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Journal of Resources and Ecology >

2023 , Vol. 14 >Issue 4: 717 - 726

DOI: https://doi.org/10.5814/j.issn.1674-764x.2023.04.004

Environmental Management of Mines

Mining Rights Setting of Open-pit Coal Mines based on GIS and Environmental Impacts in Arid Areas

  • AI Xianfeng , 1 ,
  • SHI Changqing , 1, * ,
  • YANG Jianying , 1, * ,
  • ZHANG Yanqing 2
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  • 1. School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
  • 2. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
*SHI Changqing, E-mail: ;
YANG Jianying, E-mail: .

AI Xianfeng, E-mail:

Received date: 2022-10-17

  Accepted date: 2023-04-13

  Online published: 2023-07-14

Supported by

Key Research and Development Program of China(2017YFC0504403)

Mongolia Autonomous Region Science and Technology Major Project(2020ZD0021)

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Abstract

With the increasing proportion of open-pit coal mining in the coal mining industry in China, a series of potential safety hazards, environmental pollution, ecological damage and other problems caused by open-pit coal mining have attracted a great deal of attention. Scientifically determining the appropriate mining right scope of an open-pit coal mine can prevent various problems caused by coal mining from the source. In this study, according to the characteristics of open-pit coal mining and the environmental characteristics in arid areas, 15 indicators were selected and their weights were determined from the three perspectives of geological environment, social environment and ecological environment by using the AHP. Based on the spatial analysis function of ArcGIS, a digital evaluation model was established for the corresponding influencing factors, and a comprehensive evaluation model for setting the mining right range was constructed by superimposing the weights. Finally, four mining areas were identified within the study area in Wuhai, Inner Mongolia, and their ecological values were calculated to determine the mining area with the lowest ecological impact.

Key words： GIS; open-pit coal mine; mining right setting; environmental impact

Cite this article

AI Xianfeng , SHI Changqing , YANG Jianying , ZHANG Yanqing . Mining Rights Setting of Open-pit Coal Mines based on GIS and Environmental Impacts in Arid Areas[J]. Journal of Resources and Ecology, 2023 , 14(4) : 717 -726 . DOI: 10.5814/j.issn.1674-764x.2023.04.004

1 Introduction

In recent years, China’s coal industry has developed rapidly due to the safety and efficiency of open-pit coal mining, large production scale, and a high resource recovery rate (Tian et al., 2014; Li et al., 2019). In China’s Coal Industry Policy and mining area planning and design, open-pit mining is the preferred mining method under the right geological conditions. However, with the development of the social economy, many problems have emerged. 1) Due to the late study of relevant regulations on mining right setting and the complexity of mining right setting factors in China, the spatial layout of the mining right scope setting has been relatively random, and the problem of the spatially interactive distribution of mining rights is serious, which not only increases the likelihood of safety accidents, but also may cause direct or indirect impacts on surrounding residents, and even threaten social stability. 2) Open pit mining will cause outstanding environmental problems, such as water and soil loss, vegetation damage and air pollution. Compared with coal mines, coal open-pit mining often causes more extensive damage to the regional ecology, atmosphere, soil and other environments. With the continuous expansion of the construction level of ecological civilization in mining areas, the concept of sustainable development with a goal of “green mines” has become the consensus of the industry. As the first step of mine planning and development, reasonable mining right setting is the key component of green mining and sustainable development in the mining area. Before the setting of mineral rights in China, the attention paid to this issue was not very high, because the setting of mineral rights can bring economic benefits to enterprises.
The research on the setting of mining rights only began after the original Ministry of Land and Resources issued the Notice on Doing a Good Job in the Relevant Work after the Approval or Cancellation of the Record Approval of the Mining Rights Setting Scheme (GTZG [2015] No.2) in 2015, when scholars began to pay attention to this issue and conduct research (Niu and Wu, 2020). In recent years, foreign research has focused on integrating the environment and public health into the planning, and exploring the development route of mineral resources with interdisciplinary fields, information synthesis and spatial analysis technology as the core idea. The setting and comprehensive evaluation of mining rights is a relatively new field, and most of the research is still conducted at a large scale or in large scale areas, such as regional resources or cities and counties. However, the setting of mining rights is planned in a small scale in the mining area, involving either a single mine or multiple adjacent mines. Therefore, large scale evaluation factors may not be suitable for evaluating the rationality of a single mining right, and the research in this area is still lacking. In addition, with the developments and innovation in the field of information technology, mineral resource planning and evaluation in recent years have been influenced by computer science.
This study used a combination of traditional planning and information technology to screen the mining right setting environmental impact indicators from the perspective of ecological protection and restoration, to interpret the indicators on the platform of GIS software, and to build the evaluation model of mining right setting in combination with AHP. In addition, the environmental cost was introduced to calculate the environmental impact value of the mining right scheme, so as to achieve “giving consideration to both economic and environmental benefits”. This study mainly solves two problems: How the location and scope of mining rights should be delimited in order to have less impact on ecological protection and restoration; and How many mining rights should be set in a deposit for the most reasonable economic and environmental benefits? The results of this study provide a scientific basis for setting the mining right scope in open-pit coal mines.

