Research On The Comprehensive Evaluation Of The Ecological Environment Quality Of Tongchuan City Based On Landsat TM/OLI Data

Ecological environment is closely related to human activities.It provides more abundant natural resources,living space and material conditions,which is the basis and guarantee for the survival and development of human society.The regional eco-environmental conditions influence even determines the socio-economic development and the quality of life of the people.The ecological environment has become one of the most important issues that experts and scholars at home and abroad pay attention to.As an important resource-based city in Shaanxi Province,Tongchuan City has long-term over-exploitation of mineral resources and outstanding ecological and environmental problems.In 2009,Tongchuan City was identified as a resource-exhausted city by the state and began the industrial transformation and upgrading.Under the deployment of national ecological civilization construction,in order to achieve the coordinated and sustainable development of regional social economy and natural environment,it is necessary to make a scientific,reasonable and objective evaluation of its ecological environmental condition.Taking Tongchuan City as the research area,the Landsat TM/OLI remote sensing images of 2002,2009 and 2016 were selected,and the comprehensive evaluation index of ecological environment was constructed by combining the evaluation indexes listed in the Technical Specification for the Assessment of Ecological Environment Status promulgated by the Ministry of Environmental Protection in 2015 with the remote sensing ecological indexes.The comprehensive evaluation and result analysis of ecological environment status of Tongchuan City was carried out by using 500m*500m grid as a unit.Conclusions are drawn as follows:(1)The ecological environment quality of Tongchuan city has been improved during the research period.In 2002,2009 and 2016,the average values of comprehensive evaluation index were 0.60,0.59 and 0.62 respectively.The transformation and development had a significant effect on the improvement of ecological environment quality in Tongchuan.The ecological environment quality of Yijun County and Yaozhou District is better than that of Wangyi District and Yintai District.Especially,the ecological environment quality of Wangyi District has declined significantly in the past 14 years.(2)From 2002 to 2016,the ecological environment quality of Tongchuan City was generally good.In 2002,the area of ecological environment in each grade was general>good>excellent>discrepancy>poor.In 2009 and 2016,it was excellent>good>general>discrepancy>poor.Grade change as a whole showed "four minus one increase",that is,the area of poor,discrepancy,general and good grades decreased,while the area of excellent grade increased significantly.The "excellent" grade areas are mainly located in the northwest of the study area,the Ziwuling Mountains,and the middle and eastern regions with higher terrain."good" grade area mainly distributes near the river system and terraces on both sides of the valley."general" grade is mostly distributed at the edge of woodland and some small ditches and slopes.The "discrepancy" and "poor" grades are mainly distributed in the south and northeast of Tongchuan City.(3)With the help of red,yellow and green detection method,Tongchuan’s eco-environmental quality has improved in the past 14 years,and the area where the eco-environment has not changed significantly is larger than that of the deteriorated area.The areas of improvement,no obvious change and deterioration accounted for 58.69%,35.09%and 6.22%of the total area,respectively.The areas with improved ecological environment cover the west,northwest and part of the south of Tongchuan City;the deteriorating areas mainly distribute in the south,southeast and northeast of Tongchuan City with relatively flat terrain,mostly in massive or sporadic shape;the areas without obvious changes distribute widely,except in the northwest.(4)Among the influencing factors of Tongchuan’s ecological environment quality,there is a significant correlation between elevation,slope and ecological enviroument quality.The higher the elevation,the better the ecological environment quality;with the increase of slope,the overall ecological environment quality has been improved.Mineral resources are highly concentrated and the ecological environment quality is relatively poor.The correlation degree between landscape diversity index and ecological environment quality is low.The order of ecological environment quality of land use types from high to low is forest land>grassland>water area>unused land>cultivated land>construction land.