| The study on the influence of the C hina’s rapid urbanization and urban characteristics changes on urban ecology environment is the impaortant basis for the sustainable development of C hina.Balanced urbanization development and urban ecological environment has become one of the important tasks of the country and the world for the sustainable urban developme nt.In recent years,quantitative and multidisciplinary research about the effects of urban expansion on urban eco-environment has been the consensus of scholars,and has become a hotspot in urban ecological research.Since 30 years o f reform and opening up,China has experienced rapid urbanization worldwide and its urban spatial characteristics and urban ecological environment have undergo ne tremendous changes.The heavy urban air pollution in C hina is one of the most prominent urban ecological environmental problems caused by human activities in urbanization.Therefore,based on urban ecology,remote sensing,GIS technology,spatial statistics and related mathematical statistics,the spatial and temporal evolution of urban expansion and urban air pollution,especially PM2.5 pollution in C hina,are studied in C hina.To explore and find the interaction mechanism between the urban expansion of China and urban spatial characteristics of changes and the urban air pollution.The main research methods and results are as follows:（1）Temporal and spatial distribution of PM2.5 concentration in C hina based on spatio-temporal geographic weighted regression modelIn this paper,we use the Geo graphic Temporal Weighted Regression（GTWR）to compute the aerosol vertical thickness（AO D）from different satellites,GEOS-Chem chemical transport simulation values and ground monitoring values to estimate the PM2.5 mass concentration.Spatial distribution and spatial-temporal evolution of PM2.5pollution in China from 1998 to 2015 were estimated,then temporal and spatial evolution of PM2.5 of each province were calculated and analyzed.The results show that the accuracy of the GTWR model is better than that of the GEOS-Chem chemical transport model.The accuracy of the estimation accuracy is 87.94%,which is 7.8%higher than that of the GEOS-Chem chemical transport model alone.the spatial distribution pattern of the PM2.5 mass concentration in C hina is a inverted"T"distribution pattern.The vertical pollution belt is“the three northeastern provinces-Beijing-Tianjin-Hebei-Shandong-Jiangsu,Henan,Anhui,Hubei,Hunan and Guangxi”as the zone in the southeast polluted region of C hina.The horizontal pollution belt is“North China Plain-Shanxi-Ningxia-Gansu-Xining-Xinjiang Taklamakan Desert”as the northwest regional pollution belt of China.The junction of the vertical and horizontal pollution belts is the North China Plain region.During 1998 to 2015,the PM2.5 pollution in C hina mainly intensified along the distribution pattern of the inverted"T"and spread to the surrounding areas,forming a stable four major pollution belts,Xinjiang Taklamakan Desert,N ingxia,Sichuan and Chongqing and the North C hina Plain.Of course,the most serious PM2.5 pollution is located in the North China Plain with the largest pollution area in C hina.In addition,C hina PM2.5annual average value change was analyzed:PM2.5 is soared from 29.89μg/m3in1999 to 39.49μg/m3in 2003 by 9.6μg/m3,the year average growth rate was 8.3%as the first growth stage;the second growth stage is soared from 34.76μg/m3in 2004increased to 38.82μg/m3in 2006 by the average annual growth rate of 5.84%;During2006 to 2012,PM2.5 was into a slowly mitigation stage,from 38.82μg/m3 in 2006slowed down to 33.02μg/m3 in 2012.During 2012 to 2015,the PM2.5 pollution has soared from 33.02 in 2012 to 38.49μg/m3in 2013 with an increase of 5.47μg/m3and growth rate of 16.57%per year.In 2013 China began to introduce a series of air pollution control policy,the PM2.5 mass concentration began to slowly slow down the state,from 2013 to 38.49μg/m3slowed to 35.99 in 2014,although by 2015 began to grow,but its growth rate（4.03%）is half of the previous growth rate（8.3%）.This indicates that although a series of air pollution control policies issued by C hina failed to control the PM2.5 pollution outbreak,it inhibited the growth rate of PM2.5 mass concentration,indicating that the relevant policies are still effective to control air pollution.（2）Spatial-temporal relationship between urban PM2.5 pollution and urban expansion in ChinaChina’s urban expansion is characterized by population expansion,urban regional expansion and economic expansion.The urban expansion in C hina is mainly distributed in the Yangtze River Delta,Beijing-Tianjin-Hebei,Pearl River Delta,Sichuan and C hongqing and other city groups.In summary,the speed and level of urbanization expansion in C hina are all regional,of which over 90%of the expansion area of the built-up area occurred in the eastern region,with the obvious distribution pattern of the east-west and the low-west,among which the Yangtze River Delta is the fastest growing.Since urban regional disaggregation data are only available for 2000and 2010,the calculation of urba n expansion and urban characteristics in C