| dc.description.abstract | China dust storms play a significant role in the radiation budget, climate change, visibility degradation, health effects, and the equilibrium of ecosystems in East Asia (Chung et al., 1996). In collaboration with the major countries of Pacific Rim on the monitoring of China outflow, this study collects PM2.5 and PM10 at Shi-Men in Taipei County from March to May in 2001. Aerosol mass concentration, water-soluble ions, carbonaceous content, and elemental content were resolved from the collected filters.
The results demonstrate a contrast of aerosol chemical properties between dust storm events and normal days in the Taiwan northern coast. During dust storm events, the average mass from PM2.5, PM10, and PM10-2.5 was 43.7, 124.4, and 80.8 μg/m3, respectively. In contrast, that of PM2.5, PM10, and PM10-2.5 was 26.0, 50.6, and 24.5 μg/m3, respectively. It shows that PM10-2.5 dominated PM10 fraction with more than triple fold in the dust events as compared to normal days. In addition, the concentrated species in the dust storm events were Ca2+, Ca, Fe, and Si. For the ratio of organic carbon to elemental carbon (OC/EC), the values in the dust storm events ranged between 1.5~2.29 that were smaller than 3.26~3.30 in the normal days. More, the fraction of SO42- in PM10 and PM2.5 during the events was found smaller than that of normal days. This result implies the hindrance of dust storms on the formation of secondary aerosols.
In validating the analytical accuracy on aerosol composition, a method of reconstructed mass was adopted to convert aerosol species into aerosol compounds. The method increased the resolved mass fraction PM2.5 and PM10 to a value of 79.3 and 94%, respectively. From the calculation of chlorine loss, we found 61.8% of PM2.5 is secondary sulfate, whereas 38.5 and 27.6% of PM10 is secondary sulfate and sea-salt aerosol, respectively. Meanwhile, the absolute principal component analysis shows the most significant source of PM2.5 contributed 65.5% of mass concentration, which is a source mixed with anthropogenic activity, vehicle emission, and secondary reactions. In contrast, sea-salt spraying, resuspended dusts, agricultural burning, and part of the secondary reactions contributed 61.7% of PM10. The consistency between chlorine loss and absolute principal component methods confirms the results of aerosol source apportionment in this study. | en_US |