| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 91 === Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are important persistent organic pollutants. Literatures showed that PCDD/Fs exist in the exhaust and fly ash from the municipal waste incinerators (MWIs). Due to the dry/wet deposition and dispersion, PCDD/Fs transfer from stack exhaust into the environmental matrices (such as air, vegetations and soils). Levels of PCDD/Fs in soils can be used to describe long-term exposure. Levels of PCDD/Fs in vegetations can bring information on the short-term exposure.
The aim of this study is to investigate the levels of PCDD/Fs in soil, vegetation and air samples collected in the vicinity of a MWI and compare the patterns of PCDD/F congeners in vegetation, soil, and air, which were collected in the same sampling sites to estimate the dispersion and transformation of environmental matrices. Four sampling sites in the vicinity of the MWI were selected and 4 soil, 4 grass, 4 leaf and 8 air samples were collected at each season. After the extraction and cleanup procedures, the quantification of PCDD/Fs is performed with HRGC/HRMS.
All the samples of soil/vegetation and air at four sites were collected and analyzed completely. During the 3 times collection of air sample, the main wind direction is north wind and the averaged temperature is 29.1℃, 23.5 ℃ and 21.4 ℃, respectively. Average and range of PCDD/Fs levels in soil samples were 5.524(0.486-24.016) pg I-TEQ/g, leaves samples were 4.049(0.823-8.007) pg I-TEQ/g, grasses samples were 1.332(0.224-3.405) pg I-TEQ/g and air samples were 0.114(0.069~0.187) pg I-TEQ/Nm3. Because of soil highly polluted by pentachlorophenol (PCP), levels and patterns of PCDD/Fs collected from Xian-Gong were dissimilar with samples collected from the other three sampling sites. According to the comparison of congener and homologue profiles between particle phase of ambient air samples and soil samples, there are similar congener patterns between particle phase and soil were found in An-Dian, Tu-Cheng and Jian-Gong. It conjectured that soil rebounding dominated the particle phase concentrations of ambient air because of the high wind speed (>2.5 m/s). The levels of soil samples in Xian-Gong were higher than the other two sampling sites. According to the pattern of congeners, soil samples in Xian-Gong and An-Dian may be contaminated by pentachlorophenol and open fire of strew respectively. Comparison of the pattern of congeners in gas phase and leaf revealed that it was similar to most congeners besides OCDD. Guess that the major route of PCDD/Fs transfer to leaves tissue was through the stoma absorption from gas phase PCDD/Fs in the air. Furthermore, the patterns of congeners between air (gas/particle phase) and grass were partially alike. The data shows that grasses absorbed the gaseous PCDFs and the PCDDs in the grass may came from the deposition of airborne particulate.
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