling mining technology, a large number of voids between the blocks is generated, which can store groundwater and purify water quality. In this study, the real void structure of the gangue backfilling body in the goaf was obtained through CT scanning. By using the COMSOL numerical simulation software, a coupling model of Free and Porous Media Flow and Transport of Diluted Species in Porous Media was established. From the mesoscopic void scale, the effects of particle size distribution, inflow velocity and ion concentration on the flow field characteristics, ion migration and dynamic adsorption characteristics of gangue in the leaching column were explored, and the purification mechanism of broken gangue to heavy metals in mine water was revealed. The results show that: (1) The larger the gangue particle size gradation, the larger the void size, the higher the velocity in the void, and the more significant the average flow velocity difference between the void area and the gangue area. With the increase of inflow velocity, the average velocity in the gangue area and void area also increases, but the average flow velocity in the void area is 5.36 times that in the gangue area; (2) Both the larger particle size gradation of gangue, higher inflow velocity and inlet concentration can improve the velocity of the ion migration in gangue leaching column; (3) The greater the inlet concentration, the faster the flow velocity, the higher the total adsorption rate of gangue in the leaching column; (4) Both decreasing the particle size gradation of the gangue and increasing the inlet concentration can increase the total adsorption capacity of gangue in the leaching column; (5) The removal of heavy metals by gangue is the result of physical adsorption, ion exchange and other reactions. The research results can provide theoretical reference and data support for the treatment of high-salinity mine water in mining areas of Western China.

Multispectral Remote Sensing Monitoring of Soil Particle-Size Distribution in Arid and Semi-Arid Mining Areas in the Middle and Upper Reaches of the Yellow River Basin: A Case Study of Wuhai City, Inner Mongolia Autonomous Region

Particle size distribution is an important characteristic of reclaimed soil in arid and semi-arid mining areas in western China, which is important in the ecological environment protection and control of the Yellow River Basin. Large-scale coal resource mining disturbances have caused serious damage to the fragile ecological environment. The timely and accurate dynamic monitoring of mining area topsoil information has practical significance for ecological restoration and management evaluation. Investigating Wuhai City in the Inner Mongolia Autonomous Region of China, this study uses Landsat8 OLI multispectral images and measured soil sample particle size data to analyze soil spectral characteristics and establish a particle size content prediction model to retrieve the particle size distribution in the study area. The experimental results and analysis demonstrate that: (1) the 6SV (Second Simulation of the Satellite Signal in the Solar Spectrum Vector version) atmospheric correction model is more accurate than the FLAASH (Fast Line-of-sight Atmospheric Analysis of Hypercubes) model in arid and semi-arid areas with undulating terrain; (2) 0–40 cm is the optimum soil thickness for modeling and predicting particle size content in this study; and (3) the multi-band prediction model is more precise than the single-band prediction model. The multi-band model’s sequence of advantages and disadvantages is SVM (Support Vector Machine) &gt; MLR (Multiple Linear Regression) &gt; PLSR (Partial Least Squares Regression). Among them, the 6SV-SVM model has the highest precision, and the prediction precision R2 of the 3 particle sizes’ contents is above 0.95, which can effectively predict the soil particle-size distribution and provide effective data to support topsoil quality change monitoring in the mine land reclamation area.

Migration, accumulation, and risk assessment of potentially toxic elements in soil-plant (shrub and herbage) systems at typical polymetallic mines in Northwest China.

