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Cummings BE, Shiraiwa M, Waring MS. Phase state of organic aerosols may limit temperature-driven thermodynamic repartitioning following outdoor-to-indoor transport. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2022; 24:1678-1696. [PMID: 35920302 DOI: 10.1039/d2em00093h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ambient aerosols often experience temperature and humidity gradients following outdoor-to-indoor transport, causing organic aerosols (OA) to either gain or lose mass via gas-particle repartitioning. Recent models have sought to quantify these effects using equilibrium partitioning thermodynamics. However, evidence suggests some indoor OA may possess glassy or semisolid phase states with higher viscosities than liquid OA. Characteristic partitioning timescales of higher-viscosity particles are significantly longer than for liquid particles, which may either fully or partially inhibit repartitioning. For outdoor OA experiencing a temperature change during transport indoors, the ultimate repartitioning state depends on the relationship between the gas-particle partitioning rate coefficient (kgp) of semivolatile organics and the indoor particle loss rate coefficient (lp). That is, thermodynamic equilibrium partitioning may occur when semivolatile kgp ≫ lp, no repartitioning when semivolatile kgp ≪ lp, and partial repartitioning when their magnitudes are similar. Longer indoor particle lifetimes, higher particle number, and larger particle sizes all raise kgp (driving repartitioning towards equilibrium). For simulated U.S. residences, equilibrium condensation was likely reached in humid climate zones during warm meteorological conditions. In colder regions, the degree of evaporative repartitioning depended on whether organics could repartition before the particle phase state adjusts to indoor conditions, which is uncertain. When an appreciable temperature gradient exists, this study not only confirmed that all outdoor-originating OA that is liquid indoors will reach thermodynamic equilibrium, but also concluded that a plurality (46% for this domain) of such OA that is semisolid may also achieve thermodynamic equilibrium during its indoor lifetime.
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Bellcross A, Bé AG, Geiger FM, Thomson RJ. Molecular Chirality and Cloud Activation Potentials of Dimeric α-Pinene Oxidation Products. J Am Chem Soc 2021; 143:16653-16662. [PMID: 34605643 DOI: 10.1021/jacs.1c07509] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The surface activity of ten atmospherically relevant α-pinene-derived dimers having varying terminal functional groups and backbone stereochemistry is reported. We find ∼10% differences in surface activity between diastereomers of the same dimer, demonstrating that surface activity depends upon backbone stereochemistry. Octanol-water (KOW) and octanol-ammonium sulfate partitioning coefficient (KOAS) measurements of our standards align well with the surface activity measurements, with the more surface-active dimers exhibiting increased hydrophobicity. Our findings establish a link between molecular chirality and cloud activation potential of secondary organic aerosol particles. Given the diurnal variations in enantiomeric excess of biogenic emissions, possible contributions of such a link to biosphere:atmosphere feedbacks as well as aerosol particle viscosity and phase separation are discussed.
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Affiliation(s)
- Aleia Bellcross
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Ariana Gray Bé
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Franz M Geiger
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Regan J Thomson
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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Ingram S, Rovelli G, Song YC, Topping D, Dutcher CS, Liu S, Nandy L, Shiraiwa M, Reid JP. Accurate Prediction of Organic Aerosol Evaporation Using Kinetic Multilayer Modeling and the Stokes-Einstein Equation. J Phys Chem A 2021; 125:3444-3456. [PMID: 33861595 DOI: 10.1021/acs.jpca.1c00986] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Organic aerosol can adopt a wide range of viscosities, from liquid to glass, depending on the local humidity. In highly viscous droplets, the evaporation rates of organic components are suppressed to varying degrees, yet water evaporation remains fast. Here, we examine the coevaporation of semivolatile organic compounds (SVOCs), along with their solvating water, from aerosol particles levitated in a humidity-controlled environment. To better replicate the composition of secondary aerosol, nonvolatile organics were also present, creating a three-component diffusion problem. Kinetic modeling reproduced the evaporation accurately when the SVOCs were assumed to obey the Stokes-Einstein relation, and water was not. Crucially, our methodology uses previously collected data to constrain the time-dependent viscosity, as well as water diffusion coefficients, allowing it to be predictive rather than postdictive. Throughout the study, evaporation rates were found to decrease as SVOCs deplete from the particle, suggesting path function type behavior.
