| Summary: | 碩士 === 國立清華大學 === 化學系 === 96 === Dioxin generated from combustion widely distributed in the air and directly breathed by human. Simultaneously, the same dioxin might also adhere to dust in the air and deposited on our living environment and indirectly intake by human. Both dioxin exposure routes inevitably threat human health. Domestically, there are numerous researches about dioxin in air. On contrast, little is done about dioxin in dust. This study sampled air and dust from coast area and inland area in Taoyuan County and analyzed their dioxin composition and pattern. Multi-variable statistical analysis method was employed to study the difference in dioxin composition and pattern between dusts collected from different area and of different size as well as between dust and air.
The analytical results indicate that the average dioxin toxicity equivalent concentration in air was 0.105 and 0.055 pg I-TEQ/Nm3 for the first (July-August) and second (October-November) sampling campaign, respectively. The corresponding average dioxin deposition flux in dust was 2.419 and 6.539 ng-I-TEQ/m2/yr, respectively. Both concentration and flux are comparatively lower than those reported elsewhere in the world. Principal component analysis (PCA) of dioxin pattern in air and dust reveals abnormal dioxin concentration and at flux F-site, which was presumably correlated to an unknown neighboring emission source. PCA results of dust reveal area difference but not the air results, which is presumably due to air is more mobile and the composition is more uniform compared to the dust. Large dust (diameter > 2.7 �慆) shows pattern similar to the total dust; whereas small (0.7 �慆 < diameter < 2.7 �慆) presents different pattern. This implies dioxin in dust might come from different sources during the dust formation. The concentration contribution to total dust from small dust is less than 10%.
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