| 摘要: | 本研究探討台南郊區之大氣氣膠無機鹽
類及二元有機酸之組成特性變異，結果顯示台
南郊區夏季及秋季氣膠無機鹽類濃度均以
SO4
2-、NO3
-及NH4
+光化產物為最大量，而秋
季高污染時期氣膠NO3
-＞SO4
2-，與在夏季與秋
季非高污染時期為SO4
2-＞NO3
-不同，且氣膠
NO3
- 濃度表現在農廢燃燒時期與高污染時
期，佔PM2.5 質量比例分別為19.6%及18.0%。
在高污染時期氣膠二元有機酸日夜間濃度高
低與夏季相同，依序為oxalic acid＞succinic
acid＞maleic acid，然而高污染時期二元有機酸
之濃度較夏季時期高出約2-3 倍。農廢燃燒時
期，由主成份分析發現NH4
+、NO3
-、SO4
2-、
oxalic acid、K+和Cl-的高相關負荷，顯示二元
有機酸之來源貢獻與光化產物相似，皆為二次
污染；而此時期K+和Cl-之濃度佔PM2.5 質量比
例分別為1.6%及3.3%，與秋季非高污染時期
及秋季高染時期相比，其濃度比例明顯上升，
且oxalic acid 與K+及Cl-的相關係數亦較其他
空氣品質時期更高，顯示農廢燃燒時期除了
K+與Cl-的明顯貢獻外，氣膠中亦存在來自生
物源燃燒產生oxalic acid 的貢獻。在台南郊區
之氣膠無機鹽類與二元有機酸組成之濃度粒
徑分布，由夏季的單峰或雙峰，轉變成秋季的
三峰及更多波峰的形態，高污染時的二元有機
酸最大濃度波峰集中於0.19-0.32 µm 的
condensation mode，顯示高污染時期氣膠有更
明顯的二元有機酸膠凝及光化產物生成貢
獻。此外，氣膠succinic acid (C4)及malonic acid
(C3)之最大濃度波峰與oxalic acid (C2)不同，秋
季非高污染時期及高污染時期之oxalic acid 最
大濃度波峰往更小粒徑位移，顯示秋季氣膠
oxalic acid 是經由C4和C3二元有機酸光化反應
後之最後產物。此外，以空氣品質高斯軌跡傳
遞係數模式(Gaussian trajectory transfercoefficient
model, GTx)探討氣膠污染貢獻來源
發現以面源為最大，污染來源佔35%，其次為
點源的貢獻量佔23%，而上風邊界濃度、高空
沉降以及線源模式則分別佔了17%、14%及
11%，此結果對其台南空品區之管制策略可提
供參考。
In this research, variations of characteristic
compositions of the atmospheric inorganic salts
and low-molecular-weight dicarboxylic acids
(low-Mw DCAs) for Tainan suburban regions
were studied. During summer and autumn, SO4
2-,
NO3
- and NH4
+ are the major inorganic species
with higher NO3
- than SO4
2- during the autumn
episodic period that is different from the higher
SO4
2- than NO3
- during summer and the autumn
non-serious pollution period. The NO3
- sol mass
constitutes 19.6% of PM2.5 mass during the
agricultural waste burning period and 18.0%
during the autumn episodic period. During the
autumn episodic period, variations of the daytime
and nighttime low-Mw DCAs concentrations are
similar to those observed during summer with
oxalic acid being the most abundant followed by
succinic acid and maleic acid. However,
concentrations of low-Mw DCAs during the
autumn episodic period are 2 to 3 time the
concentrations during summer. Results of
principal component analyses reveal that during
the agricultural waste burning period, the high
correlation loadings between NH4
+, NO3
-, SO4
2-,
oxalic acid, K+ and Cl-, indicating that the sources
for low-Mw DCAs are similar to those for
photochemical products; both are considered as
the secondary pollution. During the agricultural
waste burning period, the concentration ratios of
K+ and Cl- to PM2.5 mass are 1.6% and 3.3%,
respectively, which are similar to those during
the autumn non-serious pollution period and the
autumn episodic period; concentrations of K+ and
Cl- obviously increase during the agricultural
2
waste burning period. Oxalic acid during these
periods is more correlated with K+ and Cl- than
during other air quality periods demonstrating
that in addition to K+ and Cl-, a large quantity of
oxalic acid sol is also generated by burning
agricultural wastes. For Tainan suburban region,
the particle size distributions for both aerosol
inorganic salts and low-Mw DCAs change from
single peak or double peaks in summer to triple
or multiple peaks in autumn. During the high
pollution period, the maximum concentration
peaks for low-Mw DCAs dominant in the
condensation mode of 0.19-0.32 µm. This reveals
that particle coagulation and photochemical
products contribute to the observed aerosols
during the high pollution period. Additionally,
the aerosol succinic (C4) and malonic acids (C3)
have different maximum concentration peaks
from oxalic acid (C2). During the autumn
non-serious pollution period and high pollution
period, the maximum concentration peak for
oxalic acid shifts toward the smaller range
indicating that the autumn sol oxalic acid is an
end photochemical product from C4 and C3
low-Mw DCAs. Using the developed aerosol
transformation mechanisms of the Gaussian
trajectory transfer-coefficient model (GTx), the
source apportionment reveals the most dominant
contribution comes form area sources (35%) and
follows by point sources (23%), upwind
boundary sources (17%), top boundary sources
(14%) and line sources (11%). These results
could provide a view to applying proper and
effective strategies for improving air quality in
Tainan air basin. |