2 Materials and methods

2.1 Background of the study area

Due to the influences of human geography, geology, social economy, government policies and other factors, there are deviations in the setting of mining rights in different regions. Therefore, the authors take Wuhai Open-pit Coal Mine in the northwestern arid area of western Inner Mongolia as the research object, and a specific mining area as an example for analyzing the proposed scope of mining rights. The study area selected includes the current mining area and the surrounding 5 km potential impact area. The specific location diagram is shown in Fig. 1. The study area is in an extremely arid desert area, with low precipitation, high evaporation, dry and windy weather, long sunshine time, strong solar radiation, large temperature differences between day and night, no obvious surface water system, seasonal runoff, usually dry conditions year round without water, and a short period of surface flow forms after rainstorms. The current mining area is outside of the ecological protection red line, permanent basic farmland and urban development boundary, so it does not involve illegal occupation of protected areas, farmland or urban areas. The surrounding area of the mining area is sparsely populated with scattered residents, who are mainly engaged in animal husbandry, as well as planting and breeding. However, because the ground is mostly exposed bedrock or distributed Quaternary sand gravel, the agriculture and animal husbandry are underdeveloped.
Fig. 1 Research area map
The lithological characteristics of the stratum are relatively simple. According to the Code for Hydrogeological Engineering Geological Exploration in Mining Areas (GB12719-91), it is a simple deposit of layered rock type, and the hydrogeological type is the simple type with hydrogeological conditions of fissure water filling deposit. The study area belongs to the Zhuozishan coalfield, the geotectonic unit is North China Platform (Grade I), Western Ordos depression (Grade II), and the Grade III tectonic unit is the Zhuozishan fold fault bundle. The stratum has a generally monoclinal structure inclined to the southwest, and the rock stratum trend is mostly NW12°‒15°. The shallow area near the south turns to NW40º with a dip angle of 6°‒10°.

2.2 Methods for setting the scope of the mining right

The setting of the mining right shall follow the “Technical Requirements for Zoning of Mining Right Setting”, National and local government policy requirements, deposit occurrence conditions, geological structure, landform, and mining function requirements, as well as the impact of coal mining on the surrounding environment and other factors. The economic value of the mining right itself was not considered in this study, and the factors that may affect or counteract the mining right setting were selected by consulting the literature and the mining right setting scheme. Through field inspections and expert discussions at more than ten open-pit coal mines in Wuhai City and Ordos City in the region, the relatively important factors affecting the setting of the mining right scope in the region were obtained. The evaluation index system was constructed from three perspectives, a single factor evaluation model was established based on GIS and a comprehensive evaluation model was constructed by combining the overlapping weighted reconstruction of the analytic hierarchy process. Finally, the environmental cost estimations of land compensation, water pollution control and air pollution control for the different schemes provided scientific guidance for the setting of the mining right scope of the open-pit coal mines in this area. Due to different regional characteristics, there will be great differences in the selection of influencing factors, determination of weights and estimation of environmental costs in different regions. The construction process of the mining rights setting evaluation system is shown in Fig. 2.
Fig. 2 Process for construction of the final evaluation system

