Variation Characteristics And Influencing Factors Of Surface Ozone In The Pearl River Delta Region In Autumn

With the rapid development of China’s economy and the continuous acceleration of urbanization process,the problem of multi-pollutant pollution in major urban agglomerations,including Beijing-Tianjin-Tangzhou region in China,the sliding Yangtze River Delta region（referred to as the"YRD"）,and the Pearl River Delta region in southern China（referred to as the"PRD"）are serious.Since 2013,ozone has continuously become the leading pollutant in the air of the Pearl River Delta region.Due to the typical nonlinear response relationship between ozone（O₃）and its precursors nitrogen oxides（NO_x）and volatile organic compounds（VOCs）,combined with the combined effects of different types of regional meteorological conditions,the treatment of ozone pollution has become a key topic of current research one.In this paper,three different types of air quality station（urban,suburban and mountainous）are used as research objects,and the daily,weekly changes of O₃ and NO_x in autumn of various regions are analyzed.By constructing meteorological models,the meteorological factors of different regional stations are simulated and evaluated.Then make O₃ prediction equations for representative stations of each region,and identify the main control of ozone concentration in different types of regions by using curve fitting,multiple linear regression analysis and other methods to explore the relationship between each impact factor and O₃.Finally,make a qualitative analysis of the ozone sensitivity of each site,with a view to providing scientific advice for the formulation of ozone prevention and control strategies in the PRD.The results show that O₃ in different types of areas in the PRD has a single peak distribution,and the peak appears around 15:00 in the afternoon.The daily change of ozone in the mountainous areas is the smallest;except for the mountainous areas,the NO_x in all other areas shows a double peak distributed.When the NO_x is in the range of 30～86μg/m³ in the urban area.The ozone exceeding standard rate is 86.84%;when the NO_x concentration range is 21～50μg/m³ in the suburban area,the O₃ exceeding standard rate reaches 91.30%;the mountainous NO_xconcentration range is 13～29μg/m³,the O₃ exceeding standard rate reaches 93.75%.When the O₃ exceeds the standard,the NO_xconcentration range of different regions indicates that the mountainous regions among the three regions is the most sensitive to NO_x.By analyzing the fitting curve of the daytime O₃ and various meteorological factors,it is found that the temperature inflection points of the urban,suburban and mountainous regions affecting the ozone growth rate are 27-30℃,24-28℃and 22.5-25.5℃respectively;the relative humidity inflection points are 55%～75%,60%～80%and 70%～85%.In different wind directions of three types of regions at each sites.The concentration distribution of O₃ and NO_xshows that when the wind direction is NE,the O₃concentration in the urban area is higher;when the wind direction is N and NW,the ozone concentration in the suburban is higher;the higher ozone may occur at mountainous regions.Production activities should be adjusted according to the wind direction in different areas.Finally,combined with the nitrogen oxides,the ozone and various influencing factors by a multiple linear regression analysis found that the main controlling factors affecting O₃concentration are temperature and wind speed in urban regions.The main controlling factors affecting the suburbs O₃ concentration are temperature and relative humidity;the main controlling factors in mountainous areas are temperature and wind speed.According to the linear regression analysis equation between the O₃ and NO_xconcentration between each site and background station Guangzhou MFS during the high pollution period in the PRD,there are certain differences in the response of the generation of O₃ to precursor emissions in different areas.The ozone sensitivity of Guangzhou GMC and Foshan WL sites are the VOCs-limited regime;the Shenzhen HQC and Jiangmen XQ sites are the transition regime.Except for the Guangzhou HNS sites is the VOCs-limited regime in the suburbs,the other three sites are all the transition regime;the mountainous MFS is the typical NO_x-limited regime,while the Zhuhai TJ and Huizhou DYW sites are NO_x control-based transition regime,Zhaoqing KKZ is the transition regime.