Characteristics, Meteorological Influences, and Transport Source of Ozone Pollution in Zhengzhou City

Abstract

Based on online monitoring data of air quality and meteorological parameters, the long-term variations, spatial differences, and meteorological influencing factors of ground-level ozone (O3) pollution in Zhengzhou were studied. In addition, the transport pathways and potential source regions of O3 were investigated. The results show that surface O3 concentrations at the city station in Zhengzhou City increased significantly during the period 2014-2018 (P<0.05) with a growth rate of 15.50 μg·(m3·a)-1, and the timespan of exceeding pollutant standards was extended. The monthly O3 variations showed an "M" pattern with the seasonal maximum in summer. The diurnal O3 variations showed a "single-peak" pattern with a diurnal concentrations peak at 15:00-16:00, while the diurnal peak at the rural station was relatively high (130.94 μg·m-3). At the urban station, the exceedance probability of O3 concentrations was relative high when hourly temperature (T) exceeded 23℃, relative humidity (RH) was less than 65%, wind speed (WS) ranged 2.0-4.0 m·s-1, and wind direction was southeast or northeast. Based on the multivariate linear fitting of impact factors on O3, the main controlling factors at the city and industrial sites were also identified as T and RH compared to T and WS at the traffic and suburb sites. Back trajectory analysis and potential sources of O3 during different seasons were significantly different, with the dominant transport trajectories during spring and summer being short-distance and slow-moving airflows from the south and northeast; autumn and winter were characterized by long-distance and quick-moving airflows from the northwest. The high O3 concentrations observed in summer were mainly affected by local photochemical formation and regional transport from Hebei, Shandong, and Anhui Provinces.