Groundwater Environmental Response In The Urbanization Process Of Nanchang City

Nanchang,located on the shore of Poyang lake,is a typical demonstration city in the national ecological civilization experimental area?jiangxi?and the ecological environment is relatively weak.In recent years,the urbanization level of Nanchang city develops rapidly,which is manifested by the continuous growth of urban population and economy,as well as the constant changes in land use morphology,structure and function with the rapid development of urbanization.And excessive levels of nitrogen and phosphorus in the shallow groundwater of poyang lake economic zone have occurred frequently,as well as the frequent occurrence of water quality deterioration,soil erosion,regional geological disasters and other environmental problems.Therefore,it is of great significance to explore the spatio-temporal interaction between land use and groundwater environment in Nanchang city under the rapid urbanization.In this paper,mathematical statistics method,intensity analysis method and comprehensive evaluation index method are used to explore the spatio-temporal dynamic changes of urbanization,land use and groundwater pollutants in Nanchang city.Then,STIRPAT model is used to discuss the driving factors of urban expansion in the process of land use change.Based on GIS spatial statistics,combined with clustering analysis,LSD multiple tests were used to analyze the spatial changes of groundwater quality under different land use types.Population,economy,space,society and ecological urbanization rate were used to conduct EKC test on groundwater to analyze the evolution law of groundwater quality with urbanization in the past 16 years.The main conclusions are as follows:?1?the comprehensive score of urbanization in Nanchang city has gone through three stages.The score rose steadily,then experienced a relatively flat increase,and next entered a relatively rapid increase.On the whole,Nanchang's urbanization process is progressing smoothly.From the perspective of land use change intensity,the land use change intensity of Nanchang gradually increased after 2000.The increasing intensity and decreasing intensity of build-up land and unused land are both active.The increase intensity and decrease intensity of cropland land were both stable,while the increase intensity and decrease intensity of other land types were different.The increase of build-up land mainly comes from cropland land,and the decrease of cultivated land is mainly converted into construction land.The quaternary groundwater quality experienced a trend of deterioration and then rise between 2001 to 2015.The better water quality area is mainly distributed in nangang plate spring workshop,provincial academy of agricultural sciences and water tank factory.?2?Nanchang land use change underwent the drives of natural condition,economy,population,government policy,economy development was the first driving force of urban expansion.Based on the clustering analysis of different water quality indexes and multiple tests of LSD,it was found that the spatial differences of anions such as Na⁺,Ca²⁺,Mg²⁺,Cl^-,HCO₃^-and SO₄^2-were less affected by the heterogeneity of land use,while the nutrient index was more affected by the heterogeneity of land use.?3?According to the regression results of comprehensive urbanization rate and groundwater quality,EKC curve shows an"inverted U"trend in 15 years.With the improvement of urbanization level,groundwater quality deteriorates and then gradually improves.Among them,the regression curves of population,economy,society,space and ecological urbanization and groundwater quality all show an"inverted U"trend.The evaluation coefficient F value of ecological urbanization and groundwater quality is still in the rising stage of"inverted U"curve in 15 years,and has not reached the inflection point of improvement,it shows that the current ecological urbanization of Nanchang city haven't arrive at the optimal level.