| 摘要: | 汞是一個全球性污染物，主要以氣態元素汞形式經由大氣之長程傳輸到達全球各地。因為甲基汞對神經系統有劇烈毒性作用，所以水域環境中甲基汞的產生機制以及經食物鏈儲存於魚體中的生物累積作用成為環境污染與人體健康危害的重要關切議題。研究顯示水體中與魚體內的汞主要源自於大氣汞沉降，而大氣汞則源自於自然界釋放與人為排放。美國環保署估計全球每年排放至大氣的總汞量為5500 噸，而最主要之人為排放源是燃煤火力發電廠與廢棄物焚化爐，因此大氣汞與酸性污染物前驅物有一項重要共同來源：燃煤火力發電，這也是包含台灣在內的東亞諸國主要的能源供給方式。據估計，中國在2000 年的人為大氣汞排放量佔全球人為總排放量的28%，居世界第一位，因此電腦模式模擬結果顯示在中國的下風處是屬於高大氣汞濃度與沉降量區域，而台灣在秋季至春季間受大陸高氣壓的影響，氣團主要自西方、西北方與北方經中國大陸而來。此外，研究也顯示生質燃燒也可能排放顯著數量的汞到大氣中，而東南亞是已知的主要生質燃燒區域。由於地理位置的關係，以往的研究已證實台灣的環境品質會受到亞洲區域性大氣污染事件（如酸沉降、沙塵暴、生質燃燒等）的影響，而電腦模式模擬結果也顯示台灣是位於高大氣汞濃度與沉降量的地區。因此，本研究計畫之目的即是藉由在高山背景測站的大氣與雨水採樣，分析台灣地區長程輸送大氣汞之來源、源與受體之關係，估算其乾、濕沉降量，探討大氣汞在長程輸送過程之物理與化學行為，並評估其對區域環境之衝擊影響。 ; Mercury (Hg) is a global pollutant, which is distributed worldwide primarily in its gaseous elemental form via long-range atmospheric transport. Due to the neuro-toxicity of mono-methylmercury (MMHg), methylation of Hg in aquatic environments and subsequent bioaccumulation in fish through the food chain is a major human health and environmental concern. Atmospheric deposition has been demonstrated as an important source of Hg to many surface waters and terrestrial environments. Both natural and anthropogenic sources contribute to the Hg in the atmosphere. According to the estimate of USEPA, the annual global input of Hg from all sources to the atmosphere is around 5500 tons. Coal-fired power generation and municipal/medical waste incineration are the major sources of anthropogenic emissions. Therefore, atmospheric Hg and the precursors of acid deposition share an important common source: coal- fired power generation, which is the major type of power supply in East Asia, including Taiwan. China, the largest atmospheric Hg exporting country in the world, is estimated to contribute about 28% of the global anthropogenic Hg emission in 2000. As a result, computer simulation outputs of various international groups all have predicted high atmospheric deposition rates of Hg in regions downwind of China. Between fall and spring, the continental high pressure system dominates so air masses mainly coming from the west, northwest and north passing China before arriving Taiwan. Additionally, recent studies showed that biomass burning could release significant amounts of Hg to the atmosphere. Southeast Asia happens to be a major biomass-burning area, which can influence the air quality in Taiwan. Due to the geographical location, it has been demonstrated that the environmental quality of Taiwan is impacted by regional Asian atmospheric pollution events, such as acid deposition, dust storm, and biomass burning. Moreover, based on model simulation results of various research groups, Taiwan has been predicted to receive high deposition rate of atmospheric Hg, possibly due to regional and/or long-range transport from East and Southeast Asia. Hence, the objectives of this research project are to: (1) figure out the sources of long-range transported atmospheric Hg; (2) evaluate the source-receptor relationships; (3) estimate dry and wet depositional fluxes of atmospheric Hg; (4) discuss the physical and chemical behaviors of atmospheric Hg during long-range transport; (5) assess the potential impacts of long-range transported atmospheric Hg on regional environment. ; 研究期間 9708 ~ 9807 |
