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標題: | 探討模擬大氣中黑碳微粒受日照影響之老化過程 The Atmospheric Aging of Black Carbon Particles Induced by Simulated Sunlight |
作者: | Yi-Da Li 李易達 |
指導教授: | 蕭大智(Tai-Chih Hsiao) |
關鍵字: | 黑碳顆粒,交通排放,光化學老化,模擬陽光,煙霧室, black carbon particle,traffic emission,photochemical aging,simulated sunlight,smog chamber, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 交通排放生成的黑碳顆粒為都市中細及超細懸浮微粒的主要來源。由於吸收輻射能量後,能以長波輻射放射的形式釋放能量,黑碳顆粒在影響區域氣象條件以及大氣污染上佔有很重要的角色。在排放進入環境後,黑碳顆粒會持續的與環境中既存的物質交互作用,繼而改變他的微粒構型、吸濕特性、光學特性以及化學組成。這樣的現象被稱之為顆粒物的老化過程。因為顆粒特性的在老化過程中的演變,以及老化過程中對環境影響力的變化,都與顆粒的物化特徵緊密相關,不斷改變的特性進而影響了我們正確預測黑碳顆粒特性演化的準確性。 過去許多文獻使用光化學反應腔,作為研究黑碳顆粒在大氣中老化過程的工具。然而為了能產生快速且明顯的老化現象,過去實驗大多採用紫外光照射,催化反應腔內的二次氣膠生成,並且加入相較於環境中極高濃度的氣體前驅物。但這樣的條件可能無法反映真實環境中所發生的老化現象。因此為了研究在都市地區由陽光照射所引發的黑碳老化現象,我們設計並建立了半近道路環境光化學反應腔。使用氙燈光源作為可調整的模擬陽光,並導入實驗室燃燒產生的黑碳顆粒。藉由氣膠顆粒質量分析儀(APM)、雲凝結核計數器(CCN-100)以及掃描式電移動度粒徑分析儀(SMPS),搭配串聯式體積差分電移動度粒徑分析系統(VT-DMA),我們便能分析黑碳顆粒在老化/披覆過後,以及經熱脫附後的質量、密度、吸濕特性與顆粒構型上的變化。 結果顯示,質量與等效體積粒徑在三個光照強度(0, 472, 978 W/m2)照射後都有提升,對比電移動度僅在強光條件下有變化發生。由體積殘留率、電移動度粒徑以及等效體積粒徑三者的變化推測,我們認為在交通排放環境下的老化過程中,薄披覆的老化條件是較可能發生的結果。有效密度的變化則指出披覆物質的種類會因受光照與否而有所不同。披覆質量通量的結果則顯示披覆層的形成速率會受制於光照強度。而與先前的研究相同,在都市環境中老化的顆粒,因為較的薄的披覆層以及吸濕性低的披覆物質,使得顆粒吸濕性僅有微幅的提升。 Black carbon particles (BCPs) originated traffic emission dominate the aerosol composition in the urban area, especially in megacities. Being able to absorb sunlight and emit radiant energy within the thermal infrared range makes them play an important role in influencing the weather system and atmospheric pollution. Furthermore, BCPs continuously react with various pre-existing matters once they are emitted into the environment, which subsequently leads to changes in their morphology, hygroscopicity, optical and chemical properties. These reactions, as known as particle aging processes further hindered us from correctly characterize the evolution of traffic emitted BCPs since they are tied closely with the physicochemical properties. Numerous studies had been done in discussing the influences of atmospheric aging processes on BCPs properties, in which smog chamber is one of the most general experimental facility. However, most of the present studies were performed under the irradiation of ultraviolet light (UV) and unrealistic high concentration gaseous pollutants. This may deviate the results from real environment scenario. Therefore, to experimentally investigated for BCP aging under urban environment irradiated by natural sunlight, a semi- near road environmental photochemical reaction chamber is designed and established in this study. Xenon lamp is applied as a tunable light source of natural sunlight. BCPs are generated by lab-made butane burner. By employing the aerosol particle mass analyzer (APM; KANOMAX, Japan), cloud condensation nuclei counter (CCN-100; DMT, USA) and scanning mobility particle sizer spectrometer (SMPS; Model 3936; TSI Inc., USA) pairing with the volume tandem differential mobility analyzer (VT-DMA), we can measure the mass, density, hygroscopicity and morphology evolution of the coated BCP and coated-denuded BCP core during the aging process. Mass, consequently volume equivalent diameter (d_ve) have grown under all three of light intensity (0, 472, 978 W/m2) in presenting results, while only limited change of mobility diameter change (Δd_p) in 978 W/m2 irradiance BCP is observed. The result of Volume fraction remain (VFR), Δd_p and d_ve suggesting thinly coated condition might be more common in the aging process of traffic emitted BCPs. Changes in effective density also show different coating material in dark and light-on scenario. Results of coating mass flux show that the coating forming rate is subjected to the light intensity. The limited increase in κ value due to less coating mass and less hydrophilic coating materials is compatible with previous studies. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19765 |
DOI: | 10.6342/NTU202003475 |
全文授權: | 未授權 |
顯示於系所單位: | 環境工程學研究所 |
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