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Affiliation(s)
- Stephen Ingram
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Grazia Rovelli
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Young-Chul Song
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - David Topping
- Department of Earth and Environmental Sciences, University of Manchester, Oxford Rd, Manchester M13 9PL, U.K
| | - Cari S Dutcher
- Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States.,Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, United States
| | - Shihao Liu
- Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States
| | - Lucy Nandy
- Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States
| | - Manabu Shiraiwa
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Jonathan P Reid
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
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Rossich Molina E, Gerber RB. Microscopic Mechanisms of N 2O 5 Hydrolysis on the Surface of Water Droplets. J Phys Chem A 2020; 124:224-228. [PMID: 31829595 DOI: 10.1021/acs.jpca.9b08900] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reactions of N2O5, in particular heterogeneous hydrolysis, play a vital role in determining the chemistry of the atmosphere. The N2O5 heterogeneous hydrolysis reaction has been the subject of extensive research for decades, yet the physicochemical details of the mechanism have not been established. In this study, we show that this reaction can occur on the surface of a pure water droplet. We compute a relevant transition state for a nano-size model system and follow its evolution in time by means of ab initio molecular dynamics. This transition state, where N2O5 has a strong ion-pair character, leads directly to HNO3. Both electrophilic and nucleophilic mechanisms take place. It is suggested that corresponding simulations for hydrolysis in the bulk are desirable.
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Affiliation(s)
- Estefanía Rossich Molina
- The Institute of Chemistry and the Fritz Haber Center for Molecular Dynamics , The Hebrew University , Jerusalem 9190401 , Israel
| | - R Benny Gerber
- The Institute of Chemistry and the Fritz Haber Center for Molecular Dynamics , The Hebrew University , Jerusalem 9190401 , Israel.,Department of Chemistry , University of California , Irvine , California 92697 , United States
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Finlayson‐Pitts BJ. Multiphase chemistry in the troposphere: It all starts … and ends … with gases. INT J CHEM KINET 2019. [DOI: 10.1002/kin.21305] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Multiphase reactivity of polycyclic aromatic hydrocarbons is driven by phase separation and diffusion limitations. Proc Natl Acad Sci U S A 2019; 116:11658-11663. [PMID: 31142653 PMCID: PMC6575172 DOI: 10.1073/pnas.1902517116] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
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.
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Wingen LM, Finlayson-Pitts BJ. Probing surfaces of atmospherically relevant organic particles by easy ambient sonic-spray ionization mass spectrometry (EASI-MS). Chem Sci 2018; 10:884-897. [PMID: 30774883 PMCID: PMC6346289 DOI: 10.1039/c8sc03851a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 11/01/2018] [Indexed: 12/12/2022] Open
Abstract
EASI-MS is a promising technique for probing the chemical structures of inhomogeneous airborne organic particles.
Both ambient and laboratory-generated particles can have a surface composition different from the bulk, but there are currently few analytical techniques available to probe these differences. Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) was applied to solid, laboratory-generated particles with core–shell morphologies formed from a variety of dicarboxylic acids. The soft ionization facilitated parent peak detection for the two compounds, from which the depth probed could be determined from the relative signal intensities. Two different configurations of a custom-made nebulizer are reported that yield different probe depths. In the “orthogonal mode,” with the nebulizer ∼10 centimeters away from the particle stream and at a 90° angle to the MS inlet, evaporation of the nebulizer droplets forms ions before interaction with the particles. The probe depth for orthogonal mode EASI-MS is shown to be 2–4 nm in these particle systems. In the “droplet mode”, the nebulizer and particle streams are in close proximity to each other and the MS inlet so that the particles interact with charged liquid droplets. This configuration resulted in full dissolution of the particles and gives particle composition similar to that from collection on filters and extraction of the particles (bulk). These studies establish that EASI-MS is a promising technique for probing the chemical structures of inhomogeneous airborne organic particles.
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Affiliation(s)
- L M Wingen
- Department of Chemistry , University of California Irvine , Irvine , CA 92697-2025 , USA . ; Tel: +1-949-824-7670
| | - B J Finlayson-Pitts
- Department of Chemistry , University of California Irvine , Irvine , CA 92697-2025 , USA . ; Tel: +1-949-824-7670
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