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15.4: Fabrication of 5.5‐inch AMOLED Panel using IGZO TFTs
摘要： Naphthalene (Nap) and methylnaphthalene (MN) are the most abundant polycyclic aromatic hydrocarbons (PAHs) in atmosphere and have been proposed to be important precursors of anthropogenic secondary organic aerosol (SOA) derived from laboratory chamber experiments. In this study, atmospheric Nap/MN and their gas-phase photooxidation products were quanti?ed by a Proton Transfer Reaction-Quadrupole interface Time-of-Flight Mass Spectrometer (PTR-QiTOF) during the 2016 winter in Beijing. Phthalic anhydride, a late generation product from Nap under high-NOx conditions, appeared to be more prominent than 2-formylcinnamaldehyde (early generation product), possibly due to more su?cient oxidation during the haze. 1,2-Phthalic acid (1,2-PhA), the hydrated form of phthalic anhydride, was capable of partitioning into aerosol phase and served as a tracer to explore the contribution of Nap to ambient SOA. The measured fraction in particle phase (Fp) of 1,2-PhA averaged at 73 ± 13% with OA mass loadings of 52.5?87.8 μg/m3, lower than the value predicted by the absorptive partitioning model (100%). Using tracer product-based and precursor consumption-based methods, 2-ring PAHs (Nap and MN) were estimated to produce 14.9% (an upper limit) of the SOA formed in the afternoon during the wintertime haze, suggesting a comparable contribution of Nap and MN with monocyclic-aromatics on urban SOA formation.
关键词： PTR-QiTOF,Secondary Organic Aerosol,Beijing,Haze Events,Naphthalene,Methylnaphthalene
更新于2025-09-11 14:15:04
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Collection efficiency of <i>α</i>-pinene secondary organic aerosol particles explored via light-scattering single-particle aerosol mass spectrometry
摘要： We investigated the collection ef?ciency and effective ionization ef?ciency for secondary organic aerosol (SOA) particles made from α-pinene + O3 using the single-particle capabilities of the aerosol mass spectrometer (AMS). The mean count-based collection ef?ciency (CEp) for SOA across these experiments is 0.30 (±0.04 SD), ranging from 0.25 to 0.40. The mean mass-based collection ef?ciency (CEm) is 0.49 (±0.07 SD). This sub-unit collection ef?ciency and delayed vaporization is attributable to particle bounce in the vaporization region. Using the coupled optical and chemical detection of the light-scattering single-particle (LSSP) module of the AMS, we provide clear evidence that “delayed vaporization” is somewhat of a misnomer for these particles: SOA particles measured as a part of the AMS mass distribution do not vaporize at a slow rate; rather, they ?ash-vaporize, albeit often not on the initial impact with the vaporizer but instead upon a subsequent impact with a hot surface in the vaporization region. We also ?nd that the effective ionization ef?ciency (de?ned as ions per particle, IPP) decreases with delayed arrival time. CEp is not a function of particle size (for the mobility diameter range investigated, 170–460 nm), but we did see a decrease in CEp with thermodenuder temperature, implying that oxidation state and/or volatility can affect CEp for SOA. By measuring the mean ions per particle produced for monodisperse particles as a function of signal delay time, we can separately determine CEp and CEm and thus more accurately measure the relative ionization ef?ciency (compared to ammonium nitrate) of different particle types.
关键词： aerosol mass spectrometer,collection efficiency,α-pinene,ionization efficiency,delayed vaporization,particle bounce,secondary organic aerosol
更新于2025-09-04 15:30:14
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Impact of molecular structure on secondary organic aerosol formation from aromatic hydrocarbon photooxidation under low NO<sub><i>x</i></sub> conditions
摘要： The molecular structure of volatile organic compounds (VOC) determines their oxidation pathway, directly impacting secondary organic aerosol (SOA) formation. This study comprehensively investigates the impact of molecular structure on SOA formation from the photooxidation of twelve different eight to nine carbon aromatic hydrocarbons under low NOx conditions. The effects of the alkyl substitute number, location, carbon chain length and branching structure on the photooxidation of aromatic hydrocarbons are demonstrated by analyzing SOA yield, chemical composition and physical properties. Aromatic hydrocarbons, categorized into five groups, show a yield order of ortho (o-xylene and o-ethyltoluene) > one substitute (ethylbenzene, propylbenzene and isopropylbenzene) > meta (m-xylene and m-ethyltoluene) > three substitute (trimethylbenzenes) > para (p-xylene and p-ethyltoluene). SOA yields of aromatic hydrocarbon photooxidation do not monotonically decrease when increasing alkyl substitute number. The ortho position promotes SOA formation while the para position suppresses aromatic oxidation and SOA formation. Observed SOA chemical composition and volatility confirm that higher yield is associated with further oxidation. SOA chemical composition also suggests that aromatic oxidation increases with increasing alkyl substitute chain length and branching structure. Further, carbon dilution theory developed by Li et al. (2015a) is extended in this study to serve as a standard method to determine the extent of oxidation of an alkyl substituted aromatic hydrocarbon.
关键词： photooxidation,low NOx conditions,molecular structure,secondary organic aerosol,aromatic hydrocarbons
更新于2025-09-04 15:30:14