期刊
ATMOSPHERIC ENVIRONMENT
卷 298, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.atmosenv.2023.119625
关键词
Aerosol particles; Surfactant; Hygroscopicity; High relative humidity; Bulk -to -surface partitioning
The hygroscopicity of nanoscale particles containing surfactants was measured using HHTDMA, and a model that comprehensively accounts for the surfactant properties provided the best predictions for the experimental hygroscopicity. This study is important for understanding the hygroscopic characteristics of atmospheric aerosol particles.
For atmospheric aerosol particles, the ubiquitous surfactants can significantly influence their hygroscopicity. However, the hygroscopicity of nanoscale particles containing surfactants are not well understood under sub -saturated conditions, especially at high relative humidity (RH = 90-100%), due to the limitation of traditional instruments and the diversity of surfactants. Here, the hygroscopicity of nanoscale particles composed of a strong surfactant sodium dodecyl sulfate (SDS) and its mixture with ammonium sulfate (AS) was measured using the high humidity tandem differential mobility analyzer (HHTDMA) at RH up to about 99.9%. Three different models based on Ko spacing diaeresis hler theory but different representations of surfactant characteristics were employed to reproduce the measurement outcomes. Results show that SDS particles start gradual hygroscopic growth after RH reaching 97.5%. For SDS-AS mixed particles with 25% w/w SDS, prompt deliquescence and gradual deliques-cence are observed for smaller (20 and 40 nm) and larger particles (100 and 200 nm), respectively. For particles with >= 50% w/w SDS, the onset deliquescence is difficult to found. In general, the model that comprehensively accounts for the surfactant properties including bulk-to-surface partitioning, surface tension reduction, micel-lization and the effect of RH on hygroscopicity parameter, kappa (for SDS-AS particles) provides the best predictions for the experimental hygroscopicity of SDS and SDS-AS particles at subsaturation conditions. Besides, factors affecting the accuracy of theoretical model are discussed in detail. The kappa derived from subsaturated measurement is strongly dependent on RH and dry diameter.
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