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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Real refractive indices and formation yields of secondary organic aerosol generated from photooxidation of limonene and α-pinene: The effect of the HC/NO _x ratio
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Real refractive indices and formation yields of secondary organic aerosol generated from photooxidation of limonene and α-pinene: The effect of the HC/NO _x ratio

机译：柠檬烯和α-pine烯的光氧化产生的次级有机气溶胶的实际折射率和形成产率：HC / NO _x比的影响

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摘要

The refractive index is an important property affecting aerosol optical properties, which in turn help determine the aerosol direct effect and satellite retrieval results. Here, we investigate the real refractive indices (m _r) of secondary organic aerosols (SOA) generated from the photooxidation of limonene and α-pinene with different HC/NO _x ratios. Refractive indices were obtained from polar nephelometer data using parallel and perpendicular polarized 532 nm light combined with measured size distributions, and retrievals were performed using a genetic algorithm and Mie-Lorenz scattering theory. The absolute error associated with the m _r retrieval is ±0.03, and reliable retrievals are possible for mass concentrations above 5-20 μg/m ~3 depending on particle size. The limonene SOA data suggest the most important factor controlling the refractive index is the HC/NO _x ratio; the refractive index is much less sensitive to the aerosol age or mass concentration. The refractive index ranges from about 1.34 to 1.56 for limonene and from 1.36 to 1.52 for α-pinene, and generally decreases as the HC/NO _x ratio increases. Especially for limonene, the particle diameter is also inversely related to the HC/NO _x ratio; the final size mode increases from 220 to 330 nm as the HC/NO _x ratio decreases from 33 to 6. In an effort to explore the ability of models from the literature to explain the observed refractive indices, a recent limonene oxidation mechanism was combined with SOA partitioning and a structure-property relationship for estimating refractive indices of condensing species. The resulting refractive indices fell in a much narrower range (1.475 ± 0.02) of m _r than observed experimentally. We hypothesize the experimentally observed high m _r values are due to oligomerization and the low values to water uptake, small soluble molecules such as glyoxal and other factors, each of which is not included in the oxidation mechanism. Aerosol formation yields were measured over the mass concentration range from 6 to ～150 μg/m ~3, over which they increased steadily, and were higher for high HC/NO _x ratio experiments.
机译：折射率是影响气溶胶光学特性的重要属性，反过来又有助于确定气溶胶的直接效应和卫星获取结果。在这里，我们研究了由柠檬烯和具有不同HC / NO _x比的α-pine烯的光氧化产生的次级有机气溶胶（SOA）的真实折射率（m _r）。折射率是使用平行和垂直偏振532 nm偏振光结合测得的尺寸分布从偏振比浊仪数据中获得的，并使用遗传算法和Mie-Lorenz散射理论进行检索。与m _r检索相关的绝对误差为±0.03，根据颗粒大小，对于高于5-20μg/ m〜3的质量浓度，可靠的检索是可能的。 mon烯SOA数据表明，控制折射率的最重要因素是HC / NO x比率;折射率对气溶胶年龄或质量浓度的敏感度要低得多。柠檬烯的折射率范围为约1.34至1.56，α-pine烯的折射率范围为1.36至1.52，并且通常随着HC / NO x比率的增加而降低。尤其是对于柠檬烯，粒径也与HC / NO _x比率成反比。随着HC / NO _x比率从33减小到6，最终尺寸模式从220增大到330 nm。为了努力从文献中探索模型解释观测到的折射率的能力，最近将li烯氧化机理与SOA分区和结构性质关系，用于估计冷凝物种的折射率。所得折射率落在m _r的窄得多的范围内（1.475±0.02），比实验观察到的小。我们假设实验观察到的高m _r值是由于低聚和低吸水率，较小的可溶性分子（如乙二醛）和其他因素引起的，而每种因素均未包括在氧化机理中。在6至〜150μg/ m〜3的质量浓度范围内测量了气溶胶生成量，在此范围内，气溶胶生成量稳步增加，而对于高HC / NO _x比实验，则更高。

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