Analysis Of Soil Environmental Changes Based On Remote Sensing In Western Mining Subsidence Area

The loess covered area is the key area for the development of coal resources in western China,the area is located in the loess plateau and its transition zone,the landform is complex and changeable,this area is arid and short of water,and the ecological environment of human settlement is fragile.Over the years,the large-scale underground coal mining has resulted in the surface subsidence,the surface crack,the collapse of the tableland,the depletion of groundwater and other mining damage.It has caused changes in soil moisture and vegetation on the ground and showed an increasing trend.It has a serious impact on green mining and safe mining in the western mining area.The growth of vegetation is closely related to soil moisture,both of which are important factors for environmental evolution in mining area.In order to study the impact of underground coal mining disturbance on vegetation,soil moisture and other environmental factors,this paper takes the Bin Chang mining area in Shaanxi as the research area based on the remote sensing data of the 2007-2017 years,selects the normalized vegetation index as the factor of the vegetation information,and builds the temperature vegetation drought index(TVDI)model by establishing the NDVI-TS characteristic space,and monitors and analyzes the change characteristics of the vegetation and soil moisture in mining subsidence area and non-mining affected area.The results show that NDVI has phonological periodic changes over the past 11 years and unimodal peaks occurre every year.The value of TVDI shows obvious changes in different seasons.In January,the temperature vegetation drought index is lower,that is,the soil moisture is larger.In July,the temperature vegetation drought index is higher,that is,the soil humidity is smaller.In order to analyze the disturbance effect of mining subsidence on the change of surface vegetation and soil moisture,the study area is divided into mining subsidence area 1,2 and adjacent non-mining affected areas A,B and C.The corresponding TVDI values of different regions are obtained respectively.The amalysis shows that the value of TVDI of thesubsidence area is different from that of the noo-mining affected area under the mining disturbance,the relative soil humidity in the mining subsidence area increases in January,and the relative soil humidity in the mining subsidence area decreases in July.In order to explore the mechanism of soil moisture change caused by mining subsidence,the depth and area of crack in the mining subsidence area are determined according to the subsidence range and damage degree of surface mining in 2007-2017 years.Due to the loose surface layer caused by surface cracks,the absorption and evaporation effect of surface water is aggravated,and the soil moisture in the subsidence area is higher than that in the non-mining affected area in the low temperature season in January.In the high temperature season in July,the evaporation degree of the subsidence area is higher than that in the non-mining affected area,and the relative soil moisture is lower than that in the non-mining affected area.This fully reflects the effect of coal mining subsidence on soil environment.The above research results are of guiding significance for land evaluation and environmental improvement in coal mining subsidence area in Western China.