In grassland systems of the semi-arid mining area, the migration, accumulation, and bioavailability of potentially toxic elements (PTEs) are important ecological and health risk issues. Thirty-eight pairs of topsoil (0-20 cm) and plant samples were collected around Baiyin City and in Dongdagou stream valley to investigate the migration of PTEs in soils, transfer of PTEs in soil-plant (shrub and herbage) systems, and assess the risk in soils and plants. The total concentrations of PTE (Hg, As, Cu, Zn, Cd, and Pb) were analyzed following digestion in mixture acid solution, and bioavailable PTE was extracted with a strong chelating agent (DTPA-TEA-CaCl2). The transfer factor (TF) and bioaccumulation factor (BCF) were calculated to examine the migration of PTEs in soil-plant. Hazard quotient (HQ) and total hazard index (THI) were calculated to assess the risk and migration of PTEs in soils. The results showed that PTEs in soils and plants of study area exceeded the soil background value and Hygienic Standard for Feeds. Correlation among the total Hg, As, Cu, Zn, Cd, and Pb in soils of Dongdagou stream valley was significant at p < 0.01. A good correlation was exhibited between PTEs in root/aboveground parts of plants and DTPA-soil extractable. Difference of TF and BCF was existed between Dongdagou stream valley and around Baiyin City. Hg, Cu, Zn, Cd, and Pb were mainly accumulated in soils near the mining area. The calculated THI exceeded 1, and As and Pb were the major risk factors. The ability to absorb and transfer Hg, As, Cu, and Pb of plants was lower in more serious polluted area. As had a stronger migration capacity in study area. PTEs in soils had an adverse health effect for residents, and PTEs in plants may cause toxicity to cattle and sheep.

Effects of vegetation restoration on ecosystem carbon storage and distribution pattern in semi-arid mining area

In order to explore the effect of artificial planting to promote vegetation restoration on ecosystem carbon storage in coal mining subsidence area, the distribution pattern of ecosystem carbon storage in mining area during vegetation restoration was studied by space-time substitution method.The results showed that : (1) The biomass of vegetation layer increased gradually with vegetation restoration, and the biomass distribution ratio of each component was shrub layer (92.1%) &gt; litter layer (5.5%) &gt; herb layer (2.4%). The biomass of shrub and herb layer was mainly distributed in the aboveground part, the former accounted for 73.2 %, and the latter accounted for 83.4 %. (2) The carbon content of the vegetation layer was shrub (45.5%) &gt; herb (43.6%) &gt; litter (38.7%). The total carbon storage was in the early initial of vegetation restoration (1657.1 kg hm-2) &lt; mid-term vegetation restoration (4830.6 kg hm-2) &lt; mature stage of vegetation restoration (8446.4 kg hm-2), and shrub was still the main storage part of carbon storage in this layer. In summary, vegetation restoration can significantly increase the carbon storage of the ecosystem, the proportion of carbon storage in the vegetation layer gradually increases.

Effects of Ground Subsidence on Vegetation Chlorophyll Content in Semi-Arid Mining Area: From Leaf Scale to Canopy Scale.

Ground subsidence is the main cause of vegetation degradation in mining areas. It is of great significance to study the effects of ground subsidence on vegetation. At present, few studies have analyzed the effects of ground subsidence on vegetation from different scales. However, the conclusions on different scales may differ. In this experiment, chlorophyll content was used as an indicator of vegetation degradation. We conducted a long-term field survey in the Lijiahao coalfield in China. Based on field survey data and remote sensing images, we analyzed the effects of ground subsidence on chlorophyll content from two scales (leaf scale and canopy scale) and summarized the similarities and differences. We found that, regardless of leaf scale or canopy scale, the effects of subsidence on chlorophyll content have the following three characteristics: (1) mining had the least effect on chlorophyll content in the neutral area, followed by the compression area, and the greatest effect on chlorophyll content in the extension area; (2) subsidence had a slight effect on chlorophyll content of Caragana korshins, but a serious effect on chlorophyll content of Stipa baicalensis; (3) chlorophyll content was not immediately affected when the ground sank. It was the cumulative subsidence that affects chlorophyll content. The difference between leaf scale and canopy scale was that the chlorophyll content at canopy scale is more affected by mining. This means that when assessing vegetation degradation, the results obtained by remote sensing were more severe than those measured in the field. We believe that this is because the canopy chlorophyll content obtained by remote sensing is also affected by the plant canopy structure. We recommend that mining and ecological restoration should be carried out concurrently, and that ground fissures should be taken as the focus of ecological restoration. In addition, Caragana korshins ought to be widely planted. Most importantly, managers should assess the effects of ground subsidence on vegetation on different scales. However, managers need to be aware of differences at different scales.

