政府自民國73年訂定「台灣地區垃圾處理方案」以來，即積極推動大型都市垃圾焚化廠的興建計畫，以期有效解決國內之垃圾問題。然而根據國內外研究結果顯示，垃圾焚化過程可能排放各種污染物質，包括汞、鉛、鎘、鉻、砷等重金屬及戴奧辛，其中戴奧辛由於對人體的危害甚鉅，最受世人重視。所以國內在推動大型垃圾焚化廠的興建計劃時，常遭民眾質疑將造成戴奧辛污染，因此遭受相當大的阻力。有鑑於此，本研究自民國88年11月起至民國89年7月，分四季針對台北某廢棄物焚化廠附近地區以及桃園縣境內背景濃度點，進行周界大氣中17種毒害最劇之PCDD/PCDF監測，以了解戴奧辛在台北及桃園地區大氣中的流佈，藉此釐清都市垃圾焚化廠所排放之戴奧辛對周圍空氣品質的影響潛勢，並了解大氣中戴奧辛之背景濃度。 根據四季監測結果顯示焚化廠周圍地區之大氣中平均戴奧辛毒性當量濃度以秋、冬季濃度(0.233 pg-TEQ/Nm3)較高，夏季濃度較低(0.106 pg-TEQ/Nm3)。冷季濃度較高之特性與歐美、日等國情況相似。若比較採樣期間各站之大氣中戴奧辛及空氣品質污染物濃度，可發現戴奧辛濃度與PM10及TSP濃度相關性頗佳。在物種分布方面，台北及桃園空品區中大氣的戴奧辛毒性當量濃度及物種分布相似，但焚化廠下風處之B測站周邊大氣中戴奧辛濃度較其他測站為高，上風處之A測站則最低。另外，根據本研究以ISCST3模式模擬台北某廢棄物焚化廠排放戴奧辛污染物擴散結果發現，在污染物濃度擴散值方面則存有相當之差距但在污染物擴散趨勢和實際大氣採樣結果相當吻合。此外，根據大氣參數敏感度測試結果發現戴奧辛污染物在大氣中之擴散受環境中之大氣混合層高度及大氣穩定度影響較大。而風速強弱之影響則是對位於污染源季節風向下風處之地區影響較大。 Taiwan government has implemented “The Wastes Management Plan in Taiwan Area”, prompting the construction and operation of 30 large-scale municipal waste incinerators (MWIs) islandwide to solve the emerging waste treatment problem since 1984. However, the results of relevant studies conducted in some developed countries indicate that the waste incineration process could possibly emit various pollutants including CO, acid gases, particulate matter and dioxins into the atmosphere. Because dioxin is a carcinogen and harmful to human’s immune and reproductive systems, the public places the most emphasis on it. So far Taiwan government suffers some resistance from the people living in the vicinity of proposed MWIs in some areas. To address this important issue, we focus on the understanding of dioxin concentration in the vicinity area of an existing MWI in Taipei and the background dioxin concentration in Taoyuan area by measuring 17 congeners of the most noxious PCDD/PCDF via seasonal samplings in this study. The results obtained from all four seasons’ sampling indicate that the mean dioxin concentration in wintertime (0.233 pg-TEQ/Nm3) is significantly higher than that measured in summertime (0.106 pg-TEQ/Nm3). This trend is similar to the results obtained in other countries. In addition, the seasonal dioxin concentrations are compared with the ambient air quality data such as CO, NOx, SOx, PM10 and TSP sampled from Taipei area to gain better insights. It indicates that the variation of ambient dioxin concentrations is closely correlated with that of PM10 concentrations. With respective to the dioxin distribution, the results indicate that the TEQ concentration of ambient air in sampling site B (directly downwind of the MWI) is of the highest while the sampling site A (upwind of MWI) is of the lowest among all four sampling sites. This implies that existing MWI can be a significant contribution of dioxin in this area. Furthermore, the patterns of the dioxin congener distribution at five sampling sites (including the background site in Taoyuan) are quite similar. In addition the USEPA Industrial Source Complex Short-Term Model (ISCST3) is used to predict the particle-bound dioxin concentration in ambient air in the vicinity of the MWI in Taipei. The results of simulation with ISCST3 reveal that the predicted concentrations are generally lower than the sampling ones, however, similar trends of dioxin dispersion are found in both sampling and model simulation. The sensitivity analysis of the model indicates that the dispersion of dioxin is mainly affected by atmospheric mixing height and stability. On the other hand, in the vicinity of downwind of MWI the dioxin dispersion is more affected by wind speed.
