Abstract: Using the tropospheric monitoring instrument (TROPOMI) O3, NO2 and HCHO products developed by the team of University of Science and Technology of China, combined with the urban boundary data, the spatio-temporal distribution characteristics of ozone and its characteristic precursors (NO2 and HCHO), the seasonal variation and the differences between urban and rural areas of ozone generation control types in the Pearl River Delta region, China, from Sep. 2019 to Feb. 2020 were studied. Firstly, the results show that in terms of spatiotemporal distribution characteristics, the VCD (Vertical column density) of tropospheric NO2 in this area was significantly affected by the fluctuation of industrial sources during the observation period, while the variation of tropospheric HCHO VCD showed obvious seasonal differences. The VCD of tropospheric O3 were relatively high in Oct. 2019 and Feb. 2020, with 44.33 DU and 43.26 DU, respectively, and the ozone pollution in Foshan, Guangzhou and Dongguan was relatively serious. Then, in terms of seasonal variation of O3 generation control type, the ozone formation regime in the central area of the Pearl River Delta (PRD) region had obvious seasonal variation characteristics, it was mainly in the transition regime in autumn, and then turned into a VOCs-limited regime after entering the winter, while the peripheral area of PRD was mainly in the NOx-limited regime. Finally, in terms of urban-rural differences in O3 generating control types, the ozone formation regime in urban areas fluctuated significantly over time. In September 2019, 68.86% of the areas were NOx-limited areas, while in December, the proportion of VOCs-limited areas reached 77.80%. In comparison, the ozone formation regime in rural area was relatively stable, with the proportion of NOx-limited area ranging from 64.58% to 98.31% during the observation period.

Key words: ozone pollution, the Pearl River Delta, tropospheric monitoring instrument, ozone generation process, urban and rural difference