2.2.1 Index selection and system construction

The setting of mineral rights is a comprehensive spatial decision-making problem involving multiple levels and factors. This study did not consider the economic value of the mining right itself, but only considered the many external environmental factors. Therefore, the natural geological and environmental factors are the main factors, and the human activities of social attributes are the auxiliary factors. In addition, the impact factors were preliminarily screened by referring to the Technical Requirements for Zoning of Mining Right Setting, the Code for Investigation and Assessment of Geological Environment of Mines, the environmental impact assessment of mineral resources planning and other achievements. Additional data were obtained through on-site investigations of more than 20 small and medium-sized open-pit coal mines in Wuhai and Ordos cities in the northwestern arid region, and discussions with some group chief engineers, coal mine directors, technicians, and personnel in the fields of geology, safety engineering, and water conservancy departments. Based on the analysis of existing problems and influencing factors of the Wuhai Open-pit Coal Mine, 15 environmental influencing factors were finally obtained through discussions on the indicators that had overlapping and ambiguous meanings.
The index system for setting the mining right of the open-pit coal mine was based on the following six aspects.
(1) Occurrence conditions of coal seams. The existence of coal resources is the basis of the scope of mining rights. Generally, mine development and construction can only be carried out after a comprehensive geological survey by means of drilling and trenching, and the degree of exploration must reach or be above the level of a detailed survey and also meet the conditions for mine development and construction. Unlike the entire mining area, the scope of the mining right is smaller, while the scope of the open-pit coal mine mainly includes the scope of open-pit stripping and mining of the coal resources.
(2) Engineering geological conditions. This factor mainly includes lithological characteristics, geological structure, surface geological process, landform and other conditions. The division of these conditions is an important factor affecting the division of the mining rights. The geological factors affect each other and comprehensively determine the safe production and ecological damage scope of the mining area.
(3) Physical geographical elements. As for the unique arid climatic conditions in the northwestern arid area, vegetation coverage is the key consideration in order to realize the construction of green mines. It is necessary to comprehensively consider the safe distances that need to be maintained in fire belts, dry lands, barren mountains, streams and lakes, ore body storage areas and miner living areas, and estimate the sizes of their acquisition costs, in order to obtain a relatively low economic scale and minimize land occupation and damage.
(4) Impact on the ecological environment. The ecological impact of coal mining must consider many aspects. In terms of the atmospheric environment, coal dust pollution can pose a threat to the mining area and even the regional environment. In terms of the water environment, industrial wastewater may damage the quality of regional water bodies. In terms of land resources, various land types and ecological function zoning should be considered.
(5) The impact on human society. Mine construction and mining require the layout of infrastructure, mainly for the water supply and the power supply, which is a necessary prerequisite for the construction and development of the mining area. For open-pit mines, the safety impact of blasting on human activities must be considered. For residential conditions, the pollution sources caused by wind direction, the noise generated by blasting, and the safe distance from residential areas specified in the mine safety regulations must be considered.
(6) Flexibility factor. The unreasonable division of many mining rights may occur if the protection area, red line area, traffic arteries, community environment, land use classification, geographical location of the mining area, and other factors are not comprehensively considered. As a result, many mining rights settings do not meet the national or regional policy standards, and different buffer distances should be selected according to the policy specifications.
By screening the indicators in discussions with experts from various fields such as the Resource Bureau, mine managers, coal mine environmental safety technicians, and engineers, the final evaluation index system was established based on three standard layers and 15 indicators.
Table 1 Index system for setting the mining right scope
Target layer Criterion layer Indicator layer
Establishment of the mining right of an open-pit coal mine Geological safety environment (B1) Geological structure (C11)
Topographic features (C12)
Hydrogeology (C13)
Lithological characteristics (C14)
Ramp structure (C15)
Coal seam hosting (C16)
Social environment (B2) Ground features (C21)
Transportation conditions (C22)
Hydroelectric conditions (C23)
Noise pollution (C24)
Ecological environment (B3) Coal dust pollution (C31)
Water pollution (C32)
Ecological function zoning (C33)
Land occupation and damage (C34)
Vegetation cover (C35)

