Integrating phase and composition of secondary organic aerosol from the ozonolysis of α-pinene
Integrating phase and composition of secondary organic aerosol from the ozonolysis of α-pinene
复制标题
α-蒎烯臭氧分解二次有机气溶胶的积分相和组成
DOI：
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发表时间：
2014
影响因子：
11.1
通讯作者：
B. Finlayson‐Pitts
中科院分区：
文献类型：
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作者：
C. Kidd;V. Perraud;L. M. Wingen;B. Finlayson‐Pitts
大气气溶胶粒子的相位可以对反应性、生长、氧化和水吸收产生显著影响。因此，它在粒子演化的各个方面都起着关键作用。尽管如此，我们的知识的二次有机气溶胶（SOA）的阶段，以及它如何变化的SOA形成过程中的条件，颗粒的历史，成分，相对湿度和温度仍然很差。最近的实验室实验表明，在某些情况下，SOA最好被描述为半固体或粘性焦油。这项工作显示了如何相/粘度，SOA形成过程中的水的可用性，和组合物是相互关联的，并提供这些关系的机械见解。空气中的颗粒物对公共健康、能见度和气候非常重要。预测其浓度、影响和对控制策略的反应需要其在空气中形成和增长的准确模型。这是具有挑战性的，因为很大一部分是由挥发性有机化合物的复杂反应形成的，产生二次有机气溶胶（SOA），其生长到对能见度、气候和肺中的沉积很重要的尺寸。SOA的生长对颗粒的相/粘度特别敏感，并且仍然知之甚少。我们报告了使用定制设计的撞击器的研究，该撞击器具有作为撞击表面的锗晶体，以研究在297 ± 2 K的相对湿度（RH）高达87%的条件下（这对应于撞击器内部70-86%的最大RH）由α-蒎烯臭氧分解形成的SOA。撞击模式提供了对作为RH函数的相/粘度变化的洞察。衰减全反射-傅里叶变换红外光谱和气溶胶质谱提供了同时与RH的组成变化的信息。结果表明，随着SOA形成的RH增加，粘度降低，伴随着羧酸的贡献增加和高分子量产物的贡献减少。相比之下，干燥形成并随后加湿的SOA在高RH下保持固体。这些研究的结果对模拟SOA在大气中的生长、老化和最终寿命具有重要意义。
Significance The phase of atmospheric aerosol particles can have dramatic effects on reactivity, growth, oxidation, and water uptake. As such, it plays a critical role in every aspect of particle evolution. Despite this, our knowledge of the phase of secondary organic aerosol (SOA) and how it changes in relation to conditions during SOA formation, particle history, composition, relative humidity, and temperature remains poor. Recent laboratory experiments suggest that SOA, under certain circumstances, is best described as a semisolid or viscous tar. This work shows how phase/viscosity, water availability during SOA formation, and composition are interrelated and offers mechanistic insights into these relationships. Airborne particles are important for public health, visibility, and climate. Predicting their concentrations, effects, and responses to control strategies requires accurate models of their formation and growth in air. This is challenging, as a large fraction is formed by complex reactions of volatile organic compounds, generating secondary organic aerosol (SOA), which grows to sizes important for visibility, climate, and deposition in the lung. Growth of SOA is particularly sensitive to the phase/viscosity of the particles and remains poorly understood. We report studies using a custom-designed impactor with a germanium crystal as the impaction surface to study SOA formed from the ozonolysis of α-pinene at relative humidities (RHs) up to 87% at 297 ± 2 K (which corresponds to a maximum RH of 70–86% inside the impactor). The impaction patterns provide insight into changes in phase/viscosity as a function of RH. Attenuated total reflectance-Fourier transform infrared spectroscopy and aerosol mass spectrometry provide simultaneous information on composition changes with RH. The results show that as the RH at which the SOA is formed increases, there is a decrease in viscosity, accompanied by an increasing contribution from carboxylic acids and a decreasing contribution from higher molecular mass products. In contrast, SOA that is formed dry and subsequently humidified remains solid to high RH. The results of these studies have significant implications for modeling the growth, aging, and ultimately, lifetime of SOA in the atmosphere.