Abstract
This study investigated the mass concentration and size distribution of atmospheric aerosols collected at the Pescadores Islands during Asian dust storm periods in the years of 2001 and 2002. As part of an island-wide Asian dust sampling network covering Taiwan and its surrounding islands, an atmospheric aerosol sampling site was established at Xiaumen, Pescadores Islands since March 2001. Xiaumen was at the northwest tip of the Pescadores Islands located at the center of Taiwan Strait and approximately 110 kilometers from the West Coast of the Taiwan Main Island. The sampling protocol was conducted to collect sea level atmospheric aerosols for further physical and chemical analysis. This study revealed that five Asian dust storms invaded the Pescadores Islands during the sampling campaign. The mass concentration of atmospheric aerosols, particularly PM(subscript 2.5-1O), were 2-3 times higher than background levels (i.e., non-Asian dust storm periods). Comparison of hourly PM10 concentration between Xiaumen and ambient air quality monitoring stations in Taiwan indicated that Asian dust storms usually invaded from either the northeast or the northwest and could last for approximately 2 - 4 days. Moreover, Asian dusts could be preliminarily validated in situ by observing the change of their apparent colors from dark gray to light brown. Comparison of hourly PM10 concentration measured at the Pescadores Islands and Taiwan Main Island during the Asian dust storm periods showed that the Asian dust storm invaded Taiwan from either the northwest or the northeast. Increasing both concentration and coarse particle mode in the size distribution of atmospheric aerosols validated the invasion of Asian dust storms. Significant increase of SO4(superscript 2-), Cl(superscript -), Na(superscript +), NH4(superscript +), Mg(superscript 2+) and Ca^(superscript 2+) concentration on coarse particle mode was also observed for Asian dusts. This suggested that not just natural soil dusts but also anthropogenic pollutants and oceanic spray could accompany the Asian dust storms and arrive at the Pescadores Islands.
Highlights
Asian dust storms were originally blown from inland arid and semi-arid areas located in Northwest China and Mongolia in Asian continent (Uno et al 2002)
The variation of daily PM10 concentration at the Pescadores Islands was well consistent with ambient air quality data from monitoring stations located in Taiwan (Fig. 3)
In comparison with the hourly PM10 concentration measured in Beijing, China (Zhang and Wang 2001), Asian dust storms reached the Pescadores Islands approximately 36 - 72 hours later than Beijing, which concurred with model simulations
Summary
Asian dust storms were originally blown from inland arid and semi-arid areas located in Northwest China and Mongolia in Asian continent (Uno et al 2002). Asian dusts could be transported easterly from their sources to west pacific countries such as Korea, Japan, and Taiwan (Kagawa et al 2001; Peng et al 2002; Chou et al 2004; Lin et al 2004). This could have significant environmental effects, including ambient air quality deterioration, atmospheric visibility impairment, radiation energy reduction, mineral deposition, and acid rain neutralization (Zhang and An 1999; Terada et al 2002; Chen et al 2004). Results obtained from the investigation on source apportioning atmospheric aerosols at an Asian dust episode in metro Kaohsiung indicated that the percentage of fugitive dusts increased significantly from 8.5% (regular periods) to 26.2% (Asian dust storm periods) (Liu and Yuan 2000)
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