Cause Analysis of PM2.5 pollution during the COVID-19 lockdown in Nanning, China

Abstract

To analyze the cause of atmospheric PM2.5 pollution occurred during the COVID-19 lockdown in Nanning of Guangxi, China, Single Particulate Aerosol Mass Spectrometer, Aethalometer, Particulate Lidar, coupled with the monitoring of near-surface gaseous pollutants, meteorological conditions, remote fire spots sensing by satellite and Backward Trajectory Models were conducted during 18–24, Feb 2020. Three haze stages of pre-pollution period (PPP), pollution accumulation period (PAP) and pollution dissipation period (PDP) were identified. The dominant source of PM2.5 in PPP was biomass burning (BB) (40.4%), followed by secondary inorganics (28.1%) and motor vehicle exhaust (11.7%). The PAP was characterized by a large abundance of secondary inorganics, which contributed for 56.1% of the total PM2.5 concentration, followed by BB (17.4%). The absorption Ångström exponent (2.2) in PPP was higher than those of the other two periods. The analysis of fire spots monitored by remote satellite sensing indicated that open BB in regions around Nanning city could be one of the main facotrs matters. The planetary boundary layer-relative humidity-secondary particles matter-particulate matter positive feedback mechanism was employed to elucidate the atompheric process in this study. This study highlights the importance of understanding the role of BB and meteorology in air pollution formation to call for policy for emission control strategies.

Identification of Waterlogging-Prone Areas in Nanning from the Perspective of Urban Expansion

“…Consequently, the ground has become hardened, leading to the loss of the "sponge effect" [3]. The low-lying morphology of urban river basins contribute to the clustering of short-lived productive catchments and the widespread occurrence of river pools in the urban areas, further contributing to waterlogging disasters in Nanning [4,5]. Understanding urbanization and identifying waterlogging-prone areas in cities like Naning can provide valuable insights for addressing waterlogging issues associated with China's urbanization.…”