| In recent years,the yield of mineral resources increased sharply along with the rapid development of our economy,which generated a series of environment questions,such as the decline of groundwater level under mining area,the reduction of surface runoff and soil drought in mining area,and exacerbated fragile ecological environment.Therefore,it is particularly critical to minimize the damage of ecological environment in the mining area during the process of mining exploration.For this purpose,the real-time and accurate monitoring of evolutionary process of surface moisture and vegetation in mining area,and discovering the influence rules of mining activities on ecological environment become crucial for protecting ecological environment of mining area.Remote sensing is fast and timely,which also possesses multi-temporal,multi-spectral and multi-resolution,and can effectively monitor the surface change information for large areas and has become an important means for monitoring surface environment.Taking Liaoning Mining Development Central Zone as research area,this paper studied out a mining area soil moisture inversion algorithm through combining the ground-based microwave observation experiments with microwave remote sensing theory.Moreover,based on this and comprehensive utilization of satellite remote sensing microwave brightness temperature data,GIMMS NDVI 3g data and meteorological data,this paper analyzed the space-time evolution characteristics of soil moisture,surface drought and NDVI of Liaoning Mining Development Central Zone,revealed the interactional relationships between vegetation restoration and soil moisture in mining area,and made an overall estimation on the vegetation restoration and soil moisture conditions from 1979 to 2015 of the researched,which provided observation data and technical support for the sustainable development of Liaoning Mining Development Central Zone.The main tasks of this paper are summarized as follows:(1)Demonstrated the microwave radiation brightness temperatures of vegetation had dual dependence on the direction and LAI after quantitatively analyzing the corresponding relationships between surface roughness and microwave radiation brightness temperatures through multiband microwave radiation ground-based experiments;proposed that prior surface roughness and vegetation row structure information could help to reduce the uncertainty of soil moisture inversion.The results showed that there was a linear relationship between soil moisture and soil microwave emissivity.The MPDI and microwave emissivity polarization difference had a quadratic curve relation with soil roughness,and the correlation of C band was superior to that of Ku band.(2)Inversed the time series surface soil moisture data set which covered Liaoning Mining Development Central Zone through the abovementioned algorithm,based on the ground-based microwave remote sensing observation experiments,the comprehensive influence of surface roughness and vegetation canopy,and long serial multisource passive microwave remote sensing brightness temperature data.The results showed that the soil moisture of Liaoning Mining Development Central Zone had a spatial distribution characteristic presented as eastern-high and western-low,with declining annual average soil moisture and accompanying by a change cycle of 10 and 20 years.The average soil moistures in the spring,summer,autumn and winter were 0.207cm3/cm3,0.237cm3/cm3,0.229cm3/cm3 and 0.205cm3/cm3 respectively.The soil moistures in summer and autumn were slightly higher than those in winter and spring.The soil moistures in spring and summer had increasing trends,and the increase of soil moisture in summer was about 5 times than that in spring;the soil moistures in autumn and winter had decreasing trends,and the decrease of soil moisture in winter was about 3 times than that in autumn.(3)The immediate result of surface soil moisture changes is drought.Therefore,in order to effectively evaluate the space-time variation characteristics of drought,a SWDI-based remote sensing drought monitoring method was put forward under the background of climate change and typical features of mine soils,which effectively resolved the seasonal differences between soil properties and drought.On this basis,the segmenting and zoning remote sensing monitoring of drought in mining area in different space-time was achieved.Through statistically analyzing the SWDI average values and trends from March to October from the year of 1979 to 2014,it was found that the September and October were drought-stricken months,and showed strong trends of continuous drying,which were important months with higher drought risks.Compared with the previous period,SWDI in Chaoyang Coal Mine decreased relatively after 2000,showing a drying trend;the SWDI of other three mining areas(Fuxin Coal Mine,Anshan Iron Mine and Benxi Iron Mine)increased relatively,showing a wetting trend.(4)Based on the GIMMS NDVI 3g data set from 1981 to 2015 and medium resolution Landsat series remote sensing satellite image data of researched area,and after collecting meteorological data and analyzing interactive relationships between vegetation change and meteorological factors,it was revealed that the NDVI of Liaoning Mining Development Central Zone showed a spatial distribution feature presented as western low and eastern high among 34 years.According to the analysis results of NDVI variation trends from April to October in four mining areas,the NDVIs of Fuxin Coal Mine and Anshan Iron Mine showed significantly increasing trends;the NDVI of Chaoyang Iron Mine showed a dramatically decreasing trend;the NDVI of Benxi Iron Mine did not varied much.(5)Thoroughly analyzed the main driving factors(including mining intensity,soil remediation,greening,well water reutilization,etc.)which led to the mining area environment changes,and revealed the positive and negative feedback relationships between groundwater and soil moisture,and between soil moisture and vegetation,based on the space-time evolution characteristics of soil moisture,surface drought and NDVI in four typical mining areas(Chaoyang,Fuxin,Anshan and Benxi).The results showed that Chaoyang Coal Mine had a production drawdown since 2000 but became drought due to few ecological restoration measures;Fuxin Coal Mine had a dramatically production decline since 2000,but strengthened the efforts to ecological restoration,which became wetting;Anshan Iron Mine and Benxi Iron Mine had great yield increase in recent years,but carried out effective ecological rehabilitation measures,which had trends of wetting.The differences of ecological changes in abovementioned four mining areas presented that the soil and vegetation restoration measures carried out in mining area can effectively relieve ecological environment degradation in mining area,and even improve the ecological environment of mining area. |
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