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Polycatechol and polyguaiacol are light-absorbing and water-insoluble particles that efficiently form from iron-catalyzed reactions with aromatic compounds from biomass burning emissions. Little quantitative information is known about their water uptake and cloud or haze droplet formation ability. In this study, polycatechol and polyguaiacol particles were synthesized in the laboratory, and their cloud condensation nucleation efficiencies were investigated under sub- and supersaturated relative humidity (RH) conditions using a hygroscopicity tandem differential mobility analyzer (H-TDMA) and a cloud condensation nuclei counter (CCNC), respectively. Experimental results show that both polymeric materials are slightly hygroscopic and that their single hygroscopicity parameter ( κ ) ranges from 0.03 to 0.25, which is within the κ range for secondary organic aerosols (SOA). Polycatechol is more hygroscopic than polyguaiacol, which is explained by differences in their structure. Polyguaiacol has similar water uptake as other insoluble organic compounds, and droplet formation is modelled well with Brunauer–Emmett–Teller (BET) or Frankel Hill Hershey-Adsorption Isotherm theory (FHH-AT). Both polymeric materials are not strongly surface active in range of 0.5 to 30 g L −1 , and thus differences in subsaturated and supersaturated hygroscopicity measurement are not attributed to the presence of surface-active materials. Instead, it is due to the solubility limits of both chemicals and H-TDMA being driven by water adsorption. The implications of these results are discussed in the context of aerosol–cloud interactions from the hygroscopicity of aerosols from primary and secondary sources.
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Hybrid Water Adsorption and Solubility Partitioning for Aerosol Hygroscopicity and Droplet Growth
In this work, we studied the Cloud Condensation nuclei (CCN) activity and subsaturated droplet growth of Phthalic acid (PTA), isophthalic acid, (IPTA) and terephthalic acid (TPTA), significant benzene polycarboxylic acids and structural isomers found in the atmosphere. Köhler Theory can be effectively applied for hygroscopicity analysis of PTA due to its higher aqueous solubility compared to IPTA and TPTA. As with other hygroscopicity studies of partially water-soluble and effectively water insoluble species, the supersaturated and subsaturated hygroscopicity derived from (KT) principles do not agree. To address the disparities in the sub- and supersaturated droplet growth, we developed a new analytical framework called the Hybrid Activity Model (HAM). HAM incorporates the aqueous solubility of a solute within an adsorption-based activation framework. Frenkel-Halsey-Hill (FHH)-Adsorption Theory (FHH-AT) was combined with the aqueous solubility of the compound to develop HAM. Analysis from HAM was validated using laboratory measurements of pure PTA, IPTA, TPTA and PTA-IPTA internal mixtures. Furthermore, the results generated using HAM were tested against traditional KT and FHH-AT to compare their water uptake predictive capabilities. A single-hygroscopicity parameter was also developed based on the HAM framework. Results show that the HAM based hygroscopicity parameter based can successfully simulate the water uptake behavior of the pure and internally mixed samples. Results indicate that the HAM framework may be applied to atmospheric aerosols of varying chemical structures and aqueous solubility.
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- PAR ID:
- 10335467
- Date Published:
- Journal Name:
- Atmospheric chemistry and physics discussion
- ISSN:
- 1680-7375
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi.org/10.5194/acp-2022-346
