| dc.description.abstract | This study associated with PM2.5 (particulate matter with an aerodynamic diameter less than or equal to 2.5 μm) chemical speciation at the Banqiao, Zhongming, and Xiaogang sites in “The 2020 Project of Chemical Speciation Monitoring and Analysis of Fine Particulate Matter (PM2.5)” and optical measurements in “Plan and Application of Atmospherical Visibility Monitoring Construction” to investigate PM2.5 chemical speciation and environmental factors on atmospheric visibility in Taiwan’s metropolis. This work used PM2.5 optical properties to resolve aerosol types and potential sources and revealed the optical effects of aerosol chemical components in different seasons during the study.
The atmospheric visibilities from estimated and manual observations were roughly consistent in time variation, but estimated values were much higher than manual ones from comparisons among manual observation, conversion from the atmospheric optical property, and estimates from PM2.5 chemical speciation. The differences mentioned above are related to the visibility conversion method, aerosol compound forms, and objects selected from manual observation. Organic matter, ammonium sulfate, and ammonium nitrate of PM2.5 chemical components affect atmospheric visibility predominantly. Low temperature and high relative humidity degraded atmospheric visibility significantly but turned insignificant for high PM2.5 levels. The diurnal and nocturnal variations of aerosol light absorption and scattering coefficients were associated with traffic emissions and meteorological factors. The hourly variations of black carbon (BC) in a day were also related to traffic emissions. Likewise, traffic emissions were a dominant source of BC (around 80%) estimated from the Aethalometer Model.
This study adopted conditional bivariate probability function to explore high polluting potential sources at the Banqiao, Zhongming (Xitun), and Xiaogang sites. The results showed that industrial parks and municipal incinerators might pollute the Banqiao site in addition to traffic emissions. The Zhongming (Xitun) site was influenced by the west wind transporting high polluting source contributions from the west plus additional biomass burning from the south. In comparison, the Xiaogang site was under the influence of ship emissions, industrial parks, iron and steel manufacturing, refinery, and traffic pollutions. Based on aerosol optical depth (AOD) and AE (Ångström exponent), the three sites were classified into urban-type aerosols mostly discharged by vehicle emissions in four seasons. For PM2.5 >25 μg m-3, high AOD values mainly occurred in high wind speed and low relative humidity environments at the Zhongming and Xiaogang sites.
In summary, atmospheric visibility will be affected by different assessment bases. Organic carbon, ammonium sulfate, and ammonium nitrate affected atmospheric visibility greater than other components in PM2.5 chemical speciation. Mobile sources and environmental factors influence atmospheric visibility mainly in Taiwan’s metropolis. In principle, the aerosol types at the three sites are fine urban-type aerosols, which demonstrates a significant influence of PM2.5. | en_US |