hina is based on the urban regional classification data for the two years.C hina’s urban built-up area in 2000 was 98819.88 km2,an increase of 126659.82 square kilometers in 2010,an increase of 27839.94 km2,an increase rate of 28.17%,the average annual growth rate of 2.82%.The study calculates the total urban population based on urban population density and urban area in China.Urban areas with more than 100,000urban population as typical representative area to analyze the urban environment effect caused by urban expansion and urban characteristic change in China.The total number of urban areas with a total population of more than 100,000people is 405,of which the built-up area in 2000 is 59210.24 km2,accounting for59.92%of the total built-up area in 2000,and the urban area The growth rate is43.51%,the average annual growth rate of 4.35%,is the national average annual growth rate of 1.54 times,the growth area of 25763.2 km2,the average annual growth rate of 1.57 times,Accounting for 92.54%of the growth area of built-up areas.405typical urban areas in 2000 the total population of 0.75 million people in 2010,the total population of 337 million people,the total number of 262 million people,an increase rate of 347.98%,an average annual increase of 34.8%.From t he perspective of population growth and distribution at the national scale and 405 typical urban areas,China has witnessed many changes in the population structure during this decade,in which the urban population mainly flows from the villages or small c ities into the 405typical metropolitan areas.The population density,night light index,impermeable surface coverage,vegetation coverage,normalized vegetation index（NDVI）,and vegetation cover are the main factors leading to the change of urban spatia l characteristics in the process of urbanization,regional expansion and rapid economic development.According to the spatial and temporal distribution of C hina N ight Light Index,the night light index of China in 2000 was 7.49%,and the national night light index increased to 11.05%in 2010,and the growth rate of night light index,the rate is47.53%,the average annual growth rate is 4.75%.Between 2000 and 2010,the population density in the 405 urban areas was 2.2 times that of the whole country,the water impermeable surface coverage was 3.31 times higher than that of the whole country.The vegetation coverage rate（NDVI）grew less than the national level,and the nighttime light index was 2.4 times that of the whole country.While the same spatial pattern,China’s average PM2.5 concentration increased from 32.10μg/m3in2000 to 37.54μg/m3in 2010 with an increase of 5.42μg/m3and an average annual growth rate of 1.63%.The PM2.5 concentration in 405 urban areas increased from28.99μg/m3to 53.51μg/m3in 2010,with an increase of 24.52μg/m3.The average annual growth rate was 8.46%,5.19 times of the national average.In addition,the PM2.5 concentration is partly due to dust and sea salt,especially in northwest C hina,such as the Taklimakan Desert in Xinjiang,etc.,dust and sea salt is not the result of urbanization.Therefore,the spatial and temporal distribution of PM2.5 pollution in China was analyzed and analyzed.The average mass concentration increased from24.90μg/m3in 2000 to 30.39μg/m3in 2010,and the growth value was 5.49μg/m3.The average annual growth rate of 2.20%,while 405 urban areas to the dust to the sea salt of PM2.5 mass mean value from 24.64μg/m3in 2000 increased to 47.39μg/m3in2010,the growth value of 22.75μg/m3,year The average growth rate of 9.23%,4.20times the national average.The results show that in 2000,the average concentration of PM2.5 in typical urban areas was lower than the average level in C hina.The air pollution in rural areas of C hina was serious in urban areas,mainly because in 2000 the rural living standard was backward.Rice and heating,and the majority of rural farming,serious biomass burning is the main reason leading to the increase in the concentration of PM2.5concentration in rural areas,rural roads are dirt roads,will form a serious dust pollution,resulting in PM2.5 concentration high.The emission of the main sources of motor vehicles and industrial sources of emissions in 2000 are not prominent,resulting in the 2000 PM2.5 concentration higher than urban areas.With the advance of urbanization in C hina,urban air pollution in China is becoming more and more serious,the rural air has become better,with the reduction of farming population,biomass burning,rural people have begun to use natural gas cooking and heating,thereby reducing PM2.5 pollution in rural areas.The city’s motor vehicle growth and heavy industry,the burning of chemical fuels,leading to urban air pollution is more serious.And China with the huge population moving from rural to urban areas,the limited urban space carries more and more people’s living needs,leading to deterioration of the urban ecological environment and serious increase of air pollution.From this conclusion,it is concluded that the process of urbanization in China is the main factor leading to the serious urban pollution in C hina from the source of pollution,excluding the diffusion