Prediction of Water-Blocking Capability of Water-Seepage-Resistance Strata Based on AHP-Fuzzy Comprehensive Evaluation Method—A Case Study

Coal mining under the aquifer in Northwest China has brought a series of ecological problems, such as the decline of groundwater levels and the death of surface vegetation. The study of the impermeability of rock strata between coal seams and the overlying aquifers is of great significance to solve these problems and realize water-preserving coal mining (WPCM). Based on mining-induced overburden damage and permeability deterioration, the concept of the “three seepage zones” of overburden is proposed, namely the pipe flow zone, water seepage zone and nominal water-seepage-resistance zone (NWSRZ). Meanwhile, the concept of water-seepage-resistance strata (WSRS) is put forward from the aspects of initial permeability, structural strength, swelling and the stratigraphic structure of the overlying strata. AHP-fuzzy comprehensive evaluation (AHPF) is employed to construct a model to evaluate the water-blocking capacity (WBC) of the WSRS. The model includes three secondary factors and nine tertiary indicators, and the weights and membership functions of the indicators are determined. Subsequently, the model is generalized and applied to the Yu-Shen mining area. The membership degrees are spatially visualized by means of thematic maps. The comprehensive evaluation values Φ of the WBCWSRS of 400 boreholes in the mining area under backfill mining, narrow strip mining, slice mining and longwall cave mining are calculated. Then, the Kriging method is employed to plot the zoning maps of Φ under four different mining methods. In view of different grades of WBCWSRS, three corresponding countermeasures, i.e., mining methods optimization, curtain grouting and underground reservoir construction, are put forward. The fluid–solid coupling embedded in FALC3D software is employed to establish a numerical calculation model to simulate the water table fluctuation of the underground aquifer under the four mining methods, and the reliability of the model is verified indirectly. In this paper, mathematical theory is combined with WPCM to develop an evaluation model of WBCWSRS, which provides a reference for the coordinated development of coal extraction and water resource preservation in arid and semi-arid mining areas.

Combined arbuscular mycorrhizal inoculation and loess amendment improve rooting and revegetation post-mining

Increasing the soil moisture content in the root zone and the utilization of deep soil water by plants in arid and semi-arid mining areas are very important steps in the restoration of degraded environments in mining areas. Here, the potential effects of arbuscular mycorrhizal fungal (AMF) inoculation and loess layer treatment on water and salt distribution in sand and water uptake by maize (Zea mays L.) were studied in indoor growth chamber tests combined with stable isotope methods. AMF inoculation and a loess layer both promoted the biomass and root characteristics of maize. There were good correlations between root density and soil water and salt distribution. The contribution of soil water at different depths to maize water uptake was studied using a graphical method and the MixSIAR model. AMF inoculation with a loess layer increased the percentage of water taken up by maize from depths 20–40 cm and >40 cm by 28.9% and 15.3% compared with uninoculated maize with no loess layer. AMF inoculation with a loess layer is a method suitable for revegetation of arid and semi-arid mining areas with the soil water deficit.

Downscaling Microwave Soil Moisture Products with SM-RDNet for Semiarid Mining Areas

Surface soil moisture (SM), as a crucial ecological element, is significant to monitor in semiarid mining areas characterized by aridity and little rainfall. The passive microwave remote sensing, which is not affected by weather, provides more accurate SM information, but the resolution is too coarse for mining areas. The existing downscaling method is usually pointed to natural scenarios like agricultural fields rather than mining areas with high-intensity mining. In this paper, combined with geoinformation related to SM, we designed a convolutional neural network (SM-Residual Dense Net, SM-RDNet) to downscale SMAP/Sentinel-1 Level-2 radiometer/radar soil moisture data (SPL2SMAP_S SM) into 10 m spatial resolution. Based on the in-site measured data, the root mean square error (RMSE) was utilized to verify the downscaling accuracy of SM-RDNet. In addition, we analyzed its performance for different data combinations, vegetation cover types and the advantages compared with random forest (RF). Experimental results show that: (1) The downscaling from the 3 km product with the combination of auxiliary data NDVI + DEM + slope performs best (RMSE 0.0366 m3/m3); (2) Effective data combinations can improve the downscaling accuracy at the range of 0.0477–0.1176 m3/m3 (RMSE); (3) The SM-RDNet shows better spatial completeness, details and accuracy than RF (RMSE improved by 0.0905 m3/m3). The proposed SM-RDNet can effectively obtain the fine-grained SM in semiarid mining areas. Our method bridges the gap between coarse-resolution microwave SM products and ecological applications of small-scale mining areas, and provides data and technical support for future research to explore how the mining effect SM in semiarid mining areas.

