| dc.description.abstract | This article observes PM2.5 (suspended particles with aerodynamic diameters less than or equal to 2.5 μm) and water-soluble inorganic ions (WSIIs) in Taichung City from January to February 2021 and in the Lulin Mountain area in March and April, then analyze the sources and formation of pollution in urban and mountainous areas.
In the Taichung metropolitan area, the primary WSIIs (NO3-, SO42-, and NH4+) exhibited dynamic changes similar to PM2.5. When wind speeds were below 1.6 m s-1, pollutant concentrations tended to increase, while wind speeds above 1.6 m s-1 suggested that SO42- originated mainly from outside the region, NO3- was influenced by traffic emissions, Na+ and Mg2+ were affected by sea salt, and Cl- could come from both sea salt and other pollution sources. The mass concentration of NO2- showed significant diurnal variation, with NO2 being its primary precursor pollutant.
At the Lulin Mountain station, when affected by biomass burning (BB) smoke plumes, there is a significant increase in average PM2.5 and primary WSIIs mass concentrations. During valley wind occurrences, the mass concentrations of WSIIs also rise, indicating that valley winds contribute to anthropogenic pollution. During the BB event days, cloud and fog events were observed, leading to a decrease in pollutant concentrations due to wet removal effects. In the afternoons of the two days of BB events, the number concentration of aerosol particles measuring 40 nm increased, along with a rising volume concentration of particles greater than 100 nm. This demonstrates the hygroscopic growth characteristics of aerosols, while the primary WSIIs exhibited similar trends in concentration changes, indicating the contribution of fine particulate aerosols to WSIIs in the Lulin Mountain area.
This article discusses the combination patterns of the primary WSIIs in the atmosphere based on the molar concentration ratio of [NH4+]/[SO42-]. It finds that ammonia is abundant in Taichung City, and the main WSIIs present as (NH4)2SO4, NH4NO3, and other compounds, with the generation of N2O5. In the Lulin Mountain station, ammonia is less abundant, and the main WSIIs may include (NH4)2SO4, along with NH4HSO4, H(NH4)3(SO4)2 (Letovicite), and NH4NO3. | en_US |