| dc.description.abstract | Recently, the industrial outflow and yellow-dust transported from China gained a lot of attentions. These pollutions may be transported to Taiwan by cold continental high-pressure system and northeast monsoon. In this study, filter-based aerosol was collected at Shi-Men site, the northern tip of Taiwan, from June 2005 to April 2006. The concentrations of air pollutants are lower in summer, while that in the other three seasons are higher.
The SO2 at Shi-Men site is found transported mostly from Taipei Basin. Although the concentration of SO2 tends to increase during yellow-dust and cold high-pressure affecting periods, the occurrence time shares only 5% of the sampling time. In contrast, the time when SO2 transported from Taipei Basin is around 70% of the aerosol observation time in this study. Similarly, NH3 is also produced locally most of the time, however, a great amount of NH3 is observed if the front of dust flow passes through the industrialized China’s coastline. Meanwhile, the distributions of HNO3 and HNO2 make no difference among different air masses. For the abundance compared between aerosol and precursor gases, aerosol concentration is found higher than its precursor gases.
The secondary aerosol is higher for China’s coastline transport, while primary aerosol is more contributed from local sources, oceanic transport, and anticyclonic outflow for the four types of back trajectory during non-dust period. A high correlation is found between nss-Ca2+ and secondary aerosol when under the influence of yellow-dust. Moreover, a consistent relationship is observed between nss-SO42- and SO2 for air masses transported from China’s coastline.
Aerosol carbon is mainly contributed from Taiwan as it shows high concentration in summer and low value in winter when under the influence of continental cold high and northeast monsoon. The variations of estimated secondary organic carbon are consistent with low-temperature volatilized carbon fraction OC2, it suggests that the sources of OC2 are related to secondary organic carbon.
The measured aerosol pH values are acidic which might be affected by the abundance of nss-SO42-. The lowest aerosol acidity is observed when the air masses are transported from the ocean, while aerosol acidity is the highest for China’s coastline transport among the four back trajectory types. The calculation of NH4+ / nss-SO42- molar ratios shows that the atmosphere is in the state of ammonium-rich when the air masses are from local area, the ocean, anticyclonic outflow, and yellow-dust transport. In contrast, the state of ammonium poor is found when the air masses pass through China’s coastline.
For most of the time, the amount of succinic acid is obvious the lowest among the analyzed dicarboxylic acids. It indicates that dicarboxylic acids are converted from secondary photochemical reactions as C3/C4 ratios are mostly above 1. However, the C3/C4 ratios are turned to vary from 0.4 to 0.6 when under the influence of anticyclonic outflow after the passage of yellow-dust. This then suggests that the formation of dicarboxylic acids is shifted to originate from primary emissions. | en_US |