| Summary: | 碩士 === 國立中興大學 === 環境工程學系 === 92 === Abstract
PM2.5 and PM2.5-10 samples were collected on pre-fired quartz filters with a dichotomous sampler in Taichung city during the period from February 2002 to December 2003. The samples were analyzed for elemental carbon (EC) and organic carbon (OC) by using a thermal optical reflectance (TOR) method. The purpose of this study was to investigate the characteristics of EC and OC particulates during several PM10 episodes. The data were also analyzed for further understanding the seasonal variations of the carbonaceous particulates.
Two types of PM10 episodes which included the Asian dust-storm event and the rice-straw waste burning event were observed during the sampling period. Totally there were eight dust events occurred in 2002 and two dust events in 2003. The rice-straw waste burning event, occurred on November 27 in 2002, which was the most serious PM10 episode ever happened in the central Taiwan. The data showed the long-range transported carbonaceous particulates from mainland China to the central Taiwan were not remarkably different form the local ambient aerosols. The average OC/EC in PM10 and PM2.5 during the dust-storm events were 3.6 and 2.7, respectively. These results were similar to those in the non-dust events. However, OC/EC ratio had reached 4.4 in the rice-straw burning event. Large amount of the carbonaceous contents accounted for 43.2％ of PM2.5, which was 1.3 times higher than the annual average data. Since the organic carbon consisted of the primary and the secondary aerosols, a minimum OC/EC method had been applied to estimate the concentrations of the secondary organic carbon (OCsec). The results showed the annual average OCsec accounted for 43.0％ of total organic carbon. The highest percentage of OCsec was found to be 51.5％ in summer, and the lowest (37.9％) was observed in winter.
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