Characteristics and impacts of fine particulates from the largest power plant plume in Taiwan

In this study, the impact of the coal-fired Taichung Power Plant (TPP) plume in Taiwan during an observation experiment from Oct. 31 to Nov. 22, 2021, is simulated. We used the WRF/CMAQ and HYSPLIT models to analyze the changes in the PM_2.5 concentration and the contribution percentage of major PM_2.5 species along the forward trajectory of the TPP plume. Twenty trajectories with high PM_2.5 concentrations above the chimney are divided into three types: transport to inland (TI), northeast monsoon transport southward (NMTS), and transport to sea (TS). The first kind, which exhibits mostly windy cases, is more harmful to people. Moreover, the largest proportion of the plume when it first exits the stack is SO₄ ²⁻ (sulfate), which slightly decreases over time. The proportions of OM (organic matter) and NO₃ ⁻ (nitrate) slightly increased, and the proportion of NH₄ ⁺ (ammonium ions) increased but not significantly. With the generation of low volatility/semi-volatile SOA (secondary organic aerosol), the proportion of OM significantly increases along the trajectory. Daytime photochemical reactions increase the radical concentrations, leading to an increase in the generation of low volatility/semi-volatile SOA and thus an increase in the proportion of OM. However, the proportion of NO₃ ⁻ in the smoke plume is smaller than that in other major PM_2.5 species. Near the chimney, ANO₃ (nitrate) accounts for a larger proportion of NO₃ ⁻ than HNO₃ (nitrate acid). Furthermore, a sensitivity test shows that the height of the TPP that is reduced from 250 m to 150 m can have less effect on the environment.