and dilution of meteorological conditions.China’s urban expansion is in line with"Hu Huan yong line"distribution pattern.Taking Hu Huanyong Line as the boundary,5.93%（24/405）of 405 typical urban areas are located in the northwest and 94.07%（381/405）are located in the southeast of China.The urban area of northwest C hina in 2000 accounted for 2614.14 km2,which increased to 3550.93 km2 in 2010,the urban expansion area was 936.80km2,with average annual growth rate was 3.58%.The total population of the typical urban areas in Northwest C hina has increased from 42.607 million in 2000 to 13.6333million in 2010,with an average annual growth rate of 21.97%.The spatial characteristics of the typical urban areas in Northwest China showed that the area-weighted population density increased by 2119.22 person/km2,An area-weighted opacity increase of 8.06%,an area-weighted night light index of34.67%,and an area-weighted vegetation index of 0.05.The PM2.5 concentration in the urban area of Northwest China increased from 21.43μg/m3in 2000 to 48.15μg/m3in 2010,with an increase of 26.72μg/m3and a growth rate of 124.69%The average growth rate of PM2.5 area in typical cities in Northwest C hina increased from8.08μg/m3in 2000 to 23.99μg/m3in 2010,with the average growth rate of 12.47%.In addition,after removal of dust and sea salt components,the average value of PM2.5weighted average concentration 15.91μg/m3,the growth rate of 196.91%,the average growth rate of 19.7%.It can be seen that PM2.5 is mainly caused by dust in northwest C hina.In 2000,the proportion of PM2.5 mass concentration in typical urban area of Northwest C hina was 62.3%μg/m3,and in 2010,the proportion of dust component The proportion of50.18%,dust composition has been reduced,but PM2.5 pollution in the overall growth,it is because the northwest urbanization caused by pollution components in the growth.The average annual growth rate of PM2.5 after removal of dust and sea salt was significantly higher than that of PM2.5 containing all components,that is,the growth of PM2.5 produced by urbanization was significant,and the dust produced by environment Such as change is not significant.It is concluded that the main factor leading to the increase of PM2.5 concentration in the northwest area is the pollution discharge in the process of urbanization.And the urban area of 94.07%（381/405）east of Hu Huanyong line increased from 56596.10km2 in 2000 to 81422.51km2 in 2010,and the urban expansion area is 24826.41km2,which is the area of urban expansion in Northwest C hina 26.50 times the eastern area of the city’s average annual expansion rate of 4.37%.The total population of the eastern city increased from 71 million in2000 to 323 million in 2010,with a population growth of 262 million,18.71 times of the population growth in the northwest and an average annual growth rate of 36.9%.In addition,the urban spatial characteristics of typical urban areas in eastern China are as follows:the area-weighted population density increases by 2777.29person/km2,which is 658.07 person/km2 higher than that of northwest C hina,and the area-weighted impervious surface coverage increases The area-weighted NDVI increased by 0.20,which was four times as much as that in the northwest urban area.The area-weighted NDVI increased by 0.20 times,and the area-weighted night light has increased by 39.58%,16.73%and 2.08 times,respectively,compared with the northwest region.The PM2.5 area weighted mass concentration increased from 14.58μg/m3in 2000 to 54.63μg/m3in 2010,with the development of urbanization in the eastern cities,accompanied by more severe PM2.5 pollution.The average annual growth rate is 27.47%,which is 129.29%times of the growth rate of PM2.5concentration in typical cities in northwest China.In addition,the PM2.5 mass concentration increased from 12.86μg/m3in 2000 to 50.03μg/m3in 2010,a nd the mass concentration of PM2.5 increased by 37.17μg/m3in the eastern city area,With an average annual growth rate of 28.9%,9.2 times higher than the average annual growth rate of the western region.In addition,urbanization in eastern C hina was significantly higher than that in the northwest cities,and the PM2.5 pollution level in eastern C hina was lower than that in northwest C hina in 2000,mainly due to the pollution caused by the urbanization in eastern China in 2000 The PM2.5 pollution caused by the city is not reflected,and the PM2.5 concentration in the northwest urban area is higher than that in the eastern city due to the perennial sand and dust.By 2010,the intense urbanization process in eastern China,with the increase of automobile exhaust emissions and the increase of industrial pollution,make the PM2.5 pollution caused by the urban process become the dominant factor,the PM2.5 pollution in the eastern cities in 2010 is far away Higher than the northwest city.