2.2.2 Mining right setting model

The basic data such as information on geology, climate, society, humanities and remote sensing images in the study area were obtained from the Natural Resources Bureau, Geological Survey Bureau, Geo-spatial Data Cloud, and the Mapgis and survey data of the agriculture, forestry and water departments. According to the final list of selected influencing factors in the indicator layer, as interpreted in ArcGIS, the remote sensing image was subjected to radiometric calibration, atmospheric correction, image fusion, mosaic, cropping, and resampled to improve the stacking analysis accuracy. The basic types of GIS modeling included binary model, exponential model, regression model and process model. The purpose of this study is to highlight the appropriate areas and discard the inappropriate areas. Since the exponential model generates an index value in each pixel area, which can more clearly distinguish the weight superposition results of the various influencing factors, the exponential model was adopted. The construction of information interpretation and evaluation model is shown in Fig. 3.
Fig. 3 Information interpretation and evaluation model building ideas
Interpretation and quantification of the modeling factors
(1) Digital Deposit Model. The construction of the deposit model is mainly based on the data of boreholes and trenches. From the mining software, we can model the stratum conditions and the occurrence of coal seams, obtain the scope of the deposits, and extract the scope of deposits for importing into ArcGIS. We assigned a value of 2 within the range, and set a 500 m buffer, then assigned a value of 8 within the buffer and a value of 32 outside the buffer.
(2) Digital Surface Feature Model. The surface feature factors must be based on regional policies and local planning in order to achieve “multi compliance”. According to the requirements of different specifications, a suitable buffer range was selected for a multi-ring buffer zone analysis. According to the index model assignment standard, the assignment was 32 within the boundaries of each buffer zone, and 2 outside the boundaries of the buffer zone. The assigned value was 32 within the boundaries of the nature reserve, wetland park, desert park and forest park, and 2 outside those boundaries.
(3) Digital Slope Model. According to the gradient grading in “General Rules for Planning of Comprehensive Water and Soil Conservation (GB/T15772‒2008)”, the slope can be divided into categories of small slope<5°, gentle slope 5°‒8°, gentle slope 8°‒15°, steep slope 15°‒25°, steep slope 25°‒35° and steep slope>35°. The evaluation values assigned to the reclassification of the different grades were 2, 4, 8, 16, 32 and 32, respectively.
(4) Digtal Ramp Model. The slope structure was divided into dip slope, cross slope, transverse slope, reverse slope and escarpment slope. After reclassification, the evaluation values of 16, 16, 4, 16, 8 were assigned, respectively.
(5) Digital Lithological Model. The basic quality indexes of rock mass determined according to the basic quality classification in the Standard for Classification of Engineering Rock Masses (GB50218‒94) are divided into Grade I, Grade II, Grade III, Grade IV and Grade V strengths, which were assigned in this study as 2, 4, 8, 16 and 32, respectively.
(6) Digital Hydrological Model. Hydrologic analysis mainly extracts gully density and catchment accumulation. The northwestern arid desert region has limited rainfall and a poor water supply capacity. In the case of rainfall, the confluence is mainly a trunk confluence, which will cause potential safety hazards, while the branch trunk is basically free of confluence, and the branch trunk is mostly in the valley section, which is suitable for the boundary of mineral rights. Therefore, the evaluation values were set as 32 at the main confluence, 2 at the tributary confluence and 8 in the other areas.
(7) Digital Tectonic Model. Existing research suggests that the buffer zone distance should be set to 300 m-600 m as the starting distance (Cui et al., 2020). For the convenience of buffer zone analysis, this study used 500 m as the starting point of the buffer distance, and the buffer distances were set as 500 m, 1000 m, 1500 m, 2000 m and above 2000 m, respectively. Because the fault is usually set as the boundary of the mining right, the reclassification assignments were 32, 16, 8, 4, and 2.
(8) Digital Road Network Model. The same processing method can be used for the digital terrain and digital structure model. The buffer distances were respectively set as 500 m, 1000 m, 2000 m, 4000 m and above 4000 m, and the corresponding reclassification assignment values were, respectively, 2, 4, 8, 16, and 32.
(9) Digital Land Model. In this study, the types of land use in mining areas were divided into cultivated land, forest land, grassland, water area, residential area, industrial and mining land and bare land. In addition to considering the costs of the different types of land acquisition, the dry and rainless climatic conditions in the northwestern arid region should also be taken into account, and the damage to the original ecological land should be reduced to a greater extent. The following values were assigned: 32 for cultivated land and water area, 16 for forest land and residential area, 8 for grassland, 4 for bare land, and 2 for industrial and mining land, which belongs to normal coal mine construction land.
(10) Digital Noise Model. Most noise monitoring software today, such as Cadna/A (Zhou, 2009), supports the export of the shp format. After the simulation is completed, that is, the noise contour map in vector format reflecting the noise intensity level can be obtained, then the digital noise model can be established by reclassification in ArcGIS according to the specifications and standards.
(11) Quantification of the ecological functional areas. This mainly refers to areas that play an important role in water and soil conservation areas, windbreak and sand fixation areas, water conservation areas and biodiversity conservation areas. In general, the development and construction activities are mainly protected and restricted in such areas, which has a great impact on mining development activities.
(12) Digital Vegetation Model. The threshold divisions of vegetation coverage refer to the threshold divisions of desert vegetation in the northwestern desert area by Zhou et al. (2015): fc<0.1 is bare land; 0.1≤fc<0.25 is desert vegetation with low coverage; 0.25≤ fc≤0.35 refers to desert vegetation with high coverage; and fc>0.35 refers to non-desert vegetation (i.e., forest, grass, farmland, etc.). Based on the difficulty of vegetation growth and restoration in arid areas, the reclassification values were 2, 8, 16, and 32, respectively.
(13) Coal dust pollution. According to the “Regulations on Environmental Protection Design of Construction Projects”, “Technical Methods for Establishing Local Emission Standards for Air Pollutants (GB/T13201‒91)” and local policies, health protection zones and greening measures were set up (Yang, 2001). For the downwind residential area, buffer zones of 1000 m, 2000 m, 3000 m, 4000 m and above 4000 m were set, and their corresponding assigned values were 32, 16, 8, 4 and 2, respectively.
When quantifying and reclassifying some indicators, a specific analysis should also be conducted according to the actual local conditions.

