Multiphase reactivity of polycyclic aromatic hydrocarbons is driven by phase separation and diffusion limitations
| Autor: | Shouming Zhou, Pascale S. J. Lakey, Andreas Zuend, Manabu Shiraiwa, Jonathan P. D. Abbatt, Brian C H Hwang |
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| Rok vydání: | 2019 |
| Předmět: |
animal structures
Ozone 010504 meteorology & atmospheric sciences Diffusion Kinetics Polycyclic aromatic hydrocarbon 010501 environmental sciences complex mixtures 01 natural sciences chemistry.chemical_compound Earth Atmospheric and Planetary Sciences Phase (matter) Squalane indoor chemistry MD Multidisciplinary polycyclic compounds bulk diffusion 0105 earth and related environmental sciences chemistry.chemical_classification Multidisciplinary Ozonolysis phase state kinetic modeling ozone chemistry Chemical engineering 13. Climate action embryonic structures Physical Sciences Pyrene |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America Zhou, Shouming; Hwang, Brian CH; Lakey, Pascale SJ; Zuend, Andreas; Abbatt, Jonathan PD; & Shiraiwa, Manabu. (2019). Multiphase reactivity of polycyclic aromatic hydrocarbons is driven by phase separation and diffusion limitations.. Proceedings of the National Academy of Sciences of the United States of America, 116(24), 11658-11663. doi: 10.1073/pnas.1902517116. UC Irvine: Retrieved from: http://www.escholarship.org/uc/item/7n1608jc |
| ISSN: | 1091-6490 |
| DOI: | 10.1073/pnas.1902517116. |
| Popis: | Significance Polycyclic aromatic hydrocarbons (PAHs) are among the most prominent toxic compounds in the air. Heterogeneous reactions involving O3 can change the toxicity of PAHs, but the reaction mechanism and kinetics remain to be elucidated. Based on new experiments combined with state-of-the-art kinetic and thermodynamic models, we show that phase separation plays a critical role in the ozonolysis of PAHs mixed with secondary organic aerosols and organic oils. Ozonolysis products of PAHs phase separate to form viscous surface crusts, which protect underlying PAHs from ozonolysis to prolong their chemical lifetime. These results have significant implications for outdoor and indoor air quality by affecting PAH long-range transport and fate in indoor environments. Benzo[a]pyrene (BaP), a key polycyclic aromatic hydrocarbon (PAH) often associated with soot particles coated by organic compounds, is a known carcinogen and mutagen. When mixed with organics, the kinetics and mechanisms of chemical transformations of BaP by ozone in indoor and outdoor environments are still not fully elucidated. Using direct analysis in real-time mass spectrometry (DART-MS), kinetics studies of the ozonolysis of BaP in thin films exhibited fast initial loss of BaP followed by a slower decay at long exposure times. Kinetic multilayer modeling demonstrates that the slow decay of BaP over long times can be simulated if there is slow diffusion of BaP from the film interior to the surface, resolving long-standing unresolved observations of incomplete PAH decay upon prolonged ozone exposure. Phase separation drives the slow diffusion time scales in multicomponent systems. Specifically, thermodynamic modeling predicts that BaP phase separates from secondary organic aerosol material so that the BaP-rich layer at the surface shields the inner BaP from ozone. Also, BaP is miscible with organic oils such as squalane, linoleic acid, and cooking oil, but its oxidation products are virtually immiscible, resulting in the formation of a viscous surface crust that hinders diffusion of BaP from the film interior to the surface. These findings imply that phase separation and slow diffusion significantly prolong the chemical lifetime of PAHs, affecting long-range transport of PAHs in the atmosphere and their fates in indoor environments. |
| Databáze: | OpenAIRE |
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