| 摘要: | PM2.5氣膠是我國空氣品質長期關切的指標污染物之一，其來源與組成複雜，持久性自由基(persistent free radicals, PFRs)伴隨在不同微粒尺寸與氣膠化學組成互有關連而有濃度存衰，被視為一種新興環境有害物質，尤與燃燒排放關連，對健康有極大影響。本計畫在代表性地區探知分徑氣膠PFRs存衰濃度潛勢與氣狀前驅物及氣膠化學特性與超細微粒與氣膠數目粒徑分布成果，結合不同空品模式對微粒來源釐清有重要學術貢獻，對環保署釐訂PM2.5空品管制與減量策略及降低國人受PM2.5所致的健康風險具有參考價值。
Taiwan is located between Southeast Asia and East Asia, with a huge load of PM2.5. The causes and contributions of long-range transport and pollution within and outside the country are complex. Persistent free radicals (PFR) in aerosols are highly reactive substances that can persist for extended periods, ranging from days to months or even years. These species are typically associated with aerosols of various sizes and closely linked to the chemical composition of aerosols. PFR represents an emerging class of hazardous substances with significant environmental impacts. Major sources of PFR in aerosols include incomplete combustion of fossil fuels and biomass burning. The chemical composition of atmospheric aerosols varies due to environmental conditions, seasonal changes, and human activities, leading to diverse impacts on health. PFR in aerosols, particularly those generated during combustion processes, may pose greater risks to human health compared to other chemical components in aerosols. This heightened risk is attributed to the high reactivity of PFR, maintaining chemical activity within aerosols. The study focuses on the region of the University. Sample collection occurred during the winter and summer of 2022, with winter samples collected from January to February and summer samples collected from June to July. Water-soluble ions, carboxylates, and saccharides in aerosols were determined using ion chromatography. PFR in aerosols was measured using an electron spin resonance spectrometer (ESR). Throughout the aerosol size ranges, the highest concentrations of PFR consistently occurred in the droplet mode (0.32-2.5 µm). In winter daytime, the concentration was 9.70±3.97×10^14spins/m3, while in winter nighttime, it was 8.87±2.11×10^14spins/m3. Additionally, in summer daytime, the concentration was 4.79±1.93×10^14spins/m3, and in summer nighttime, it was 3.04±1.34×10^14spins/m3. During winter, the concentration peaks of PFR in aerosols were at 1 µm during the day and 1.8 µm at night. In summer, the concentration peaks in aerosols were consistently at 1.8 µm during both day and night. The concentration of PFR in aerosols showed a close correlation with specific chemical components such as levoglucosan, non-sea salt sulfate (nss-sulfate), nss-nitrate, formate, oxalate, and phthalate. This finding suggests that the sources of PFR in aerosols extend beyond biomass burning, encompassing secondary aerosols formed through photochemical processes and other human activities. While levoglucosan has long been considered a biomarker for biomass burning, the high correlation between PFR in aerosols and other chemical components, such as nss-sulfate, nss-nitrate, formate, oxalate, and phthalate, indicates a more diverse origin of PFR in aerosols. This high correlation implies that PFR in aerosols can also form through photochemical reactions involving precursor compounds emitted from various human activities, including industrial processes, transportation, and other combustion sources. The complexity of PFR formation in aerosols and its correlation with multiple chemical components underscore the need for a comprehensive understanding of its sources and pathways. Overall, the high correlation between PFR and specific chemical components in aerosols, beyond biomass burning, highlights the multifaceted nature of PFR sources in aerosols. It emphasizes the importance of considering photochemical processes and secondary aerosols generated from human activities when assessing the environmental impact of PFR. |
