[Characteristics of Surface Ozone and Impact Factors at Different Station Types During the Autumn in Guangzhou].

Surface ozone (O) has become the primary air pollutant in Guangzhou. Due to the influences of topography, meteorological conditions, and differences in precursor emissions, there are also large differences in the characteristics, formation mechanisms, and influencing factors of ozone in different areas of the same city. Based on the ground measurement data for October 2015 at four air quality monitoring stations that represent different types of regions in Guangzhou [urban area:Guangzhou Monitoring Center (GMC); upwind suburbs:Huadu Normal School (HNS); downwind suburbs:Panyu Middle School (PMS); Mountain area:Maofengshan (MFS)] and the WRF simulated meteorological data, the changing characteristics, influencing factors, and sensitivity of O were studied at each station. The results showed that the diurnal variation of O and NO exhibit unimodal and bimodal characteristics (except for NO at the MFS station). The peak ozone concentration appeared on Saturday at the GMC, HNS, and MFS stations, and on Thursday at the PMS station. The ozone concentration at the MFS station was the highest (98.61 μg·m), whereas that at the GMC station was the lowest (44.83 μg·m). The NO inflection point intervals for O at different sites were:GMC:55-90 μg·m; PMS:30-60 μg·m; MFS:10-20 μg·m. The temperature inflection point intervals affecting the rate of O formation at different sites were:GMC:28-30℃; HNS:26-28℃; PMS:24-26℃; however, this was not obvious at the MFS station. The relative humidity inflection point intervals were:GMC:55%-65% ; HNS and PMS:60%-70% ; MFS:80%-85%. The wind speed(WS) of the light wind type was proportional to the O concentration. The O concentration at the PMS site was the highest in the northwest wind direction, and the O concentration at the MFS site was the highest in the other wind directions. By analyzing the multivariate linear fitting of impact factors on the O concentration, the main controlling factors at each site were:GMC:WS and ; PMS and HNS: and RH; MFS:RH and WS. The ozone sensitivity at each site was as follows:GMC and HNS had a VOCs-limited regime, MFS had a NO-limited regime, and PMS had a transition regime.