2.2.3 Estimation of coal resource benefit and environmental value

The main environmental costs that affect the ecological protection and restoration of mines in the region were selected, including land compensation costs, air treatment costs, water treatment costs and ecosystem service value. Various value estimation standards were selected from previous research results (Ye et al., 2019), and the parameters were modified to adapt to the regional conditions.
(1) Coal resource value estimation
Because there are usually safety pillars and blank areas between mining rights, different mining right settings mean that there will be a certain amount of coal resource loss, so it is necessary to estimate the value of coal resources. The coal value was estimated using the contents of the Mineral Resources and Equity Theory, written by Zhu (2008) of the China University of Mining and Technology:
${{V}_{C}}=\alpha \times {{Q}_{C}}+\theta \underset{i=1}{\overset{n}{\mathop \sum }}\,\frac{\beta P{{Q}_{i}}}{{{\left( 1+r \right)}^{i}}}$
where VC is the total value of coal reserves, α is the geological exploration fee per ton of resources; QC is the resource reserve; Qi is the estimated coal resource recovery; β is the proportion of value to sales revenue that should be included in the value of coal resources in order to enable the coal industry to enjoy the average profits of industrial enterprises; P is the sales price of raw coal in the study area; r is the discount rate; and θ is the cost variance rate. For the specific coefficients, refer to “China Mining Yearbook” and “China Mineral Resources Report” over the years of the study. α followed the research results of Ye et al. (2019), and the value (Geological exploration fee) was 0.068 yuan t-1. The value of β was determined based on the coal industry and industrial sales revenue and profit for a total of five years from 2016 to 2020. Details can be found in Table 2.
Table 2 Comparison of product sales revenue and product sales profit between the coal industry and national industrial enterprises
Year Coal industry National industrial
enterprises
Sales
revenue		 Total profit Coal
output		 Sales
revenue		 Total profit
2016 22328.5 1159.5 33.6 1158998.5 71921.4
2017 24870.6 2952.7 34.5 1133160.8 74916.3
2018 24645.8 2888.2 36.8 1049490.5 66351.4
2019 21990.1 2837.5 38.5 1067397.2 65799
2020 20821.6 2221.6 39 1083658.4 68465
Average 22931.3 2411.9 36.5 1098541.1 69490.6

