Long-distance mobile MAX-DOAS observations of NO2 and SO2 over the North China Plain and identification of regional transport and power plant emissions

In this study, the spatiotemporal distribution of the NO2 and SO2 Vertical Columns Densities (VCDs) in the North China Plain (NCP) region was measured by long-distance mobile measurements using a mobile Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument. The mobile observations were performed in both summer (July 2017) and winter (January and February 2018) and the total driving mileage exceeded 3000 km. The concentrations of NO2 and SO2 in different seasons and areas were significantly different. During winter, serious NO2 and SO2 pollution was observed in northern Anhui Province, central Shandong Province, and the Beijing-Tianjin-Hebei Region. The evolution and transportation processes of three typical heavy pollution cases were discussed in detail. Combined with the Weather Research and Forecasting with Chemistry model simulated wind field information, the NO2 transportation flux from northern Jiangsu Province to northern Anhui Province is quantified as 7.12 kg s(-1). Finally, we estimated the NO2 and SO2 emissions from the Dezhou and Hengshui power plants by plume cross section scanning and encircled observations, respectively. The NO2 and SO2 emission fluxes of the Dezhou Power Plant are 0.79 kg s(-1) and 1.11 kg s(-1), respectively, while the NO2 and SO2 emission fluxes of the Hengshui Power Plant are 0.12 kg s(-1) and 0.36 kg s(-1), respectively. This study quantitatively analyzed the transportation of atmospheric pollutants and power plant emissions, which is helpful for understanding the occurrence and evolution of pollution and is also useful for the government to introduce policies to protect and control the atmospheric environment.