Ecological environment quality evaluation and evolution analysis of a rare earth mining area under different disturbance conditions

Evaluation and dynamic monitoring of ecological environment quality in mining area based on improved CRSEI index model

Large-scale open-pit mining in mining areas will cause serious damage to the ecological environment. Building a "green mine" is an essential part of implementing sustainable development. In order to explore the changing characteristics of the environmental quality of the open-pit mining area and provide a scientific basis for improving the ecological environment of the mining area. Taking Sijiying open-pit mining area as the research area, based on four Landsat images from 2000 to 2022, the four index components of greenness, humidity, dryness and heat were integrated, and an improved remote sensing ecological index CRSEI was constructed by principal component analysis to dynamically evaluate and monitor the ecological environment quality of the mining area. The results show that the average correlation between CRSEI and the index components is higher than the average correlation between the components, indicating that it has a favorable expression effect on the ecological quality of the mining area. The ecological environmental quality of the study area experienced a shift to the poor grade, and the poor ecological quality area was mainly distributed in industrial and mining land and construction land, with the mean CRSEI of 0.668, 0.474, 0.460 and 0.494, respectively. The results of dynamic monitoring showed that the proportion of ecological improvement area (41.43 %) was greater than that of ecological deterioration area (33.29 %) in the study area in the past 22 years, and additional restoration efforts should be made to achieve sustainable development of the ecological environment.

An investigation into the disturbance effects of coal mining on groundwater and surface ecosystems

Coal mining disturbs surface ecosystems in coal mining subsidence areas. Based on the groundwater-surface composite ecosystem analysis, we constructed an ecological disturbance evaluation index system (18 indices) in a coal mining subsidence area using the analytic hierarchy process (AHP). Taking the Nalinhe mining area in Wushen Banner, China, in 2018-2020 as an example, the weight, ecological disturbance grade and correlation of different indicators were determined by implementing fuzzy mathematics, weighting method, and correlation analysis method. The major conclusions of this review were: (i) After two years of mining, ecological disturbance was the highest in the study area (Grade III) and the lowest in the non-mining area (Grade I). (ii) Coal mining not only directly interfered with the environment, but also strengthened the connection of different ecological indicators, forming multiple ecological disturbance chains such as "mining intensity-mining thickness-buried depth/Mining thickness", "coal mining-surface subsidence-soil chemical factors", and "natural environment-soil physical factors". The disturbance chain that controls the ecological response factors in the region remains to be determined. However, the ecological response factors are the most important factor that hinders the restoration of the ecology in a coal mining subsidence area. (iii) The ecological disturbance in the coal mining subsidence area continued increasing over two years due to coal mining. The ecological disturbance by coal mining cannot be completely mitigated by relying on the self-repair capability of the environment. This study is of great significance for ecological restoration and governance of coal mining subsidence areas.

Quantifying the coal mining impact on the ecological environment of Gobi open-pit mines

