Investigations of spatial-temporal distribution and regional transport in typical section of NO2 in eastern China using Mobile-DOAS

Abstract

As the most economically, industrially, and transport-developed region in China, Eastern China suffers from severe pollution due to anthropogenic emissions. To better understand the distribution and transport of pollutants in this region, a regional-scale long-distance mobile observation experiment was conducted from August to September 2020 in the North China Plain (NCP), the Yangtze River Delta (YRD), and the southeastern coastal (SEC) areas, obtaining the distribution characteristics of NO₂ column concentrations in different areas. The NO₂ pollution in the Beijing-Tianjin-Hebei region of the NCP, especially along the southwest measurement line on the eastern side of the Taihang Mountains, is the most severe. The NO₂ values in the SEC only show an increase around several large cities. The highest NO₂ values were recorded on the Hefei to Shanghai segment in the YRD. The study further discusses the NO₂ transport process along the typical transport section from Hefei to Shanghai. By combining WRF-Chem model simulations, the NO₂ transport flux across the section was quantitatively analyzed. The results showed that under a southerly wind field, the measured and modeled NO₂ transport fluxes were 10.588 kg/s and 13.254 kg/s, respectively; under a northerly wind field, the measured and modeled fluxes were 28.881 kg/s and 32.207 kg/s, respectively. The measured values differed by 2.73 times, and the modeled values differed by 2.43 times, indicating a significant difference in transport flux between the north and south directions. Combining emission inventory data, it was found that the NO_x emission rate in the northern part of the YRD is 2.03 times that of the southern part, indicating high NO_x emissions. This study reveals the differences in pollution transport flux in the north-south direction of the region, providing data support for exploring new pathways for regional linkage, coordinated management, and win-win cooperation in total pollutant control.