Impacts of underground coal mining on phreatic water level variation in arid and semiarid mining areas: a case study from the Yushenfu mining area, China

Impacts of underground coal mining on phreatic water level variation in arid and semiarid mining areas: a case study from the Yushenfu mining area, China

Effects of exogenous attapulgite addition on water conservation function of reclaimed soils in a semi-arid mining area

Large-scale mining has greatly damaged vegetation and caused ecological degradation in the semi-arid area in China. It is urgent to restore the vegetation to solve the deteriorating ecological and environmental problems in mining area. How to reclaim soils for effectively storing and utilizing precipitation is the primary issue for vegetation restoration in the area. In this study, we proposed to take the mixture of attapulgite clay and local sandy soils as covering materials to improve the weak water conservation function of soils in mining areas, and studied the effects of the addition of attapulgite clay on soil infiltration, drainage and water storage sampled from the Shenmu mining area. The results showed that, with increasing application rates of attapulgite clay, the cumulated infiltration volumes decreased by 4.8%-37.4%, the infiltration rates dropped by 6.4%-46.3%, the wetting front advance rates decreased by 9.8%-116.9%, the saturated hydraulic conductivities decreased by 14.3%-59.5%, the drained water volumes reduced by 0.3%-4.3% for 24 hours and by 0.3%-2.5% for 72 hours, and the maximum soil water storages increased by 1.6%-22.4%. The maximum effect of attapulgite clay peaked at the application rate of 150 t·hm-2. Considering the economic cost, the optimum application rate should be 30-150 t·hm-2. The results syste-matically revealed the mechanism of reclaiming mining soils with attapulgite clay to restore the function of water conservation, and demonstrated that attapulgite clay is an effective material for soil reclamation in the semi-arid mining area, which can provide references for soil reclamation and ecological restoration in the semi-arid mining area.

Study of plant configuration pattern in guided vegetation restoration: A case study of semiarid underground mining areas in Western China

The large-scale and high intensity mining of coal resources has further worsened the already fragile plant ecosystem in Western China. On the basis of strictly following the developmental law of regional natural ecosystems, guiding the restoration of damaged vegetation is one of the important measures for ecological restoration in mining areas. However, there are still some problems to achieve the guided restoration of damaged vegetation in semiarid mining areas: how to configure different plant species, and what is the control threshold of vegetation coverage under different site conditions among others. In this paper, based on DEM, slope, aspect and soil type data, 12 different site conditions were obtained by using overlay analysis function of ArcGIS software. The trend of interannual variation of vegetation coverage was analyzed using Landsat Normalized Difference Vegetation Index (NDVI) time series data, and the spatial distribution of areas of degraded vegetation under 12 site conditions was identified. Based on the Fully Constrained Least Square (FCLS) unmixing algorithm, typical native plants were classified using Aerial Hyperspectral data. Finally, through the comparative analysis of plant composition and abundance under 12 site conditions, the control thresholds of vegetation coverage ranged from 36.60% to 45.30% in the early stage of vegetation restoration. The thresholds of steep slope are lower than that in gentle and flat slope, which is mainly related to the fact that steep slope is more prone to soil erosion and is not conducive to the conservation of soil water and nutrients. According to the calculation results of different plant allocation proportion under 12 site conditions, the proportion of herbs and shrubs is higher than that of trees. When selecting species for vegetation configuration, native herbs and shrubs with strong adaptability, fast growth and strong drought resistance should be preferred. It is suggested that trees should be planted properly after the site conditions of vegetation growth are effectively restored or the vegetation community structure tends to be stable. In the process of vegetation restoration in semiarid mining area, not only the appropriate threshold of vegetation coverage should be considered, but also the proportion of trees, shrubs, and herbs has an important impact on the effect of vegetation restoration. The results of this paper will provide guidance for the orderly restoration of damaged vegetation in semiarid mining areas.

Influence of management on vegetation restoration in coal waste dump after reclamation in semi-arid mining areas: examining ShengLi coalfield in Inner Mongolia, China.

