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標題: 台中都會區大氣懸浮微粒粒徑分佈與氯損失之研究
A study of particulate size distributions and chloride depletion in Taichung urban area
作者: 張博彥
Chang, Po Yan
關鍵字: chloride depletion;沙塵暴;relative humidity;[Ca2+]/[Na+];dust storm;粒徑;硝酸鹽;氯損失;[Ca2+]/[Na+];農廢燃燒
出版社: 環境工程學系
沙塵暴過境期間,主要帶來大量粗粒地殼物質,大氣中酸性氣體易與塵土微粒反應,使得硫酸鹽與硝酸鹽的粒徑分佈皆為明顯雙峰分佈,農廢燃燒期間,大氣中氯離子、鉀離子與硝酸鹽細粒明顯增加。關於氯損失,2002年至2004年沙塵暴事件日期間,氣膠平均氯損失為36.1%。相較於非事件日56.6%則減少20.5%,主要受沙塵微粒中豐富鈣成份與HNO3反應所影響。不同粒徑微粒分析得知氯損失隨粒徑減少而增加,因粒徑較小微粒有相對較大表面積。以r0 (=[Na+]/([Cl-]+[NO3-]))為氯損失指標與[Ca2+]/[Na+]及相對濕度RH值進行迴歸,所得經驗公式如r0 = 0.826 - 0.058 × RH - 0.275 × ([Ca2+]/[Na+])。當Ca2+濃度及相對濕度增加,則r0減少,顯示氣膠中Ca(NO3)2比例提高,造成氯損失減少。

The size distributions of ambient particulates were measured monthly in 2004 at Chung-Hsing University in Taichung city. During the sampling period, there were three PM10 episodes representing Asian dust storm event, rice straw waste burning event, and poor dispersion event. This study analyzed the size distributions of the soluble ions including sulfate, nitrate, ammonium, chloride, potassium, and calcium. In addition, the data of the six dust-storm episodes occurred from 2002 to 2004 were analyzed in order to investigate the dust effect on chloride depletion.
During the Asian dust-storm period, a significant amount of crustal aerosols was observed. Since the acidic gases easily reacted with the dust particulates, sulfate and nitrate particulates appear as bi-modal size distribution. During the rice straw waste burning period, the chloride, potassium, and nitrate fine particles significantly increased. Regarding the chloride depletion, the average chloride depletion in aerosol was 36.1% during the Asian dust-storm period. Compared with 56.6% on ordinary days, it reduced 20.5% due to the reaction of HNO3 with the abundant calcium in the dust. Analyzing different size range particles, chloride depletion decreased with increasing particle size because of larger surface area of the smaller particles. Based on the experimental data, a regression equation of r0 (=[Na+]/([Cl-]+[NO3-])) was derived as r0 = 0.826 - 0.058 × RH - 0.275 × ([Ca2+]/[Na+]). r0 decreased with higher Ca2+ and relative humidity. It indicated the higher portion of Ca(NO3)2 causing less chloride depletion.
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