| 摘要: | 夲研究探討台南郊區中秋節之前、中秋節慶、中秋節之後、高污染事件及秋季一般空氣品質時期之大氣氣膠化學組成中無機鹽類及羧酸(有機酸)之特性及其生成來源及粒徑分佈。
中秋節之前、中秋節之後、高污染事件大氣氣狀物之全日平均濃度高低依序為NH3>SO2>HNO2>HCl>HNO3>oxalic acid，而SO2濃度在中秋節慶高於NH3。秋季各時期HNO2之夜間濃度大於日間濃度，而HNO3日間濃度高於夜間，顯示日間大氣之HNO2經光化反應轉化生成HNO3。
秋季各時期之malonic acid/succninc acid比值為0.2~1.5，顯示台南郊區採集的大氣氣膠有機酸部份來自尚未轉化之交通排放，另外來自光化反應的貢獻。又oxalic/sulfate之日夜比值，中秋節之前、中秋節慶及中秋節之後的趨勢均為日間大於夜間，顯示此三時期日間氣膠中oxalic acid生成潛勢高於夜間。
台南郊區之NH4+及SO42-主要粒徑均分布於condensation mode之0.19 um及droplet mode之0.54 um，且中秋節慶又以droplet mode之波峰較其他時期顯著，且此時氣膠K+之增量顯然高於其他時期，顯示中秋節除了有節慶烤肉燃燒所產生的污染物排放之外，亦有明顯的光化產物存在，粒徑濃度波峰集中在droplet mode。而Na+及Cl-之粒徑均於coarse mode (6.2 um)有明顯濃度波峰，突顯氣膠中會有來自海洋飛沫的貢獻。
由粒徑2.5 um以下之氣膠Na+與Cl-物種於中秋節之前、中秋節慶、中秋節之後及高污染事件之粒徑濃度相關係數分別為0.49、0.54、0.81及0.95，顯示高污染事件細小海洋飛沫粒徑的形成，具體貢獻在氣膠組成中；而由Ca2+與Mg2+之粒徑濃度相關係數分別高達0.93、0.86、0.93及0.98，提供塵土微粒明確飛散在大氣中的證據。
台南郊區之succinic acid於coarse mode與Na+及Cl-的高度相關趨勢顯示粗粒succinic acid源自海洋飛沫之貢獻，而中秋時期之氣膠glutaric acid粒徑濃度在0.19 um分別較中秋節之前與中秋節之後高出11.3倍及7.3倍，而中秋時期氣膠oxalic acid分別分別較中秋節之前與中秋節之後高出3.4倍及5.1倍，顯示中秋節慶大氣氣膠存在高量的glutaric acid與oxalic acid。而高污染事件glutaric acid主要粒徑分布與NH4+及K+於droplet mode具相同粒徑濃度趨勢，顯示高污染事件受到農廢燃燒排放之影響。
In this research, the temporal chemical compositions, characteristics, formation, sources, and particle distribution of inorganic salts and carboxylic acids (organic acid) of aerosols in Tainan suburban in southern Taiwan were studied during before Mid-Autumn Festival period, Mid-Autumn Festival period, after Mid-Autumn Festival period, autumn clean air quality period, and the PM episode.
The concentration of gaseous pollutants in the atmosphere during before Mid-Autumn Festival period, after Mid-Autumn Festival period and PM episode in the Tainan suburban region is determined to be in the following order NH3> SO2> HNO2> HCl> HNO3> oxalic acid. However, during the Mid-Autumn Festival period, concentration of SO2 is higher than NH3 concentration. Further during all autumn period, the daytime concentration of HNO2 is relatively higher, while during the nighttime concentration of HNO3 is relatively higher, indicating that during the daytime HNO2 is converted to HNO3 by photochemical reactions in atmosphere.
During the all autumn period, the ratio of malonic acid / succinic acid is in the range 0.2 to 1.5, indicating that Tainan suburban aerosol collected were part of the transformation of the traffic emissions via photochemical reaction. During the before Mid-Autumn Festival period, Mid-Autumn Festival period and after Mid-Autumn Festival period the oxalic / sulfate ratio, the daytime is always greater than the nighttime, indicating that during the daytime oxalic acid aerosol formation potential is higher than nighttime.
In Tainan suburban, NH4+ and SO42- were the major particle size distribution in the condensation mode (0.19 µm) and droplet mode (0.54 µm), respectively. The Mid-Autumn Festival celebration droplet mode of the peak is significantly higher than other periods, while concentration of K+ is observed to also increase during this period too, indicating that during the Mid-Autumn festival BBQ, in addition to the pollutants generated by combustion emissions, contributed to the distinct photochemical product in the particle concentration peaks found to be concentrated in the droplet mode. The particle size of Na+ and Cl- are in the coarse mode (6.2 µm), demonstrating the sea spray contribution to atmospheric aerosol.
Moreover, for the particle size below 2.5 um, the correlation coefficient of Na + and Cl- species is 0.49 during the before the Mid-Autumn Festival celebration, 0.54 during the Mid-Autumn Festival, 0.81 during the After Mid-Autumn Festival, while it is 0.95 during the PM episode, an indication of the extent of contribution of sea spray to aerosol pollution particle size. Further, the Ca2 + and Mg2 + high correlation coefficient contribution to aerosol composition concentration in these size were 0.93, 0.86, 0.93 and 0.98, for the before, during, after and PM episode, respectively, providing a clear evidence of dust particles in the atmosphere.
Also, succinic acid shows a high related trend with Na + and Cl- in the coarse mode, indicating that source of succinic acid were also from the contribution of sea spray. During the Mid-Autumn period, aerosol concentration of glutaric acid in the particle size 0.19 m is 11.3 times and 7.3 times higher than periods before Mid-Autumn Festival and After Mid-Autumn Festival, respectively. In addition, oxalic acid during Mid-Autumn Festival period in the aerosol is also higher by 3.4 times and 5.1 times during the periods before Mid-Autumn Festival and after Mid-Autumn Festival, respectively, indicating that during Mid-Autumn Festival celebration, the aerosol shows high amounts of glutaric acid and oxalic acid. The high contamination of glutaric acid for the same particle size distribution and also of NH4 + and K + in the droplet mode size showed the high contamination impact of agricultural waste combustion emissions. |