Note: Data sources: China Statistical Yearbook and China Mineral Resources Report from 2016 to 2020. The units in the table are in billions of yuan.

The average sales profit rate of industrial enterprises nationwide from 2016 to 2020 was 6.326%. After several iterations, when β=0.041, the sales profit margin error of the coal industry was 6.309%. This is close to the average sales profit margin of the national industrial enterprises, the approximate degree of the average sales profit of the national industrial enterprises is high, and the error is small, so the β value was set as 0.041.
In 2020, the national average price of coal was 639.6 yuan t-1, with a discount rate of 4.9% and a cost variance rate of 1.39.
(2) Land compensation cost
Land compensation fees mainly include land occupation fees and land management fees (Wang et al., 2019). The cost of the land needed for mines occupied by open-pit mining is the cost of mine land occupation. For open-pit mines, the land occupation of the mining right is usually all paid at one time, so the land occupation cost is:
${{V}_{Z}}={{C}_{Z}}\times {{A}_{Z}}$
where VZ is the land occupation fee, yuan; CZ is the cost of land acquisition, yuan ha-1; and AZ is the floor space, ha.
The land treatment cost is mainly the cost of surface ecological restoration after open-pit mining. This study refers to the results of a study from the mineral resources ecological compensation mechanism and policy research project of the China Council for International Cooperation in Environment and Development as the measurement standard. The surface ecological restoration cost VZ is expressed in terms of coal reserves within the mining right boundary and different landforms in different regions. The study area is located in the west of Inner Mongolia in the northwestern region, and the landform is hilly, so the ecological restoration cost was set at 6.16 yuan t-1.
(3) Air treatment cost
Coal dust, SO2, NOX, PM10 and other air pollutants generated from open-pit mining will lead to a decline in air quality, making people vulnerable to pneumoconiosis diseases. The cost of air pollution is estimated mainly from the loss of living welfare and human health, the cost of pollution cleaning and the loss of less polluted agricultural production. Drawing on the research results from Shanxi (Dang et al., 2007), and according to the consumer price index of the China Statistical Yearbook 2021, the consumer price index of 2020 will be 686.5. Taking inflation into account, the air loss caused by mining each ton of coal in 2020 was 9.51 yuan.
(4) Water pollution control cost
The western part of Inner Mongolia is a typical arid area that is characterized by low total precipitation and an insufficient water supply. However, the mining of 1 t coal requires 2.5 t water (Bureau of Quality and Technical Supervision of Inner Mongolia Autonomous Region, 2009). Therefore, the total amount of wastewater discharged can be calculated according to the quantity of coal mined in the mining area. The calculation of the water pollution control cost is as follows:
VQ=M×A
where VQ is the total cost of wastewater treatment; M is the unit restoration cost of water resources; and A is the amount of discharged wastewater.
Similarly, based on the coal mining water pollution in Shanxi in 2003, the loss per ton of coal is 3.3 yuan t-1, so the mining water pollution in 2020 was set in this study as 5.16 yuan t-1.
(5) Ecosystem service value
According to the ecosystem service value equivalence table established by Costanza et al. (1997) and Xie et al. (2008), and in combination with previous research results (Li et al., 2019; Yori et al., 2019), the economic value of one ecosystem service value equivalent factor was determined according to the average grain production of several cities in the arid region of Inner Mongolia, in order to obtain the ecosystem service value per unit area of each land type. Using data from the statistical yearbook of cities in arid areas of Inner Mongolia in 2018 and the National Grain and Oil Information Center, the average annual grain output in arid desert areas of western Inner Mongolia was calculated to be 4418 kg ha-1. According to the annual data of each city, corn is the main crop in the region, accounting for 80%. Therefore, taking the average price of corn in the same year (1.7 yuan kg-1) as the base price, the economic value of an equivalent factor in the study area was 1072.94 yuan ha-1. On this basis, the ecosystem service value coefficient per unit area of each land use type in the arid desert region of western Inner Mongolia was obtained.
Table 3 ESV coefficients of the various land use types in western Inner Mongolia
Ecological service function Cultivated land Woodland Grassland Bare ground Industrial and mining land Waters
Gas conditioning 718.87 1512.85 2113.69 118.02 826.16
Climate regulation 386.26 4538.54 5590.02 107.29 2457.03
Food supply 912.00 203.86 407.72 10.73 10.73 858.35
Water conservation 289.69 3594.35 4098.63 225.32 ‒8057.78 109697.39
Soil conservation 1105.13 1845.46 2575.06 139.48 21.46 997.83
waste disposal 107.29 1373.36 1845.46 332.61 ‒2639.43 5954.82
Bio-diversity 139.48 1684.52 2339.01 128.75 364.80 2027.86
Aesthetic landscape 64.38 740.33 1030.02 53.65 10.73 2736.00
Raw material production 429.18 461.36 600.85 32.19 246.78
Total 4152.28 15954.62 20600.45 1148.05 ‒10289.49 125802.22

