| dc.description.abstract | 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. | en_US |