The seasonal variation and spatial distribution of atmospheric particles at three islands in the Taiwan Strait were investigated. Atmospheric particles (PM 10 ) were collected at three offshore islands (i.e., Kinmen islands, Matsu islands, and Penghu Islands) and two coastal regions (i.e., Xiamen and Fuzhou) in the years of 2008-2012. Field sampling results indicated that the average PM 10 concentrations at the Kinmen islands were generally higher than other sampling sites, suggesting that a superimposition phenomenon was regularly observed during the air pollution episodes at Kinmen Islands and Xiamen region. PM 10 samples were analyzed for their chemical composition, including water-soluble ions, metallic elements, and carbonaceous content. The most abundant water-soluble ionic species of PM 10 were recognized as SO 4 2-, NO 3 -, and NH 4 + , indicating that PM 10 was mainly composed of secondary inorganic aerosols. Although natural crustal elements dominated the metallic content of PM 10 , the most abundant anthropogenic metals of PM 10 were Zn and Pb. Enrichment factor calculations showed that Ni, Cr, and Zn were the enriched elements emitted mainly from anthropogenic sources. Moreover, the OC concentration of PM 10 was always higher than that of EC at all sampling sites. High OC/EC ratios of PM 10 were commonly observed at the sampling sites on the Matsu Islands, the Fuzhou region, and the Penghu Islands. Source apportionment results indicated that vehicular exhausts were the main source of PM 10 , and followed by industrial boilers, secondary aerosols, soil dusts, biomass burning, petrochemical plants, steel plants, oceanic spray, and cement plants at the island and coastal sampling sites in the Taiwan Strait.
This study aimed to use a newly developed weather and air quality model, WRF-Chem, to simulate and analyze formation of high-concentrated ozone (O3) in the ambient air of southwestern Taiwan before the invasion of tropical typhoons. Two typical typhoons, Nanmadol and Usagi that occurred in 2011 and 2013, respectively, were simulated in this study. The O3concentration variation patterns in the ambient air of both offshore and inland parts of southwestern Taiwan were collected and analyzed. The results indicated that the high O3concentration observed in southwestern Taiwan before typhoon arrived was mainly caused by the western Pacific subtropical high (WPSH) shrouding it. On the other hand, the latter increase in ambient O3concentration about 1 to 2 days before issuing sea warning was mainly due to both contributions of weakening WPSH and intensifying leeward side effects. For both cases, atmospheric subsidence occurred to result in low ambient air quality. The invasion of typhoons made ambient O3concentration enhanced up to 2-3-fold compared to its normal concentration in summer. Based on the simulated O3concentration variation results in this study, it is demonstrated that the space-fading patterns of O3before typhoon arrives also can be used as references for predicting typhoon moving tracks 1.0 to 2.0 days before landfall of typhoons.
Due to the distinct geographical and meteorological conditions of Taiwan, air pollutants concentrations in the ambient air of it may vary with seasons. Accordingly, this study aimed to investigate the formation of high O3concentration in the ambient air of Southern Taiwan during summers. A high O3concentration case occurring between June 28 and July 2, 2013, was modeled and analyzed with WRF-Chem meteorological and air quality model. During the investigated period, a typical western Pacific subtropical high (WPSH) covered most East Asia, including Taiwan and its surrounding areas. The observations showed strong correlations between WPSH invasion and forming high O3concentrations. The dispersion of air pollutants in the ambient air is not sufficient to dilute their concentrations. In the afternoon of June 30, more than 60% of the air quality monitoring stations found O3concentrations exceeding 100 ppb, which were 2~3 times higher than their normal concentrations. Model simulation results verified that the presence of the WPSH hindered the dilution and transportation of air pollutants in ambient air. In addition, the air quality would be getting worse due to the leeward sides caused by the counter clockwise vertex formed in Southwestern Taiwan.
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