Dataset Information

Glass Transition Temperatures of Organic Mixtures from Isoprene Epoxydiol-Derived Secondary Organic Aerosol.

ABSTRACT: The phase states and glass transition temperatures (T_g) of secondary organic aerosol (SOA) particles are important to resolve for understanding the formation, growth, and fate of SOA as well as their cloud formation properties. Currently, there is a limited understanding of how T_g changes with the composition of organic and inorganic components of atmospheric aerosol. Using broadband dielectric spectroscopy, we measured the T_g of organic mixtures containing isoprene epoxydiol (IEPOX)-derived SOA components, including 2-methyltetrols (2-MT), 2-methyltetrol-sulfate (2-MTS), and 3-methyltetrol-sulfate (3-MTS). The results demonstrate that the T_g of mixtures depends on their composition. The Kwei equation, a modified Gordon-Taylor equation with an added quadratic term and a fitting parameter representing strong intermolecular interactions, provides a good fit for the T_g-composition relationship of complex mixtures. By combining Raman spectroscopy with geometry optimization simulations obtained using density functional theory, we demonstrate that the non-linear deviation of T_g as a function of composition may be caused by changes in the extent of hydrogen bonding in the mixture.

SUBMITTER: Chen B

PROVIDER: S-EPMC10863072 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature

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Glass Transition Temperatures of Organic Mixtures from Isoprene Epoxydiol-Derived Secondary Organic Aerosol.

Chen Bo B Mirrielees Jessica A JA Chen Yuzhi Y Onasch Timothy B TB Zhang Zhenfa Z Gold Avram A Surratt Jason D JD Zhang Yue Y Brooks Sarah D SD

The journal of physical chemistry. A 20230502 18

The phase states and glass transition temperatures (Tg) of secondary organic aerosol (SOA) particles are important to resolve for understanding the formation, growth, and fate of SOA as well as their cloud formation properties. Currently, there is a limited understanding of how Tg changes with the composition of organic and inorganic components of atmospheric aerosol. Using broadband dielectric spectroscopy, we measured the Tg of organic mixt ...[more]

PMID: 37129903

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Project description:The nitrate radical (NO3) oxidation of isoprene is an important contributor to secondary organic aerosol (SOA). Isoprene has two double bonds which allow for multigeneration oxidation to occur. The effects of multigeneration chemistry on the gas- and particle-phase product distributions of the isoprene + NO3 system are not fully understood. In this study, we conduct chamber experiments by varying the ratio of N2O5 (precursor of NO3) to isoprene concentration from 1:1 to 14:1 to investigate the formation of products in both phases under different oxidation levels. Multigeneration chemistry leads to the formation of gas-phase products which then partition into particle phase depending on the product volatility; first-generation products (15-36% of total SOA) such as C5H9NO5 and C10H16N2O9 have volatility (log10C* = 1.0-3.0 using the partitioning method and log10C* = 2.6-4.5 using the formula method) 1-5 orders of magnitude higher than second-generation products (37-57% of total SOA, log10C* = -0.8-2.1 using the partitioning method and log10C* = -3.7-1.8 using the formula method) such as C5H8,10N2O8, C5H9N3O10, and C10H17N3O13. The fast reaction rate constants of first-generation products (estimated to be on the order of 10-13 cm3 molecules-1 s-1 at 295 K) and the lower volatility of second-generation products result in increased SOA yields when NO3 availability increases and multigeneration chemistry is enhanced. Specifically, an increase of up to 300% in SOA yield is observed when the N2O5/isoprene ratio increases from 1:1 to 3:1; from 5.7% (organic aerosol mass concentration, ΔM o = 4.2 μg/m3) to 16.3% (ΔM o = 11.9 μg/m3) when the reacted isoprene concentration is 25 ppb and from 3.1% (ΔM o = 1.2 μg/m3) to 12.4% (ΔM o = 5.4 μg/m3) when the reacted isoprene concentration is 15 ppb. The maximum SOA yield occurs when the N2O5/isoprene ratio is greater than or equal to 3:1 as a combined result of multigeneration chemistry and peroxy radicals (RO2) fate. We encourage future studies to consider both factors, which can vary under different laboratory and ambient conditions, when comparing SOA yields to better understand any differences observed. Our results highlight that multigeneration chemistry and the updated parameters including reaction rate constants and volatility distribution of products should be considered to enable a more comprehensive representation and prediction of SOA formation from NO3 oxidation of isoprene in atmospheric models.

Dataset Information

Glass Transition Temperatures of Organic Mixtures from Isoprene Epoxydiol-Derived Secondary Organic Aerosol.

Publications

Glass Transition Temperatures of Organic Mixtures from Isoprene Epoxydiol-Derived Secondary Organic Aerosol.

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