| 英文摘要 |
This study has completed PM2.5 mass and chemical species seasonal measurements at the Banqiao, Zhongming, and Xiaogang sites, regular monthly inter-comparison measurements at the Banqiao, Zhongming, and Qianjin sites, and intensive measurements at the Douliu and Chiayi sites. In addition, an extra intensive measurement for regional background at the Taitung site was also completed.
During the collection period, PM2.5 mass concentrations were decreased from north, middle, to the south. Seasonal averages of total stations from spring, summer, autumn, to winter were 37, 18, 50, 53, and 43 μg m-3, respectively. For PM2.5 chemical species concentrations, SO42- was frequently the highest but replaced by organic carbon (OC) or modified NO3- occasionally. Time variations of PM2.5 mass concentrations were consistent between R＆P 2300 speciation sampler and BGI PQ 200 sampler but the values of former were slightly higher during regular monthly inter-comparison. The average of PM2.5 mass concentrations at the Taitung site was 9±1.9 μg m-3 in June 2014. It is of certain that the air quality in Taitung County is the best in Taiwan. The sampling strategy at the Douliu and Chiayi sites was to assess the effects of local pollution after the passage of continental cold high. The Douliu site was more affected by atmospheric stagnancy than other causes. Sources of organic and NO3- aerosols need to be of concern when high PM2.5 mass concentrations occur. In contrast, the Chiayi site was more influenced by motor vehicles and industrial sources than others. This inference was responded by significant NO3- levels when PM2.5 mass concentrations were high at the Chiayi site.
Among the analyzed PM2.5 chemical species, the proportion of NO3- in PM2.5 was magnified significantly by higher PM2.5 mass concentrations. It demonstrates that the contributions of NO3- precursors need to be controlled with high priority. The pollution source factors of the Banqiao, Zhongming, and Xiaogang sites were roughly close to one another from PMF (Positive Matrix Factorization) receptor modelling. Among major pollution source factors, secondary sulfate (Sec S), secondary nitrate (SN), and secondary organic aerosol (SOA) contributed more in cool seasons (spring, autumn, and winter) while biomass burning (BB) contributed more in autumn and winter seasons. According to the modelling results of atmospheric visibility from multiple linear regressions, the significant independent variables were NO2, nss SO42-, and relative humidity at the Banqiao site, NH4+, NO2, and relative humidity at the Zhongming site, and NH4+, temperature, and relative humidity at the Xiaogang site. Relative humidity is noted to be an important factor for all three sites.
To gain PM2.5 chemical speciation monitoring experience and capture recent technical development, this study reviewed 24 scientific papers conducted in Korea, Japan, China, America, Europe, and Taiwan and acquired fruitful results. City, background, national park, and island sites are proposed to set up in the future PM2.5 chemical speciation network in Taiwan. After the discussion in two workshops and consideration of necessary measurement items for easy operation, two speciation samplers are proposed to obtain water-soluble ions and carbonaceous content, respectively, and a third FRM (Federal Reference Method) sampler for obtaining mass concentration by following A205.11C method promulgated by National Analysis Laboratory in Environmental Protection Administration and subsequent elemental analysis. Regular sampling of PM2.5 chemical speciation at every six days is proposed for city, background, and national park sites synchronously or asynchronously while island site is designed as a mobile site for short and intensive collection period.
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