External and internal cloud condensation nuclei (CCN) mixtures: controlled laboratory studies of varying mixing states
External and internal cloud condensation nuclei (CCN) mixtures: controlled laboratory studies of varying mixing states
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DOI：
10.5194/amt-12-4277-2019
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发表时间：
2019-08
影响因子：
3.8
通讯作者：
Diep Vu;Shaokai Gao;Tyler Berte;M. Kacarab;Qi Yao;K. Vafai;A. Asa-Awuku
中科院分区：
文献类型：
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作者：
Diep Vu;Shaokai Gao;Tyler Berte;M. Kacarab;Qi Yao;K. Vafai;A. Asa-Awuku
抽象的。气溶胶化学混合物的变化改变了云凝结核（CCN）的活性。先前的研究已经开发了 CCN 模型，并利用环境现场数据验证了外部和内部混合状态的变化。在这里，我们开发了一种实验方法来测试和验证具有多组分混合物和不同混合状态的已知气溶胶化学成分的 CCN 活化。给出了由一个或多个激活点组成的 CCN 激活曲线。具体来说，在内部、外部和过渡混合条件下生成不同吸湿性的简化双组分系统。针对不同的有机和无机混合物计算了 κ-Köhler 理论预测，并与实验得出的 kappa 值和各自的混合状态进行比较。这项工作采用新颖的实验方法来提供有关受控实验室来源的外部与内部颗粒混合导致的 CCN 激活数据变化的信息。结果表明，由单激活点和双激活点组成的激活曲线分别与内部和外部混合物一致。此外，激活点处平台的高度反映了混合物中外部混合的浓度。平台的存在表明由多个拐点组成的 CCN 激活曲线是具有不同吸水特性的外部混合气溶胶。当在流管中促进混合时，平台消失。在流管实验结束时，气溶胶在内部混合，CCN 激活分数数据可以用单 S 形曲线拟合。模拟外部到内部混合气溶胶的技术适用于具有有机和无机成分的非吸湿性碳质气溶胶。据我们所知，这项工作首次展示了当气溶胶群体在实验室条件下从外部混合状态转变为内部混合状态时，非吸湿性烟灰与吸湿性材料混合的受控 CCN 激活。结果证实，此处和环境数据集中使用的 CCN 激活分析方法是稳健的，可用于推断来源不明的复杂气溶胶成分的混合状态。
Abstract. Changes in aerosol chemical mixtures modify cloud condensation nuclei (CCN) activity. Previous studies have developed CCN models and validated changes in external and internal mixing state with ambient field data. Here, we develop an experimental method to test and validate the CCN activation of known aerosol chemical composition with multicomponent mixtures and varying mixing states. CCN activation curves consisting of one or more activation points are presented. Specifically, simplified two-component systems of varying hygroscopicity were generated under internal, external, and transitional mixing conditions. κ-Köhler theory predictions were calculated for different organic and inorganic mixtures and compared to experimentally derived kappa values and respective mixing states. This work employs novel experimental methods to provide information on the shifts in CCN activation data due to external to internal particle mixing from controlled laboratory sources. Results show that activation curves consisting of single and double activation points are consistent with internal and external mixtures, respectively. In addition, the height of the plateau at the activation points is reflective of the externally mixed concentration in the mixture. The presence of a plateau indicates that CCN activation curves consisting of multiple inflection points are externally mixed aerosols of varying water-uptake properties. The plateau disappears when mixing is promoted in the flow tube. At the end of the flow tube experiment, the aerosols are internally mixed and the CCN activated fraction data can be fit with a single-sigmoid curve. The technique to mimic externally to internally mixed aerosol is applied to non-hygroscopic carbonaceous aerosol with organic and inorganic components. To our knowledge, this work is the first to show controlled CCN activation of mixed non-hygroscopic soot with hygroscopic material as the aerosol population transitions from externally to internally mixed states in laboratory conditions. Results confirm that CCN activation analysis methods used here and in ambient data sets are robust and may be used to infer the mixing state of complex aerosol compositions of unknown origin.