Spatio-temporal Variations of Nitrogen Dioxide Pollution in China, 2005-2015

• Other Authors: Cui, Yuanzheng (author.)
• Format: Others
• Language: English; Chinese
• Published: 2016
• Online Access: http://repository.lib.cuhk.edu.hk/en/item/cuhk-1292400

近年來，伴隨著快速的城市化與工業化，中國的經濟經歷了前所未有的迅猛增長。但也因此帶來了諸如二氧化氮（NO2）污染等很多環境問題。二氧化氮作為大氣中主要污染物之一，在對流層化學中起著十分重要的作用。本論文主要研究由中國政府在經濟和環境政策上的區域發展差異所導致的二氧化氮污染在時間和空間尺度上的變化差異和特點。研究結果對未來的控制排放政策制定具有重要的參考價值。 === 該論文研究的主要目的是通過分析星載臭氧監測儀（OMI）獲取的2005年到2015年NO2垂直柱濃度（VCD）的資料，研究中國地區對流層中的二氧化氮污染在空間和時間上的變化趨勢。研究表明，中國污染最嚴重地區的對流層NO2柱濃度自2005年開始迅速上升， 2011年左右達到峰值，此後逐漸下降。到2015年，中國東部的部分地區對流層二氧化氮污染狀況有所緩解，已恢復至2005年的水準。同時發現，NO2污染已從傳統的中國東部高度發達的地區擴展到西部地區的新興城市群。另外，通過將衛星資料獲取的結果與GEOS-Chem模型模擬得到的2005-2012年資料進行比較，證實了衛星觀察到的NO2變化趨勢主要是由人為排放變化的因素所導致。 === 本文進一步採用小波分解方法對中國西部省份2005 至 2013期間的NO2進行長期趨勢的提取分析。通過分析發現，2005年到2013年間，中國西部人為NO2年增長率達到了8.6±0.9％yr-1，特別是中國西北地方，其NO2柱濃度的增長率高達11.3±1.0％yr-1，超過了中國西南地區（5.9±0.6％yr-1）和中國東部的重要地區（其中京津冀地區5.3±0.8％yr-1，長江三角洲4.0±0.6％yr-1以及珠江三角洲-3.3±0.3％yr-1）。通過對社會經濟的分析表明，中國西北地方NO2的快速增長與中國政府所實施的“西部大開發”政策，當地相對較弱的排放控制監管力度以及當地快速發展的污染密集型產業緊密相關。 === 利用高分辨率NO2 VCD的資料集（0.125°×0.125°空間分辨率），採用三個定量指標（“面積相對趨勢”作為城市面積的擴大指標，“濃度相對趨勢”作為城市污染面積的濃度值，“最大值相對趨勢”作為峰值強度）來分析2005至2015年間中國地級市的城市污染狀況。此外，通過將2010年NO2的年均濃度的空間分佈與夜晚燈光和人口密度數據進行比較發現NO2數據和夜晚燈光和人口密度具有相似的空間格局：其中NO2與夜晚燈光相關性為0.74， 與人口密度相關性為0.66。這凸顯了城市化的結果和污染對健康的影響。最後，我們採用時空地理加權回歸（GTWR）模型探索基於城市層面2005 - 2013年NO2污染與GDP之間的時空關係。該模型結果表明，中國內陸的一些欠發達城市具有相對較高的正係數。對於大多數中國城市，基於單位GDP的NO2污染強度有所下降逐年下降，其結果反映了污染物控制排放政策在近些年取得了一定程度的進展，同時也伴隨著東部地區部分產業向西部轉移，發達地區向欠發達地區轉移。 === 研究結果表明，要實現更為均衡的區域發展，中央和地方政府應該高度重視現存在的不平等的區域經濟和環境政策所呈現的空間異質性，進一步優化能源結構以及完善生態補償機制。除了在東部地區繼續緩解氮氧化物等污染物的排放同時，更應加大控制中國西部地區的排放力度，以達到所有地區環境可持續發展的目標。 === China has experienced rapid economic growth in recent decades, accompanied with intensive urbanization and industrialization. This economic growth has led to many significant environmental problems, including deteriorating nitrogen dioxide (NO2) pollution. NO2 is a key air pollutant, and it plays a major role in the tropospheric chemistry. This thesis investigates the extent to which the characteristics of NO2 pollution changes at different spatial and temporal scales reflects regional inequality in economic and environmental policies enforced by Chinese governments, which has important implications for future emission control. === The objective of this thesis is to investigate the spatial and temporal variability and trends of tropospheric NO2 pollution over China, by analyzing the NO2 vertical column density (VCD) data over 2005 to 2015 retrieved from the space-borne Ozone Monitoring Instrument (OMI). It is found that over most polluted regions in China, the NO2 columns increased rapidly since 2005, reached their peaks around 2011, and started to decline afterwards. Over parts of Eastern China, the NO2 levels in 2015 were close to the levels in 2005. Furthermore, severe pollution has extended from the traditional highly developed regions in Eastern China to newly emerged cities clusters in the west. Further comparisons with GEOS-Chem model simulations for 2005-2012 confirm that the OMI observed NO2 trends were driven mainly by changes in anthropogenic emissions. === Then the long-term trends of NO2 over 2005–2013 