| Summary: | 碩士 === 國立成功大學 === 環境工程學系碩博士班 === 97 === This study had been conducted to investigate the composition of airborne particulate matter and the precursor gases at Dalia station in the Southern Taiwan Air Basin.The back-trajectory model had also been applied to evaluate the potential sources that caused air pollution episode event in this area. The airborne particulate matter and precursor gases were sampled by Microorifice Uniform Deposit Impactor (MOUDI), Nano-MOUDI, and Annular Denuder System (ADS). The compositions of water-soluble ion species and precursor gases were detected by ion chromatography (IC).There were total 44 samples which were categoried into four groups: non-episode daytime, non-episode nighttime, episode daytime, and episode nighttime in this study.
The results showed that the airborne particle size distribution in the station was a typical tri-modal distribution and the concentrations of course particles and fine particles were increasing in episode event. The percentages of PM2.5 in PM10 were 75.4 %and 79.2% during episode days and episode nights, respectively. This result implied that the PM concentration in this station may influenced by anthropogenic sources. The PM concentration increased as increasing relative humidity in episode day and rising temperature in non-episode day. The mass concentrations of PM0.1-2.5 were influenced by ambient temperature and relative humidity.
The concentrations of water-soluble ions in airborne particulate matter were increasing in episode day. The dominant particular components were secondary ions (NH4+, SO42-, and NO3-), which appeared in accumulation mode of PM2.5. In episode daytime the secondary ions accounted for 46.3% of PM mass, This value is higher than that in non-episode daytime (32.1%). In episode nighttime the secondary ions accounted for 56.9% of PM mass, the value is also higher than that in non-episode nighttime (32.1%).
The observation data also indicated that the concentration of precursor gases (HCl, HNO3, and SO2) during episodes were higher than those in non-episodes. The gas-to-particle conversion ratio of NO2 and SO2 were high during episode days.
The results of back-trajectory model analysis showed that the air mass transported north boundary in winter time. The plume approached Da-Liao station is north by west boundary in the daytime and caused high occurrence of episode day. The secondary ion was mainly sulfate which implied that high SO2 concentration emitted from nearby industrial area. In nighttime, air mass approached Da-Liao station from northeast and northern, high occurrence of episode day was observed in northern, and followed by northeast. In summer, the results of back-trajectory model analysis showed that the air mass came from ocean, which may attribute to the less pulluted plume.Above all the PM concentration at Da-Liao station was influenced strongly by air mass travelling through industrial area with dense emissions.
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