本研究計畫共收集了本土性、境外移入(沙塵暴及非沙塵暴)及農廢燃燒等四種不同型態之樣品，以瞭解不同型態PM10事件其氣膠化學組成之差異。每一種事件進行連續約5天之密集採樣，以瞭解各種型態PM10事件其氣膠化學組成於短時間內之變化趨勢。採樣地點選擇中部四個空品測站，採樣期間使用安德森高流量採樣器來收集粗粒徑(PM10~2.5)及細粒徑(PM2.5)懸浮微粒，並分析其陰陽離子及含碳物質之含量。分析結果發現境外移入之兩種事件中，其微粒中之海鹽成份均較非境外移入事件及平常日之海鹽成份為高，此現象在粗粒徑微粒更為明顯。非沙塵暴之境外移入事件，其細粒徑銨離子及硫酸根離子之濃度均極高，分別為平常日之4.7倍及3.1倍，推測係由於挾帶大陸高濃度SO2之氣團，於其長程傳輸過程所衍生出之高量硫酸銨所導致之結果。沙塵暴事件其鈣離子濃度為最高，特別是在粗粒徑微粒。本土性污染事件其細粒徑硝酸根離子濃度及NO3-/PM2.5比值均明顯較其他事件及平常日之濃度為高，顯示在本土性污染事件出現時，其細粒徑硝酸鹽有大量形成之現象。另細粒徑NO3-/SO42-比值亦遠較其他事件及平常日為高，顯示在本土性污染事件出現時，其硝酸鹽之形成速率遠較硫酸鹽之形成速率為快。
Four different types of PM10 episodes, a local episode'a dust-storm episode'a long-range transport with pollutants and a farming waste burning episode, were collected in the present study. In order to further understand the chemical variations during the formation of episode, consecutive sampling period of 5 days were executed. Particulate matter with diameters less than 2.5 .mu.m (PM2.5) and ranging between 10 to 2.5 .mu.m (PM10–2.5) were simultaneously collected at four air-quality monitoring stations in the Taichung area of central Taiwan. Ionic species and carbonaceous materials on aerosol samples collected from four types of episodes were analyzed and compared. The results showed that relatively high levels of sea salts, especially in coarse aerosol, were observed during the episodes of dust-storm and the long-range transport with pollutants. Very high concentrations of NH4 +and SO4 2- in fine aerosols were also observed during the long-range transport with pollutants. These concentrations were about 4.7 and 3.1 times, respectively, higher than normal days. The results could attribute to the formation of ammonium sulfate during the long-range transport with high concentration of SO2 in the air mass. The concentrations of Ca2+ for the episode of dust-storm, especially in coarse aerosol, were much higher than that of other four episodes. The concentrations of NO3 - and the ratios of NO3-/PM2.5 during the local episode were significantly higher than those of other episodes. These results have indicated that much more nitrate in fine aerosol was formed during the local episode. Furthermore, very high ratios of NO3 -/SO4 2- in fine aerosols obtained during the local episode indicating that the formation rate of nitrate was much higher than that of sulfate during the local episode.