3 Results and analysis

According to the actual situation in the proposed mining right area, there is no need to analyze the lithology, hydropower conditions, groundwater, coal dust and dust pollution or other factors. As the drilling trench information is confidential, the density analysis was only conducted according to the drilling location. The indicators ultimately selected include drilling information, structural conditions, hydrological conditions, slope structure, slope, ground features, road network, land occupation, ecological functional areas, and vegetation coverage. Then the corresponding digital model was constructed according to Figs. 4-11.
Fig. 4 Digital fault model

Note: Please refer to Table 4 for the value information in the right.

Fig. 5 Digital hydrological model

Note: Please refer to Table 4 for the value information in the right.

Fig. 6 Digital slope model

Note: Please refer to Table 4 for the value information in the right.

Fig. 7 Digital land model

Note: Please refer to Table 4 for the value information in the right.

Fig. 8 Digital drilling model

Note: Please refer to Table 4 for the value information in the right.

Fig. 9 Digital ramp structure

Note: Please refer to Table 4 for the value information in the right.

Fig. 10 Digital vegetation model

Note: Please refer to Table 4 for the value information in the right.

Fig. 11 Digital road network model

Note: Please refer to Table 4 for the value information in the right.

Table 4 Assignments of the evaluation factors for the mining rights setting model
Influence factor Evaluating indicator Evaluation and assignment of evaluation factors for the mining right setting model Weight
Excellent Good Moderate Poor Extremely poor
Geological safety Borehole density >2.5 holes km-2 2‒2.5 holes km-2 1.5‒2 holes km-2 1‒1.5 holes km-2 <1 holes km-2 0.1394
Distance from fault >2000 m 1500‒2000 m 1000‒1500 m 500‒1000 m <500 m 0.0782
Hydrology Ramus Other Trunk 0.0962
Ramp structure Transverse slope Escarpment slope Dip, cross and reverse slope 0.0321
Slope <5° 5°‒8° 8°‒15° 15°‒25° >25° 0.0827
Social
environment		 Ground features Other than rigid factors Within the rigidity factors 0.0952
Distance from road <500 m 500‒1000 m 1000‒2000 m 2000‒4000 m >4000 m 0.0476
Ecological environment Land occupation and damage Industrial and mining land Nudity Grassland Forest land,
residential area		 Water area,
cultivated land		 0.1405
Ecological functional area General important area Important area Extremely
important area		 0.1119
Vegetation cover Low coverage Middle coverage High coverage 0.1761
Assignment 2 4 8 16 32 1
Based on the reclassification of each grid factor, combined with the weight coefficient value of each factor calculated by the analytic hierarchy process, the comprehensive evaluation and assignment of the mineral right setting were obtained for each factor grid layer according to their weight ratio and weighting. The evaluation values are divided into 2-4, 4-8, 8-16 and 16-32, and the corresponding evaluation results are excellent, good, poor and extreme. According to the characteristics of the index model, when an evaluation value is greater than 8, that is, when the evaluation result is poor or extremely poor, the situation is not suitable for setting the mining right. The stacking weight analysis results are shown in Fig. 12.
Fig. 12 Evaluation diagram of the scope of mining rights
Note that the mining right range after the superposition analysis of various factors may be not compact in space, irregular in layout or divided into complete patches, while the boundary set by the mining right is oriented toward implementation management and practical application. Therefore, the boundary based on management implementation needs to be adjusted according to the actual situation of roads, village boundaries, mountains and other natural boundaries in combination with high-definition satellite images in the study area. The revised scopes of the four proposed mining rights are shown in Fig. 13.