Conservation management usually carried out for a period of time to maintain the vegetation restoration of coal waste dumps after reclamation. However, the natural restoration of vegetation is faced with great challenges in semi-arid mining areas without management, due to the fragile ecological environment. Therefore, it is necessary to determine a reasonable management plan so that vegetation restoration can reach a stable state although the abandonment of the management. The objective was to explore the difference of vegetation restoration under different management modes in a typical semi-arid mining area. Two reclaimed coal waste dumps under different management measures, the north waste dump (ND) and the south waste dump (SD), were examined in the ShengLi coalfield in Inner Mongolia, China. The normalized difference vegetation index (NDVI) dataset based on Landsat series imagery was obtained using the Google Earth Engine (GEE) platform, and the landscape metrics were also calculated based on different vegetation coverage. The results proved that 3 years of management was not enough to stabilize vegetation restoration. A serious vegetation degradation occurred at the ND after the management stopped, with 40.1% of the pixels recorded a significant decrease (ρ = 0.05). The vegetation coverage became fragmented, and there was a tendency of succession to lower coverage. On the contrary, the vegetation restoration of SD was better under continuous management, and no significant degradation trend was observed. Furthermore, the results indicated that rainfall is the main influencing factor on vegetation restoration in semi-arid mining areas. The coal waste dump was more susceptible to weather change in natural restoration. By contrast, continuous management measures will resist such climate disturbances, even in dry years. This research will provide support for the formulation of the reclamation management plan of coal waste dumps in semi-arid mining areas.

Assessment of the environmental changes in arid and semiarid mining areas using long time-series Landsat images

Coal mining provides energy to support the development of society. However, mining affects the environment. Thus, substantial attention has been placed on environmental change in mining areas. Research assessing the environmental change in arid and semiarid mining areas has mainly been conducted by analyzing the variation in a single factor. However, the impact of coal mining on the environment is manifold, and there is no comprehensive assessment method. In this paper, we used a remote sensing index referred to as the comprehensive evaluation index (CEI) to comprehensively assess the environmental changes in arid and semiarid mining areas. The CEI in this study was calculated by integrating the changes in vegetation coverage (VC), land surface temperature (LST), and soil moisture (SM) using long time-series Landsat images. The Shendong mining area located in Northwest China was the study area. The results indicate that the environment of the Shendong mining area improved overall from 2000 to 2018. Environmentally degraded areas accounted for approximately 7.59% of the mining area and were concentrated in areas damaged by coal mining.

Characteristics and Control of Mining Induced Fractures above Longwall Mines Using Backfilling

Water conservation in mining is the key to solving the conflict between coal resource exploitation and ecological environment protection, especially in arid and semi-arid mining areas. Continuous excavation and continuous backfilling (CECB) in longwall mining is an important method to realize water conservation mining. Considering the different boundary conditions of the main roof stress in different mining phases, the mechanical models of clamped–clamped beam, continuous beam, and elastic foundation beam among filling body, main roof, and strata are established. Furthermore, the spatio-temporal evolution mechanisms of mining-induced fractures (MIF) are studied. It is found that there is a hyperbolic function relationship between MIF and the mining roadway (MR) filling percentages. Based on mining the XV coal seam under CECB in the Wangtaipu Coal Mine, the distribution patterns of MIF are studied. It is concluded that the distribution pattern is an isosceles trapezoid with the moving angle of overlying strata as the bottom angle, and the upper and lower boundary of MIF as the two parallel sides. Based on the influence coefficient of MR filling percentages on MIF, the curve of the MIF height is divided into three ranges, which include the stability control range, the critical range, and the lost control range. The controlling effects of MR filling percentages are studied, and the calculation expression of the MIF height in the stability control range is given. In engineering practice, 90% MR filling percentage is used for CECB. The MIF height is about 3.0 times of mining height, and the main roof beam is not broken. The water-resisting property of aquiclude III is not destroyed, thus, the mining does not adversely impact the water. The results provide theories and practices for controlling MIF under CECB in the conditions of extremely close distance aquifers.

