| dc.description.abstract | The contributions of industrial aerosols from vast coastal areas in the East China and the outbreaks of dust storms frequently occurred in northwestern desert areas in springtime make China a major source region of aerosols in the East Asia. Taiwan is situated in the lee side of air masses transported from China through cold high-pressure system (cold-high). The aerosols transported from industrial emissions and yellow dusts through a right weather system will affect the air quality in Taiwan.
This study chose Shi-Men in Taipei County as the site for aerosol observation. Shi-Men is the first place in the whole island to encounter air masses from China due to its location in northern tip of Taiwan. This study collected atmospheric aerosols in the fixed time interval of each month from May 2003 to April 2004. In total, 201 samples of PM10 and PM2.5 were collected to resolve mass concentration, elemental contents, water-soluble ions, and carbonaceous contents.
To investigate the effects of transported air masses, this study divided the study periods into periods under the influence of cold-high and non-cold-high. The air masses were further classified into 7 types of air masses using HYSPLIT back trajectory model from NOAA. This classification of air masses was adopted to differentiate variations and the enhancements of aerosol compositions of the individual air mass. The effects of yellow dusts on aerosol properties in this year will also be discussed.
The results show that the average PM10 for the periods of non-cold-high and cold-high were 30 μgm-3 and 60 μgm-3, respectively. Water-soluble Na+ and Cl- of PM10 under the influence of cold-high were 4-10 folds more than that of non-cold-high. PM10 NH4+ and SO42- in cold-high periods were increased 70 and 74 %, respectively. Similarly, PM2.5 NH4+ and SO42- under the influence of cold-high increased 66 and 70 %, respectively. Meanwhile, NO3- both in PM10 and PM2.5 enhanced 2 times for the periods of cold-high. In contrast, aerosol organic carbon only increased 12 % under the influence of cold-high and even without a significant effect for aerosol elemental carbon. The Al, Fe, and Ca were enhanced 60-80 % under the influence of cold-high.
Among the seven types of aerosol masses, aerosol mass concentrations were the lowest for local source contributions. Sulfate ion was predominant and with only a small contribution from sea-salts in local source type. The sea-salt aerosols increased 33 % for oceanic transport in yellow-dust periods as compared with that of non-yellow-dust periods. In addition, the sea-salt aerosols were 2.8-8 times higher for oceanic transport in non-yellow-dust periods and 4-11 folds higher in yellow-dust periods than that in local source contributions. Notably, the enhancement of aerosol mass was 1.5-2 folds for the air masses from coastal areas during yellow-dust periods to that of local source contributions. Moreover, sulfate ion was 2 times higher, elemental Al, Fe, and Ca were more than 3 times, and potassium ions was 6 times higher for the comparison between the air masses from coastal areas during yellow-dust periods and that of local source contributions. For the aerosols in non-yellow-dust high-pressure recapitulation periods, sulfate ion, nitrate ion, and carbonaceous materials were major components with concentrations 15-135 % higher than that from local source contributions. Nitrate ion was 2-3 times higher and aerosol carbon was 25-40 % higher in yellow-dust high-pressure recapitulation periods than that from local source contributions.
The coarse particles (PM2.5-10) in yellow-dust events were 0.9-1.5 times higher than that in non-yellow-dust periods in 2004. The third yellow-dust event was noted the most severe one in 2004. The water-soluble ions of PM2.5 aerosols in yellow-dust events were only slightly enhanced. However, Cl-, Na+, Mg2+ and Ca2+ in PM2.5-10 were significantly increased 0.9-7.5 times during yellow-dust events. It is noted that NH4+ was the species decreased both in PM2.5 and PM10 aerosols in yellow-dust events. Aerosol organic carbon tended to increase but the increase of elemental carbon was insignificant in yellow-dust events. For the crustal materials in PM2.5-10 like Al, Ca, and Fe, they were 9-15 times greater in yellow-dust events. | en_US |