Fig. 13 Mining right scope setting scheme
We can then estimate the recoverable reserves of each scheme. Due to confidentiality, only part of the mineral reserve information is available. On this basis, the reserves in the mining area are estimated to be 51.5 million tons of coal resources. Meanwhile, for the convenience of the calculation, the mining life of each scheme is assumed to be the same, and the impact life of ecosystem service value destruction is the same as the mining life. The results of benefit estimation for the different mining rights are shown in Table 5.
Table 5 Benefit estimation of the mining rights scope setting scheme
Types Number of
mineral rights (piece)		 Recoverable
reserves		 Total value of
reserves		 Land
compensation		 Atmospheric control Water pollution control Ecosystem
service value		 Benefit
Plan 1 1 5150.0 188071.8 31724.0 48976.5 66435.0 16981.0 23955.3
Plan 2 2 4858.2 177415.7 29926.6 46201.7 62670.7 15903.9 22712.8
Plan 3 3 4559.3 166500.2 28085.5 43358.9 58815.0 15498.9 20741.9
Plan 4 2 4851.1 177156.3 29882.8 46133.9 62579.2 16612.1 21948.0

Note: The unit of the benefit estimation is 10000 yuan.

Note that in several mining right setting modes with different quantities and ranges, the comprehensive benefits are in the sequence of scheme 1>scheme 2>scheme 4>scheme 3. Therefore, from the perspective of the combined comprehensive benefits of economic benefits and environmental benefits, when setting the mining rights in this area, the overall benefit of setting one mining right in scheme 1 is the best.

4 Conclusions and suggestions

(1) This study used the western part of Inner Mongolia as an example, and constructed an evaluation system for mining right setting of open-pitcoal mines in the northwestern arid region based on the regional characteristics of this arid region. GIS was used to extract the spatial attribute information of various environmental impact indicators, and its spatial analysis and other functions were then combined with the AHP to establish the setting model of the mining right scope. This approach effectively divided the appropriate scope of the mining right, making up for the traditionally cumbersome paper map analysis in which it is difficult to integrate any defects. Finally, because there are many different plans for setting the mining right scope in space, this study introduced the combination of environmental costs and economic benefits, and modified the various cost standard parameters based on the characteristics of the study area. This allowed us to explore the total benefits after multi-objective decision‒making, which simplifies the process to a certain extent, saves human resources, and has a certain application effect.
(2) The proposed mining right in an actual mining area is demonstrated as an example. Based on the established mining right setting model and the actual situation of the proposed mining right, the scopes of four proposed mining rights were obtained and the benefits were compared. In addition, since forest land, grassland, water area and other types of land ecosystems have a great impact on this area, when setting the scope of mining rights in this area, it is necessary to avoid the occupation of these types of land.
(3) Due to some confidentiality and precision gaps in the data used in this study, the use of ArcGIS for analyzing the scope of mineral rights may have some inaccuracies, which may lead to some errors in the analysis results. In addition, the actual environmental cost introduced in the setting of mining rights, which is the main impact of coal resource mining, is still much larger than the estimated environmental cost, and the method of using economic and environmental benefits to choose the setting of mining rights is still one‒sided. The setting of mining rights is a complicated process, and its value measurement is also multi-faceted.

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