EFFECT OF COAL MINING ON SOIL NITROGEN DISTRIBUTION IN SEMI-ARID MINING AREA OF WESTERN CHINA

Soil nitrogen is a key indicator of soil quality and plays a significant role for plant growth. Therefore, it is very important to study soil nitrogen distribution, especially in semi-arid area of western China. Fewer scholars paid attention to the effect on soil nitrogen due to coal mining in semi-arid mining areas of western China. In this paper, soil samples of different locations were tested in both the loess region and the aeolian sand region in the Daliuta mining area in Shaanxi Province. The impacts of mining subsidence on soil nitrogen were investigated. The soil nitrogen distributions between the loess region and the aeolian sand region were compared, and used the principal component analysis method to evaluate soil quality in semi-arid mining area. The results showed that the comprehensive score of soil quality in the loess region was as follows: the internal pulling stress zone (NLS) &gt; the external pulling stress zone (WLS) &gt; the compressive stress zone (YS) &gt; the neutral zone (ZX). The content of soil total nitrogen in YS-zone was the lowest in the loess region. The loss of nitrogen increased with time in the mining area, in which the total nitrogen loss at the depth of 0−15 cm was 0.27 g/kg, and the alkaline nitrogen loss at the depth of 0−15 cm was 1.08 mg/kg. In the aeolian sand region, the comprehensive score of soil quality was as follows: WLS &gt; FC (the non-mining zone) &gt; ZX &gt; NLS &gt; YS. The amount of soil nitrogen content in the loess region was larger than that in the aeolian sand region. It was found that for the loess region, the relationship between total nitrogen and nitrate nitrogen showed a significant positive correlation. It was also a significant positive correlation between ammonium nitrogen and alkaline nitrogen. In the aeolian sand region, there was a significant positive correlation between total nitrogen and alkaline nitrogen. There was no significant correlation among other nitrogen forms.

Effect of natural conditions and mining activities on vegetation variations in arid and semiarid mining regions

Abstract Variation in vegetation can provide fundamental information about environment and resources management, especially in mining areas with vulnerable ecosystems. Research has demonstrated that vegetation patterns across river basins, plateaus, and mountains have been affected by climate change. However, variation in vegetation caused by natural conditions and mining activities in arid and semiarid mining areas is rarely examined. Using the Yushenfu mining area as a case study, based on the Sen + Mann–Kendall method, spatiotemporal characteristics of variation in vegetation were first analyzed using normal difference vegetation index (NDVI) time series data from 2006 to 2015. For comparison, a traditional linear regression method was applied to characterize NDVI trends, indicating the feasibility of the Sen + Mann–Kendall method. Subsequently, the effect of geomorphology, groundwater depth, and drought index on NDVI was assessed. The same geomorphology or groundwater depth did not correspond to a specific NDVI value, and a relationship between the drought index and NDVI was obtained. Then, unexploited areas and mined areas were compared, revealing that mining activities have a very obvious negative impact on vegetation ecology. Furthermore, the buried depth of the eco-safety groundwater table was determined to be 1.5–5.0 m based on the curve describing the relationship between groundwater depth and NDVI. This analysis produced an ecological sensitivity map with four key zones: primary, secondary, and tertiary sensitive areas and non-sensitive areas. These results provide a theoretical basis for developing fair and equitable outcomes for mineral resource development and environmental protection.

Height of water-conducting fractured zone in coal mining in the soil–rock composite structure overburdens

Large-scale mining of coal seams gives rise to the leakage of phreatic water and further deteriorates the ecological environment of arid and semiarid mining areas in Northern Shaanxi Province. The height of the water-conducting fractured zone (WCFZ) in coal mining is the key to evaluating the presence of phreatic water leakage. This paper adopts the running water quantity of boreholes monitoring and distributed optical fiber sensing (DOFS) technology to conduct in situ measurements of the WCFZ height in soil–rock composite structure overburdens. Twenty groups of data were used to analyze the factors which influence the development height of the WCFZ and several equations are proposed to estimate the WCFZ characteristics. As indicated by the study results, the DOFS technology effectively ascertains the height of water-conducting fractures in soil and the soil layer had an obvious inhibitory effect on the height of WCFZ, with an inhibiting factor of about 0.5. The maximum relative error between predicted values and measured values was 5.34% and the relative error between predicted values and numerical simulation results was within 1.5%, verifying the accuracy of the prediction equations. The study results will help avoid water inrush hazards in mining areas and protect mining areas against ecological damages.