Estimation the effect of accumulated long-range transported pollutants during a PM2.5 event in Taiwan

Abstract

Fine particulate matter (PM2.5) pollution has attracted much attention in recent years due to its adverse impact on human health and the environment. This study examined a major PM2.5 event observed in Taiwan on March 02–03, 2022, using the Weather Research and Forecasting - Community Multiscale Air Quality (WRF-CMAQ) models. This period also coincided with an outage caused by the power failure of three power plants in Southern Taiwan on March 03, 2022, which created a unique situation to distinguish the impacts of long-range transported (LRT) pollutants and the operation of power plants on the air quality in Taiwan during the high-air-pollution event.Four numerical experiments, Baseline (real case), Replace (Baseline with power plants), No_LRT (Baseline without LRT), and No_0303_LRT (Baseline without LRT on March 03, 2022), were conducted with different initial emission scenarios. The simulation results revealed that the PM2.5 concentrations emitted from three power plants only counted a relatively small proportion in total, while the LRT pollutants were the key factor contributing to the high-concentration PM2.5 during the event. Besides, we figured out that the high PM2.5 concentrations on March 03, 2022 were dominated by the contribution of accumulated LRT. In addition, the results also suggested that the existence of a lee-side vortex, which is considered a potential key issue of the mesoscale system contributes to extreme air pollutant events in Taiwan, causing encouraging conditions for the upward diffusion and northward transport of the PM2.5 concentrations over the southern part of Taiwan, as a result, the distribution of pollution was modulated.