| With rapid economic development and continuing urbanization process, Air quality problems in megacities in Eastern China, such as Beijing-Tianjin-Hebei region, Yangtze River Delta region and Pearl River Delta region are becoming severe increasingly. Atmospheric particulate and ozone, both as important air pollutants, have been known to the public because of extensive impacts on air quality, climate and human health. Research on interaction between particulate matter and ozone will be benefit to reveal the forming mechanism of urban air pollution, providing assistant decision-making strategies for government, and moreover, serving regional society and economy sustainable development. In this study, focusing on YRD region, the mechanism, influencing factors and individual effects on major trace components of interaction between particulate matter and ozone through photochemical process and heterogeneous chemistry were investigated and analyzed with observation data and model simulation.Firstly, air quality monitoring data (PM2.5, PM10, O3, NOx/NOy) and other related data at two stations located in Nanjing during two periods of which March24to30,2008and May5to9,2011were analyzed. During the case of March24to30,2008, when PM10concentration increased120μg/m3, an increment from0.5to0.8appeared in the aerosol optical depth, leading to the volume mixing ratio of ozone reducing6ppb correspondingly. And during the case of May5to9,2011, when PM2.5and PM10concentration increased by a range from4to10μg/m3, AOD rose nearly0.6simultaneously, resulting in a decrease of2ppb in ozone. Results show that the concentration of atmospheric particulate and ozone vary in the opposite direction if meteorological condition and ozone precursor keep stable, in which there are not only the signal of interaction through photochemical process but also that in heterogeneous chemistry process.Secondly, a box model containing ultraviolet radiation transfer process, aerosol optical depth calculator, photochemical process, heterogeneous chemistry process and aerosol thermodynamic equilibrium process was employed to investigate the internal mechanism of interaction between atmospheric particulate and ozone. Sensitivity tests in box model indicate that in photochemical process, the extinction of ultraviolet radiation flux by aerosol impacts on photolysis rate of NO2, which is responsible for the increase of the volume mixing ratio of NO2and reduction of HOx radical, O3and secondary inorganic aerosol, the ratio of△NO2/△PM10,△HOx/△PM10,△O3/△PM10and△SO4+NO3/△PM10are0.12ppb/μg-m3,-0.22ppt/μg-m3,-0.5ppb/μg·m3and-0.05μg·m3/μg·m3, respectively. In heterogeneous chemistry process, the uptake of gaseous components by aerosol impacts on the photochemical formation of ozone, which is responsible for the decrease of NO2, HOx radical and O3, the ratio are-0.01ppb/μg·m3,-0.12ppt/μg-m3,-0.31ppb/μg·m, respectively. However, it may change with different VOCs/NOx, which will further influence the formation of secondary inorganic aerosol. Besides of particulate matter concentration, ratio of soot in particulate matter, temperature, relative humidity and VOCs/NOx are also major influencing factors of interaction between particulate and ozone.Finally, regional air quality model system CMAQ was used to simulate the case of March24to30,2008on interaction between particulate and ozone in YRD region by updating its internal heterogeneous chemistry process module. Simulation suggests that both the interaction through photochemical process and heterogeneous chemistry process effect on the variation of gaseous and aerosol components in concentration, in which the later is dominant. NO2, HOX, O3and secondary SO4+NO3changes in representative urban area in YRD region(Shanghai, Nanjing, Hangzhou, Hefei) due to photochemical impacts are1～3%,-3～-4%,-2～-3%and-1%, respectively, while that due to heterogeneous uptake are-2～-5%,36～51%,5～10%and12～20%, respectively. However, the coupled effects of both interactions appear in a strong non-linear feature. |
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