Research On Monitoring The Spatial-temporal Evolution Of The Surface Environment In The Huinong Coal Mining Subsidence Area Based On Multi-source Remote Sensing

The exploitation of coal resources has made a huge contribution to China’s economic development,but it has also caused serious damage to the ecological environment in mining areas.Therefore,it is particularly important to monitor the surface environmental problems caused by coal mining in a real-time,accurate and effective way.In this paper,the surface environment of Huinong coal mining subsidence area in Shizuishan City,Ningxia is taken as the research object.Firstly,based on the collected data and field investigation,the geological environment conditions and the general situation of coal mining in the study area are analyzed,the main mine geological environment problems are clarified.And the five-phase remote sensing data from different sources are preprocessed.Secondly,combining the results of field survey,comparative analysis of measured spectral curves,water quality analysis and image feature analysis,the interpretation signs of surface environmental elements in the coal mining subsidence areas were established and research on two information extraction methods based on object-oriented and hyperspectral remote sensing was carried out.Finally,the corrected interpretation results of remote sensing images with different phases are superimposed and analyzed to realize the monitoring of spatial and temporal evolution of the surface environment in the coal mining subsidence area.The results of the study are as follows:(1)PCA,NNDiffuse Pan Sharpening,Gram-Schmidt and Brovey Sharpening are used to fuse the remote sensing images of QuickBird,WorldView-2 and GF-2 in the study area.It is shown that:The fusion result of QuickBird is the best by use of GS method while the fusion results of World View-2 and Gaofen-2 are the best by use of PC A method.In addition,the GF-5 hyperspectral data were preprocessed by bad band elimination,wavelength information writing,radiation correction and geometric correction,and the basic data meeting the accuracy requirements were obtained.(2)Through the field investigation,sampling and spectral curve measurement,the field characteristics,spectral characteristics and remote sensing image characteristics of various environmental elements were analyzed,and the interpretation signs of typical features in coal mining subsidence areas,such as badlands,coal gangue,coal heaps,cultivated land,other construction,residential areas,vegetation cover areas,and water bodies were established.(3)The research on the extraction method of surface environment information in coal mining subsidence area based on object-oriented method shows that the overall accuracy(73.8%)and kappa coefficient(0.657)of random forest classification are slightly better than those of CART classification(72.8%,0.641).Combined with the field survey to correct the four-temporal random forest classification results,the classification accuracy was greatly improved,and the overall average accuracy of the obtained surface environmental elements interpretation map was 89.3%,with an average kappa coefficient of 0.872.(4)The spectral angle matching information extraction method based on hyperspectral data obtained that:the vegetation in the Huinong coal mining subsidence area is mainly trees and shrubs,supplemented by grasses;mine pit water is mainly distributed near the mine collapse pit,with an area of 0.392km2,other surface water is mainly artificial reservoirs;bare soil is widely distributed,accounting for 21.5%of the total area of the study area,while coal gangue,loose gravel and coal fly ash,which is mainly distributed around the coal mine buildings,with a small area.(5)The overlay analysis of four-phase interpretation map of surface environmental factors in the study area can be concluded:From 1979 to 2003,the area of cultivated land and vegetation cover decreased sharply,and the conversion to badlands and residential areas was particularly obvious,which was mainly caused by the infrastructure construction and soil erosion in the process of urbanization.Coal heaps,water bodies,and coal gangue exhibited a trend of rapid growth,mainly converted from badlands,indicating that Mining activities have caused severe damage to the environment of the mining area.From 2003 to 2018,the vegetation-covered area exhibited the fastest growth rate,while the area of coal gangue and badlands significantly reduced.After more than 10 years of mine geological environment renovation,the surface environment of the coal mining subsidence area greatly improved,and the hidden dangers of geological disasters such as ground subsidence and ground fissures have been basically eliminated.The surface environment before and after the renovation of the mine geological environment in the study area is consistent with the results of remote sensing monitoring.