Inter-comparison of laboratory smog chamber and flow reactor systems on organic aerosol yield and composition
Inter-comparison of laboratory smog chamber and flow reactor systems on organic aerosol yield and composition
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DOI：
10.5194/amt-8-2315-2015
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发表时间：
2015-01-01
影响因子：
3.8
通讯作者：
Prevot, A. S. H.
中科院分区：
文献类型：
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作者：
Bruns, E. A.;El Haddad, I.;Prevot, A. S. H.
各种各样的工具被用来模拟大气老化，包括烟雾室和流动反应器。传统的大规模烟雾室在数小时至数天的过程中老化排放物，而流动反应器使用高氧化剂浓度快速老化排放物，以达到比烟雾室实验中通常达到的更高的氧化程度。在这种快速氧化下产生的产物与大气的相关性值得进一步研究。然而，以前没有发表的研究已经比较了在流动反应器和烟雾室中从相同的起始混合物产生的产物的产率和化学组成。在烟雾室（SC）和两个流动反应器中由α-蒎烯和木材燃烧排放物的光氧化形成的有机气溶胶的产率和组成：一个潜在的气溶胶质量反应器（PAM）和微烟雾室（MSC），使用气溶胶质谱测定。反应物从SC取样，并在MSC和PAM中使用一系列的羟基自由基（OH）浓度老化，然后在SC中光化学老化。的化学组成，以及最大产量和排放因子，在这两个α-蒎烯和木材燃烧系统确定的PAM和SC的产品同意合理。高OH暴露先前已显示通过破坏碳-碳键并形成较高挥发性物质（其主要存在于气相中）而降低产率;然而，未观察到PAM中的碎片化。使用PAM确定的α-蒎烯系统的产率略低于SC，可能是由于PAM中较高的表面积与体积比导致气相物质的壁损失增加，即使在用采样流与壁的更好隔离抵消时也是如此。MSC的α-蒎烯SOA结果不具有直接可比性，因为颗粒小于最佳AMS透射范围。流动反应器中较高的过饱和度导致比SC中更多的成核。对于木材燃烧系统，从MSC测量的排放因子通常低于从SC测量的排放因子。MSC中较低的排放因子可能是由于在MSC中形成的大量成核模式颗粒（其未被AMS检测到）或由于气体冷凝损失到MSC内部或之后的壁。更全面的覆盖面的潜在粒径范围是需要在未来的SOA测量，以提高我们的理解的差异，产量比较时，MSC SC。PAM和SC同意在测量不确定性的产量和组成的系统和条件研究在这里，这个协议支持继续使用PAM研究大气老化。
A variety of tools are used to simulate atmospheric aging, including smog chambers and flow reactors. Traditional, large-scale smog chambers age emissions over the course of hours to days, whereas flow reactors rapidly age emissions using high oxidant concentrations to reach higher degrees of oxygenation than typically attained in smog chamber experiments. The atmospheric relevance of the products generated under such rapid oxidation warrants further study. However, no previously published studies have compared the yields and chemical composition of products generated in flow reactors and smog chambers from the same starting mixture.The yields and composition of the organic aerosol formed from the photo-oxidation of alpha-pinene and of wood-combustion emissions in a smog chamber (SC) and two flow reactors: a potential aerosol mass reactor (PAM) and a micro-smog chamber (MSC), were determined using aerosol mass spectrometry. Reactants were sampled from the SC and aged in the MSC and the PAM using a range of hydroxyl radical (OH) concentrations and then photo-chemically aged in the SC.The chemical composition, as well as the maximum yields and emission factors, of the products in both the alpha-pinene and wood-combustion systems determined with the PAM and the SC agreed reasonably well. High OH exposures have been shown previously to lower yields by breaking carbon-carbon bonds and forming higher volatility species, which reside largely in the gas phase; however, fragmentation in the PAM was not observed. The yields determined using the PAM for the alpha-pinene system were slightly lower than in the SC, possibly from increased wall losses of gas phase species due to the higher surface area to volume ratios in the PAM, even when offset with better isolation of the sampled flow from the walls. The alpha-pinene SOA results for the MSC were not directly comparable, as particles were smaller than the optimal AMS transmission range. The higher supersaturation in the flow reactors resulted in more nucleation than in the SC. For the wood-combustion system, emission factors measured from the MSC were typically lower than those measured from the SC. Lower emission factors in the MSC may have been due to considerable nucleation mode particles formed in the MSC which were not detected by the AMS or due to condensational loss of gases to the walls inside or after the MSC. More comprehensive coverage of the potential particle size range is needed in future SOA measurements to improve our understanding of the differences in yields when comparing the MSC to the SC. The PAM and the SC agreed within measurement uncertainties in terms of yields and composition for the systems and conditions studied here and this agreement supports the continued use of the PAM to study atmospheric aging.