Process analysis of land destruction and reclamation in coal mining areas using ecological risk assessment

With the development of coal mining and land reclamation, the landforms and environmental conditions in mining areas have been disturbed. It is necessary to take positive initiatives to prevent eco-risks during mining exploitations and construct a key ecological civilization and socio-economic development. This paper used Pingshuo Coal Mine in Shanxi Province as a case study to analyze and build an evaluation model of dynamic ecological risks in coal mining areas. Using 30 m×30 m grid units, the study evaluated, mapped and classified at unit grid scale ecological risks in the mining area. Based on the study, the ecological risk in the mining area varied with land destruction and reclamation processes. A model of the cumulative effect of land destruction was used to assess risk sources. Also remote-sensing images and field measured data were used to calculate the values of ecological vulnerability index in the region. Through index calculations, the ecological risk values for the mining area were determined for 2001 and 2010. Also through the combination of existing remote-sensing techniques with field measurements, the values were reasonably up-scaled for the entire area with a highly visualized evaluation results. Then the effects of potential risks were determined and optimized land use forms and mining technology identified using the dynamic changes in ecological risk. The results showed that with increasing coal production, the cumulative affecting area of land destruction increased by 7 095.17 hm² from 2001 to 2010. However, the cumulative effect decreased obviously for reclaimed dumps. With the continuous eastward open-pit mining, the effect of mining on the west region of the study area weakened. After 10 years of land reclamation and ecological reconstruction, ecological risks in reclaimed dumps declined and the ecosystem seemly stabilized. The medium and low risk area accounted for 0.02% of the disturbed area due to mining in 2001 and up to 16.77% in 2010. This implied that land reclamation reduced the effects of ecological risk in the region. The combined risk value for open-cast and underground mining was unstable, with a value of ecological risk as low as 0.45 or as high as 0.80. The risk of partial uneven subsidence and soil erosion clearly increased in frequency and intensity in the area. The study demonstrated that the analysis of ecological risk could reflect the processes of land destruction and reclamation via mining, changes in ecosystem structure and function, and the spatial heterogeneity in space-time fabric. Hence such analysis was a reference base for planning environment recovery and regional development. As a source of risk for the regional ecosystem, land reclamation in mining areas should focus on increasing the ecological functions of reclaimed areas.