Xinjiang is a coal-rich region with many bare rocky and gravelly areas with a delicate and fragile ecology. What is the ecological impact of mining activities? In this study, the Salinity Index (SI-T), New Gravel Land Index (NGLI), and Land Deterioration Index (LD) were used to establish an improved remote sensing ecological index (IRSEI) for the HongShaQuan open-pit coal mine (HSQ). The spatial and temporal evolution of the ecological environment of the HSQ was revealed by IRSEI and unary linear regression analysis. Moreover, the influence of mining on the ecological environment of the Gobi mining area was quantitatively evaluated by the random forest model (RF) and difference-in-difference (DID) approach. The results indicated that the value of IRSEI in HSQ had typically decreased over the last 30a. The ecological environment in most areas of the study area was poor and fair levels. The ecological environment of the whole study area showed a decreasing pattern from southeast to northwest. The proportion of degraded area (52.33 %) was much higher than that of improved area (0.39 %). The average residual before and after mining in HSQ were -0.1011 and -0.2323, respectively, which were much higher than that of the whole study area (-0.0330 and -0.0658, respectively), indicating that the mining activities in HSQ harmed the ecological environment and aggravated the degradation of the ecological environment. The impact of mining activities on the ecological environment from 2000 to 2021 was -0.138 using DID. The results from the multiple regression model (MR), RF, and DID during the pre-mining period (2000-2011) were -0.0709, -0.1011, and -0.1345, respectively, while they became -0.1765, -0.2323, and -0.1963 during the post-mining period (2012-2020), respectively. The latter was worse than the former, all showing that the mining activities of HSQ had resulted in a negative effect on the ecological environment. It also demonstrated that the negative value of mining from the MR, RF, and DID have a very similar change trend and was near in value. This verified the feasibility of DID and RF in quantitative analysis of the ecological environment. The ecological environment quality of HSQ was mainly affected by climate change, and less influenced by mining, the contribution rates of both in the IRSEI improved area were 88.48 % and 11.52 %, respectively; and in the degraded area were 69.45 % and 30.55 %, respectively. Therefore, the Gobi mining area should pay attention to the protection of the ecosystem while developing coal. Planting vegetation can promote the governance and restoration of the ecological environment in the mining area.

Evaluation of Remote Sensing Ecological Index Based on Soil and Water Conservation on the Effectiveness of Management of Abandoned Mine Landscaping Transformation

Abandoned mines are typical areas of soil erosion. Landscape transformation of abandoned mines is an important means to balance the dual objectives of regional ecological restoration and industrial heritage protection, but the secondary development and construction process of mining relics require long-term monitoring with objective scientific indicators and effective assessment of their management effectiveness. This paper takes Tongluo Mountain Mining Park in Chongqing as an example and uses a remote sensing ecological index (RSEI) based on Landsat-8 image data to assess the spatial and temporal differences in the dynamic changes in the ecological and environmental quality of tertiary relic reserves with different degrees of development and protection in the park. Results showed that: ① The effect of vegetation cover, which can significantly improve soil and water conservation capacity. ② The RSEI is applicable to the evaluation of the effectiveness of ecological management of mines with a large amount of bare soil areas. ③ The mean value of the RSEI in the region as a whole increased by 0.090, and the mean values of the RSEI in the primary, secondary and tertiary relic reserves increased by 0.121, 0.112 and 0.006, respectively. ④ The increase in the RSEI in the study area is mainly related to the significant decrease in the dryness index (NDBSI) and the increase in the humidity index (WET). The remote sensing ecological index can objectively reflect the difference in the spatial and temporal dynamics of the ecological environment in tertiary relic protection, and this study provides a theoretical reference for the ecological assessment of secondary development-based management under difficult site conditions.

A Remote-Sensing Ecological Index Approach for Restoration Assessment of Rare-Earth Elements Mining

In order to meet the requirements for comprehensive and multidimensional generalization of ecological management effectiveness evaluation indexes in the context of ecological restoration advocating comprehensive management by multiple means, this paper explores the rationality of using RSEI as an ecological management effectiveness evaluation index to adapt to the systematic transformation of the management goal of abandoned mine restoration from ecological restoration to regional socioeconomic sustainable development. Based on Landsat-8 image data, the remote sensing ecological index (RSEI) was used to evaluate the dynamic changes and spatial and temporal differences of the ecological environment in the study area under the long-term multimeans comprehensive management. The RSEI is suitable for evaluating the effectiveness of comprehensive ecological management in mining areas with a large amount of bare soil. The regional RSEI mean value increased by 0.029 in the early stage and 0.051 in the later stage by fragmentation management, indicating a better effect of multimeans comprehensive management. The remote sensing ecological index can objectively reflect the difference of spatial distribution characteristics of ecological environment in the four “Ecological+” governance regions. It can both objectively reflect the ecological status of the study area and reflect the differentiated spatial distribution characteristics of the ecological environment in different treatment areas, which is of long-term practical significance to the ecological construction of the study area. This study provides a theoretical reference for ecological assessment of complex situation under difficult site conditions.