A single-parameter hygroscopicity model for functionalized insoluble aerosol surfaces
A single-parameter hygroscopicity model for functionalized insoluble aerosol surfaces
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DOI：
10.5194/acp-22-13219-2022
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发表时间：
2022-10
影响因子：
6.3
通讯作者：
Chunxia Mao;Kanishk Gohil;A. Asa-Awuku
中科院分区：
文献类型：
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作者：
Chunxia Mao;Kanishk Gohil;A. Asa-Awuku
抽象。分子水平的表面化学对气溶胶吸水和液滴生长的影响还没有得到很好的理解。在这项工作中，球形的，无孔的，单分散的聚苯乙烯胶乳（PSL）颗粒处理不同的表面官能团被用来隔离气溶胶表面化学液滴激活的影响。PSL实际上是水不溶性的，并且颗粒表面的变化可以被认为是水不溶性材料的初始水吸收的关键因素。用云凝结核计数器（CCNC）在过饱和环境中测量了两种表面改性型PSL（PSL-NH 2和PSL-COOH）与普通PSL沿着的液滴生长。比较了传统Köhler（TK）、Flory-Huggins Köhler（FHK）和Frenkel-Halsey-Hill吸附理论（FHH-AT）三种液滴生长模型与实验数据的差异。实验确定的单一吸湿性参数κ在0.002至0.04的范围内。传统的Köhler预测假设拉乌尔定律溶质溶解，低估了PSL颗粒的吸水能力。FHK可以应用于聚合物气溶胶;然而，FHK假设聚合物是可溶的和亲水的。因此，FHK模型产生疏水PSL的阴性结果，并预测与实验观察不一致的非活化行为。FHH-AT模型假设颗粒是水不溶性的，并且可以用两个经验参数（AFHH和BFHH）拟合。FHH-AT模型的预测结果与实验数据吻合较好，并能区分PSL表面改性后颗粒的吸水行为。PSL-NH 2表现出比PSL-COOH稍高的吸湿性，而纯PSL是三者中吸湿性最小的。这一结果与表面官能团的极性及其对水分子的亲和力一致。因此，在AFHH和BFHH的变化可以量化时，表面改性分离的水吸收的研究。当BFHH为1时，PSL-NH 2、PSL-COOH和纯PSL的拟合AFHH为0.23、0.21和0.18。为了简化FHH-AT在云活化模型中的使用，我们还提出并测试了一个新的不溶性化合物的单参数框架κFHH。κFHH与实验数据的一致性在5%以内，可以用于描述具有表面改性性质的水不溶性气溶胶的单参数吸湿性。
Abstract. The impact of molecular level surface chemistry for aerosol water-uptake and droplet growth is not well understood. In this work, spherical, nonporous, monodisperse polystyrene latex (PSL) particles treated with different surface functional groups are exploited to isolate the effects of aerosol surface chemistry for droplet activation. PSL is effectively water insoluble and changes in the particle surface may be considered a critical factor in the initial water uptake of water-insoluble material. The droplet growth of two surface modified types of PSL (PSL-NH2 and PSL-COOH) along with plain PSL was measured in a supersaturated environment with a Cloud Condensation Nuclei Counter (CCNC). Three droplet growth models – traditional Köhler (TK), Flory–Huggins Köhler (FHK) and the Frenkel–Halsey–Hill adsorption theory (FHH-AT) were compared with experimental data. The experimentally determined single hygroscopicity parameter, κ, was found within the range from 0.002 to 0.04. The traditional Köhler prediction assumes Raoult's law solute dissolution and underestimates the water-uptake ability of the PSL particles. FHK can be applied to polymeric aerosol; however, FHK assumes that the polymer is soluble and hydrophilic. Thus, the FHK model generates a negative result for hydrophobic PSL and predicts non-activation behavior that disagrees with the experimental observation. The FHH-AT model assumes that a particle is water insoluble and can be fit with two empirical parameters (AFHH and BFHH). The FHH-AT prediction agrees with the experimental data and can differentiate the water uptake behavior of the particles owing to surface modification of PSL surface. PSL-NH2 exhibits slightly higher hygroscopicity than the PSL-COOH, whereas plain PSL is the least hygroscopic among the three. This result is consistent with the polarity of surface functional groups and their affinity to water molecules. Thus, changes in AFHH and BFHH can be quantified when surface modification is isolated for the study of water-uptake. The fitted AFHH for PSL-NH2, PSL-COOH, and plain PSL is 0.23, 0.21, and 0.18 when BFHH is unity. To simplify the use of FHH-AT for use in cloud activation models, we also present and test a new single parameter framework for insoluble compounds, κFHH. κFHH is within 5 % agreement of the experimental data and can be applied to describe a single-parameter hygroscopicity for water-insoluble aerosol with surface modified properties.