| dc.description.abstract | Taiwan is located downwind of the East Asian continent and thus could be under the influence of anthropogenic air pollutant emission, including mercury (Hg) and the other heavy metals, from East Asia. In 2009, weekly wet deposition samples have been collected at Anbu, Jhongli and Chiayi sites in Taiwan for Hg and heavy metal (As, Cd, Pb, V, and Zn) analyses. These data were used to discuss seasonal trends for Hg and heavy metals in wet deposition and to evaluate the contribution of regional/long-range transport.
The volume weight mean (VWM) concentrations of Hg at Anbu, Jhongli, Chiayi were 9.5, 10.7 and 13.5 ng/L, respectively. The concentration of Hg at Chiayi is higher than at the northern sites, Anbu and Jhongli. At Anbu site, the concentrations of Hg in wet deposition were higher in summer than in other seasons, indicating the importance of Hg0 oxidation and/or scavenging of upper-altitude Hg(II) by deep convection.
For the other heavy metals, the VWM concentration of As, Cd, Pb, V and Zn at Anbu site were 0.6, 0.1, 3.8, 0.7 and 31.0 ?g/L, respectively. At Jhongli site, the VWM concentration of As, Cd, Pb, V and Zn were 0.3, 0.1, 2.2, 0.8 and 24.2 ?g/L, respectively. The VWM concentration of As, Cd, Pb, V and Zn at Chiayi site were 0.1, 0.1, 1.0, 0.5 and 14.2 ?g/L, respectively. Higher concentrations of these heavy metals were usually observed at Anbu while lower concentrations were observed at Chiayi. Regarding the seasonal distribution of concentrations of theses heavy metals, lower values were usually observed in summer. Seasonal variations in heavy metal concentrations were correlated with air masses origin. In summer, air masses came mainly from the Pacific Ocean and South China Sea, which were relatively clean marine air. Between fall and spring, air masses passed the East Asian continent prior to reaching Taiwan, contributing to the elevated heavy metal concentrations. The air masses in winter monsoon brought large amount of pollutants and caused higher concentrations in wet depositions, indicating the importance of regional/long-range transport to Taiwan.
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