||Kaohsiung, an industrial city with a large amount of air pollution emission,including mercury-containing pollutants, which has great impact on the ambient air quality of Kaohsiung-Pingtung region. In recent years, rapid industrial development in China and the blooming industrial activities consumed a lot of energy, resulting in mercury-containing pollutants emitted to the atmosphere. In addition, Southeast Asia is the one of main regions burning biomass in the world, where open burning activities contribute to regional mercury emissions. In winter and spring, monsoon entrainment with mercury contaminants is long-range transported to the downwind region. Taiwan is located at the downwind of the Asian monsoon region, the dry and wet deposition mechanisms and the intersection of cold and warm fronts caused downwash which make air pollutants deposit down to the lands and waters. Superimposition mechanisms result in the deterioration of ambient air quality in Taiwan.|
Accordingly, to understand the spatiotemporal distribution of atmospheric mercury pollution in southern Taiwan, this study applied “Mercury in Air Detection Method - Cold Vapor Atomic Fluorescence Spectrometry Method” (NIEA A304.10C) adopted from Method IO-5 of United States Environmental Protection Agency to sample and analyze atmospheric mercury in winter and spring seasons, the highest polluted seasons. Field measurement of GEM, GOM, and PHg were conducted at three sampling sites, representing metropolitan, industrial, and background regions, respectively, in southern Taiwan.
In order to determine the transportation routes of air masses, this study applied the NOAA-HYSPLIT Model, Global Fire Map, and integrated meteorological parameters correlation for discussion. In addition, this study reviewed previousliterature of atmospheric mercury concentrations measured in other countries for further comparative analysis.
Field measurement results showed that, during the highly polluted periods, the
concentrations of atmospheric mercury in the Kaohsiung and Pingtung areas of southern Taiwan in winter were higher than those in spring. Particularly, Qianjin and Xiaogang sites had higher atmospheric mercury concentrations in winter than those in spring, while an opposite trend was observed at the Checheng site. During the investigation period, GEM, GOM, and PHg concentrations were in the range of 1.25~11.85 ng/m3, 7.17~497.19 pg/m3, and 0.02~1.16 ng/m3, respectively. The temporal distribution of atmospheric mercury concentration showed that Xiaogang (industrial) > Qianjin (urban) > Checheng (background). The main species of atmospheric mercury was TGM (GEM+GOM) which apportioned as 97.01~87.82% and PHg apportioned as 2.99~12.18% of TAM. These results indicated that atmospheric mercury concentrations were mainly influenced by industrial emissions which are abundant in Kaohsiung, while atmospheric mercury concentrations in Pingtung were influenced by metropolitan emission. Furthermore, the spatial distribution of GOM concentration was ordered as: Xiaogang (1.66%) > Checheng (1.26%) > Qianjin (1.22%). It was observed that the industrial emissions contributed to higher GOM concentration in Kaohsiung, while Pingtung is located at the downwind site of Kaohsiung, where air pollutants could be transported by monsoons or local winds from the upwind areas. Moreover, biomass burning frequently
occurring in spring also contributed high concentration of atmospheric mercury at the
Backward trajectories and global fire map both showed that polluted air
masses containing mercury contaminants were blown from the northern and
northeastern China toward the southern Taiwan by the northeastern Monsoons. Duringthe spring sampling period, the transportation routes of polluted air mass changed slightly, where Xiaogang and Qianjin came mainly from the northern China and influenced by the high pressure system covering the Northeast Asia. The air masses were transported to the East China Sea and then moved a large-scale circulation of wind (anticyclone) southward, while the transportation routes of polluted air mass at Checheng came mainly from the southeastern ocean region. Compared with other cites, the atmosphere mercury concentration measured in southern Taiwan were relatively higher due to densely industrial activities. Further compared with other East Asian countries, the atmospheric mercury concentrations in Kaohsiung and Pingtung were generally lower than China, but higher than Japan, Korea as well as European and American countries, since the development of mercury sampling and abatement technologies in Europe and America were much earlier and thus more advanced than those in Asia. Therefore, the atmospheric mercury concentrations in Asia were mostly higher than those in Europe and North America.