|dc.description.abstract||The characteristics and source contributions are very important in residents’ health effect and source control. This work compiles 63 samples of PM2.5 mass and speciations manually collected at three air quality monitoring stations (Xinzhuang, Chungming, and Siaogang) located in the metropolitan areas of northern, central, and southern Taiwan from March 9, 2011 to March 29, 2012. The aim of this work is studying seasonal variations of urban PM2.5, the effects of various measurement methods and instrumental units, different weather types, and potential source contributions on PM2.5. Moreover, the relationship of various PM2.5 speciations and sources with visibility is also investigated.
The results show that the highest PM2.5 mass concentrations at the Xinzhuang and Chungming stations are occurred in spring, while that of the Siaogang station is in winter. For the weather patterns results, the sources of Xinzhuang and Chungming stations are contributed from local sources as well as long-range transport of Asian continent based on weather pattern analysis. In contrast, Siaogang station is affected locally plus poor ventilation in the environment. The major species is SO42- in almost all the stations and seasons except for the summer. Organic carbon concentration is very close to SO42- and highest vaporization proportion of NO3- is observed in summer while other volatile ions are without seasonal variations.
For the whole observation study, the collected PM2.5 concentration is the lowest when using R&P 2000 FRM (Federal Reference Method), highest for referring to the data of air quality stations, and in the middle for the data from R&P2300 speciation sampler. In addition, the differences among sampling methods become wider when the collected concentrations are higher. The deviations between R&P2000 and R&P2300 are inferred to be affected by honeycomb denuders installed in the R&P 2300 sampler.
High PM2.5 concentration was observed in the north for the weather patterns of High Pressure Peripheral Circulation (HPPC), High Pressure system Pushing (HPP), and Warm area Ahead of a cold Front coupling with Weak Southern Wind (WAF+WSW) based on the weather pattern analysis (Chuang et al., 2008). Lower PM2.5 concentration frequently occurred in the periods of Northeastern and Southwest monsoons. In contrast, high PM2.5 concentrations were normally appeared in HPPC, HPP, and Northeastern monsoon and low for WAF+WSW and Southwestern monsoon in the central and southern Taiwan.
Six source types were resolved from PMF (U.S. EPA, 2008) (Positive Matrix Factorization) source apportionment for all three stations. Secondary nitrate and chloride contributed highest followed by Secondary sulfate, Gasoline emission, Soil dust, Diesel emission, and Biomass burning. Multiple regression analysis on atmospheric visibility using PM2.5 species, sources types, and environmental factors showed that visibility is mainly reduced by the water content deliquesced from secondary inorganic ions.
In summary, Taiwan urban PM2.5 is varied by seasons and weather patterns. Traffic emissions contributed significantly to atmospheric PM2.5, which may help the authorities in urban pollution control and assessment. Moreover, secondary inorganic ions are significant in reducing urban visibility.||en_US|