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1 Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan, ROC * Corresponding author address: Dr. Shih-Chun Candice Lung, Research Center for Environmental Changes, Academia Sinica, Taiwan, ROC; E-mail: sclung@rcec.sinica.edu.tw Dust originating from arid and semiarid areas in Central Asia can reach Taiwan during springtime. However, aerosols in a metropolitan region, such as Taipei city, also have significant local sources. In this work, the influence of long-range transport and local pollution, on various water-soluble ions in fine and coarse modes, was investigated for several dust events. Concentration differences between dust-event and non-dust-event days were assessed. Field measurements were conducted in Taipei from February to May 2002. Twelve-hour samples of PM2.5 and PM10 were taken. Ion chromatography was used to analyze water-soluble ions (Na, NH4 +, K, Mg , Ca , Cl , NO3 − , and SO4 2− ). The mean concentrations of Na, NH4 , K, Mg 2+ , Ca , Cl, NO3 , SO4 2− , and PM in the fine mode during the entire sampling campaign were 0.29, 2.87, 0.29, 0.029, 0.13, 0.57, 0.92, 2.68, and 28.2 μg m 3 − , respectively. The corresponding mean concentrations in the coarse mode ( PM2.5-10) were 0.75, 0.30, 0.096, 0.14, 0.63, 0.84, 2.33, 1.60, and 34.0 μg m 3 − , respectively. Results of Principle Component Analysis showed that elevated concentrations of fine Na , K , Mg , Ca , and Cl and coarse Na , Mg , Ca , NO3 − , and SO4 2− on dust-event days were a result of long-range transport. A prolonged influence of long-range transport on concentrations of fine and coarse ions, after dust peaked, was also observed. K, Mg , and Ca increased by about 1.7 to 3.8 fold and Na and Cl increased by 45 210% on dust-event days. Fine modes of NH4 + , NO3 − , and SO4 2− were derived from local pollution, while most coarse NO3 − and some coarse SO4 2− were derived from long-range transport. On average, coarse NO3 − and SO4 2− increased by 67% and 97%, respectively, during dust events. <Back to Index>

Water-soluble Ions of Aerosols in Taipei in Spring 2002