from other scales of temporal variability over provincial-level regions of Western China were further distinguished, by using a wavelet decomposition analysis. The anthropogenic NO2 grew rapidly over Western China at a regional average rate of 8.6 ± 0.9% yr-1 between 2005 and 2013. The rate of NO2 growth during 2005–2013 reached 11.3 ± 1.0% yr-1 over Northwestern China, exceeding the rates over Southwestern China (5.9 ± 0.6 % yr-1) and the three well-known polluted regions in the east (5.3 ± 0.8% yr-1 over Beijing-Tianjin-Hebei, 4.0 ± 0.6% yr-1 over the Yangtze River Delta, and -3.3 ± 0.3% yr-1 over the Pearl River Delta). Subsequent socioeconomic analyses suggest that the rapid NO2 growth over Northwestern China is likely related to the fast developing resource- and pollution-intensive industries along with the “Go West” movement as well as relatively weak emission controls. === Finally, the signal of urbanization between 2005 and 2015 in the prefectural-level cities was identified from the OMI NO2 data, by using a high-resolution NO2 VCD dataset (with a spatial resolution of 0.125° × 0.125°) to derive three relevant metrics (“size relative trend” as a metric for urban area expansion, “mean relative trend” for mean urban pollution, and “max relative trend” for peak intensity). Additionally, the comparisons of the spatial distribution of annual mean NO2 VCDs over China with night light data and population density data in 2010 show the similar spatial patterns of NO2, nighttime light and population density: the correlation coefficients get to 0.74 between NO2 and night light and 0.66 between NO2 and population density. This highlights the consequences of urbanization for pollution and health impacts. Finally, a geographically and temporally weighted regression (GTWR) model is employed to explore the spatio-temporal relationship between NO2 pollution and GDP at a city level over 2005-2013. The GTWR model results show that cities with highest positive estimated parameters were mainly those less developed cities from inland China by providing energy sources and semi-products to coastal cities in the east. For most cities, the NO2 pollution per unit of GDP has declined over 2005-2013, reflecting to some extent the success of local emission control that is accompanied with relocation of production and emissions from the east to the west and from richer to poorer areas. === In summary, our results suggest that the central and local governments should move to achieve and maintain sustainable development both in Eastern China and in the west, perhaps starting by recognizing the importance of removing regional inequality in economic and environmental policies and by optimizing the eco-compensation mechanism and energy structure. More efforts should be made to alleviate NOx and other pollution to achieve sustainable development in Western China, in addition to reducing pollution in the east. === Cui, Yuanzheng. === Thesis Ph.D. Chinese University of Hong Kong 2016. === Includes bibliographical references (leaves ). === Abstracts also in Chinese. === Title from PDF title page (viewed on …). === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only.