Abstract
The polarization–Raman Lidar combined sun photometer is a powerful method for separating dust and urban haze backscatter, extinction, and mass concentrations. The observation was performed in Beijing during the 2019 National Day parade, the particle depolarization ratio at 532 nm and Lidar ratio at 355 nm are 0.13 ± 0.05 and 52 ± 9 sr, respectively. It is the typical value of a mixture of dust and urban haze. Here we quantify the contributions of cross-regional transported natural dust and urban haze mass concentrations to Beijing’s air quality. There is a significant correlation between urban haze mass concentrations and surface PM2.5 (R = 0.74, p < 0.01). The contributions of local emissions to air pollution during the 2019 National Day parade were insignificant, mainly affected by regional transport, including urban haze in North China plain and Guanzhong Plain (Hebei, Tianjin, Shandong, and Shanxi), and dust aerosol in Mongolia regions and Xinjiang. Moreover, the trans-regional transmission of natural dust dominated the air pollution during the 2019 National Day parade, with a relative contribution to particulate matter mass concentrations exceeding 74% below 4 km. Our results highlight that controlling anthropogenic emissions over regional scales and focusing on the effects of natural dust is crucial and effective to improve Beijing’s air quality.
Highlights
IntroductionMineral (desert) dust and urban haze are the main components of the atmospheric aerosol system over the North China Plain (NCP)
This paper focuses on the contribution of cross-regional transmission of dust and urban haze to Beijing’s air quality during the 2019 National Day military parade
Combining the surface fine particulate matter (PM2 .5 ) and urban haze mass concentrations retrieved by PRL, the urban haze mass concentrations measured by PRL from 13 September to 9 October 2019 were tested and compared
Summary
Mineral (desert) dust and urban haze are the main components of the atmospheric aerosol system over the North China Plain (NCP). NCP is one of the areas with the most anthropogenic aerosol pollution in China [1,2]. Asian dust originates in the interior of Eurasia (Mongolia and the Taklamakan Desert) and travels eastward [3]. Large amounts of mineral dust can be transported from these deserts to the NCP over long distances in the lower free troposphere within a few days. The turbulent exchange process at the interface of the free troposphere and the planetary boundary layer results in the effective mixing of dust with urban haze, presenting vertical stratification of aerosols [4]. It is essential to quantify the impact of these aerosols on air quality in Beijing
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