Spatial-temporal Pattern And Driving Factors Of Wastewater Discharge In Yangtze River Economic Zone

Since the reform and opening-up policy,China’s economy has been growing rapidly.But this development model of "paying attention to efficiency and neglecting quality" brings a series of resource and environmental problems.The issues of environment,resource utilization and sustainable development are gradually becoming major challenges for social development.Water resources security is the basic guarantee for people’s own health and sustainable development of economy,society and ecological environment second only to food and food safety.Therefore,water pollution has become one of the current major concerns.As the longest river in China,the Yangtze River plays an important ecological function.With the introduction of the "Yangtze River Economic Zone Strategy",it is emphasized that the development of the Yangtze River Economic Zone will be promoted with the core concept of "ecological priority and green development".How to improve the water environment of the Yangtze River,control wastewater discharge,strengthen wastewater treatment,and achieve spatial matching and coordinated development of economic and social factors and resource and environment ecological elements have become issues that must be considered at present.Therefore,this study used Exploratory Spatial Data Analysis(ESDA)to explore the temporal and spatial evolution characteristics of industrial wastewater discharge,domestic sewage discharge and total wastewater discharge in the Yangtze River Economic Zone from 2002 to 2016.And the Logarithmic MeanDivisia Index(LMDI)is used to decompose and analyze the driving factors of industrial wastewater discharge,domestic sewage discharge and total wastewater discharge.The main conclusions are as follows:(1)In terms of the time evolution,the industrial wastewater discharge and total wastewater discharge in the Yangtze River Economic Zone increased first and then decreased after reaching the peak in 2005.Showed an inverted “U” curve from 2002 to 2016.The discharge of domestic sewage from residents is on a volatility.(2)In terms of the spatial distribution,overall,the industrial wastewater discharge and total wastewater discharge increased from upstream to downstream from 2002 to 2016 in Yangtze River Economic Zone,and the domestic sewage discharge was relatively scattered with no obvious accumulation areas.In the emission pattern,for industrial wastewater,cities with high discharge and medium discharge have decreased,and cities with low discharge have increased.For domestic sewage,cities with high discharge and medium-low discharge have increased,and cities with low discharge have decreased.For total wastewater,cities with high discharge have decreased,cities with medium-low discharge and low discharge have increased.In the trend of change,industrial wastewater discharge firstly migrated from the downstream to the middle and upper reaches,spread from large cities to small and medium-sized cities,and then the discharge in the Yangtze River Economic Zone decreased sharply.The domestic sewage discharge in municipalities and major capital cities increased.The total wastewater discharged gradually shifted from the downstream to the middle and upper reaches.(3)In terms of the spatial relationship,the industrial wastewater discharge and total wastewater discharge in the Yangtze River Economic Zone show a clear spatial agglomeration,but the domestic sewage discharge is in a discrete state in the distribution of space,without significant agglomeration characteristics from 2002 to 2016.(4)In terms of the driving factors,Technical improvement effect has a strong inhibitory effect on wastewater discharge.The contribution of industrial structure to wastewater discharge will change according to the policy change.If the policy emphasizes the development of the secondary industry,industrialwastewater discharge increases.If the policy attaches importance to the development of the tertiary industry,the domestic sewage will increase,and vice versa.The economic development effect is the main factor leading to the increase in the discharge of industrial wastewater,domestic sewage and total wastewater.The population effect will result in an increase in wastewater discharge,but the amount is small and the impact is not significant.