（3）The effect of urban expansion and urban characteristic change on PM2.5concentration in ChinaIn order to analyze the impact of C hina’s rapid urbanization process on urban air pollution in China,this study,based on the data of urban expansion and urban spatial variability in 2010 and 2000,univariate regression analysis was used to analyze the correlation between spatial variability and PM2.5 mass concentration.The results showed that the relationships between urban expansion and spatial change and PM2.5mass concentration are as follows:nighttime light index>urban compactness>population density>ISC>urban area expansion>urban population expansion>NDVI;The relationship between nighttime light index and PM2.5 is the most obvious,with the correlation coefficient R is 0.76,showing that the impact of China’s economic development on PM2.5 concentration is the most significant.The correlation coefficients of urban spatial compactness and population density change with PM2.5mass concentration are 0.65 and 0.54,respectively.The correlation between the intensity of the water impermeable surface,the expansion of urban area and the expansion of urban population were related to PM2.5,the correlation coefficients are0.38,0.37 and 0.28,respectively.The correlation between N DVI and PM2.5concentration was relatively small,with R=0.16.The results show that the relationship between urban characteristic change and PM2.5 mass concentration is larger than urban expansion（population expansion,urban area expansion）.From the relationship between the univariate change and PM2.5 concentration variation,the correlation between urban characteristic change and urban spatial heterogeneity change is higher than urban expansion index（population expansion,geographical area expansion）,especially the change of urban spatial features.Therefore,in the future,rational distribution of urban spatial pattern will not produce pollution,but also reduce pollution emissions,bring an important way for urban air pollution control and prevention.In order to further analyze the effects of urban expansion and urban spatial characteristics on urban air pollution,the multiple regression model was used to analyze the effect of urban expansion and urban characteristics on urban PM2.5concentration.The problem of urban air pollution is not only the result of urbanization expansion,but also affected by urban topography,urban meteorological conditions,biomass burning and other factors.Therefore,in the model construction process,the urban basic characteristics（built-up area,total population,compactness,population density,night light index,impervious surface coverage,NDVI）,urban meteorological conditions（rainfall,air temperature）,urban topography（elevation,slope,aspect）,biomass burning and other factors on urban PM2.5 pollution,these spatial variables are added to the model,as adjustment parameters,in order to more accurately analyze C hina urbanization process,urban expansion,changes in urban characteristics,urban spatial heterogeneity of the impact of changes in PM2.5pollution.Based on these influencing factors,this study constructed a multivariate regression model containing 24 independent variables and a stepwise multiple regression model with partial variables.The results show that the multiple regression model including urban expansion,urban characteristic change,urban characteristic heterogeneity and adjustment parameters（2000 base urban characteristics,meteorological conditions,urban terrain,straw burning）can analyze the PM2.5concentration change of 77.8%and the change of city characteristic is the strongest,which can resolve the change of PM2.5 mass concentration.The variation of urban characteristic spatial heterogeneity is 14.9%,and the variation of urban characteristic is 14.9%（3.7%）.The results show that the urban expansion,urban characteristic change（urban compactness,urban impervious surface coverage,vegetation coverage,night light index,urban light intensity index,urban light intensity index,Population density）and the spatial heterogeneity of urban characteristics have a significant effect on PM2.5 mass concentration.In the future sustainable development of new urban construction,the pattern and policy of urban land use are very important for the construction of environment-friendly and ecologically harmonious cities.With the multivariate regression model,we have analysized the relationship between urban expansion and characteristics changes and PM2.5 concentration among China’s cities.Taking the 2000 baseline characteristics,urban terrain,straw combustion and meteorological condition as the adjustment variables,the multivariate regression model can explain the 77.8%of the change in PM2.5.The change in urban characteristics had a greater impact on PM2.5 change than 2000 baseline characteristics.It is concluded that C hina’s urban expansion,city characteristics change（city compactness,impervious surface coverage,vegetation coverage,night lighting index,population density）and the spatial heterogeneity of the urban characteristics has significant effects on PM2.5 change,suggesting urban design and land use policies can have substantial impacts on local air pollution levels.Thus,the future sustainable development of the New-Type urban construction,urban land use pattern and policies on the construction of environment friendly,ecological and harmonious cities have very important significance. |
PDF Full Text Request