1
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Bain A, Lalemi L, Croll Dawes N, Miles REH, Prophet AM, Wilson KR, Bzdek BR. Surfactant Partitioning Dynamics in Freshly Generated Aerosol Droplets. J Am Chem Soc 2024; 146:16028-16038. [PMID: 38822805 PMCID: PMC11177314 DOI: 10.1021/jacs.4c03041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 06/03/2024]
Abstract
Aerosol droplets are unique microcompartments with relevance to areas as diverse as materials and chemical synthesis, atmospheric chemistry, and cloud formation. Observations of highly accelerated and unusual chemistry taking place in such droplets have challenged our understanding of chemical kinetics in these microscopic systems. Due to their large surface-area-to-volume ratios, interfacial processes can play a dominant role in governing chemical reactivity and other processes in droplets. Quantitative knowledge about droplet surface properties is required to explain reaction mechanisms and product yields. However, our understanding of the compositions and properties of these dynamic, microscopic interfaces is poor compared to our understanding of bulk processes. Here, we measure the dynamic surface tensions of 14-25 μm radius (11-65 pL) droplets containing a strong surfactant (either sodium dodecyl sulfate or octyl-β-D-thioglucopyranoside) using a stroboscopic imaging approach, enabling observation of the dynamics of surfactant partitioning to the droplet-air interface on time scales of 10s to 100s of microseconds after droplet generation. The experimental results are interpreted with a state-of-the-art kinetic model accounting for the unique high surface-area-to-volume ratio inherent to aerosol droplets, providing insights into both the surfactant diffusion and adsorption kinetics as well as the time-dependence of the interfacial surfactant concentration. This study demonstrates that microscopic droplet interfaces can take up to many milliseconds to reach equilibrium. Such time scales should be considered when attempting to explain observations of accelerated chemistry in microcompartments.
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Affiliation(s)
- Alison Bain
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
- Department
of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - Lara Lalemi
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Nathan Croll Dawes
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Rachael E. H. Miles
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Alexander M. Prophet
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Kevin R. Wilson
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Bryan R. Bzdek
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
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2
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Wilson KR, Prophet AM. Chemical Kinetics in Microdroplets. Annu Rev Phys Chem 2024; 75:185-208. [PMID: 38382571 DOI: 10.1146/annurev-physchem-052623-120718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Micrometer-sized compartments play significant roles in driving heterogeneous transformations within atmospheric and biochemical systems as well as providing vehicles for drug delivery and novel reaction environments for the synthesis of industrial chemicals. Many reports now indicate that reaction kinetics are accelerated under microconfinement, for example, in sprays, thin films, droplets, aerosols, and emulsions. These observations are dramatic, posing a challenge to our understanding of chemical reaction mechanisms with potentially significant practical consequences for predicting the complex chemistry in natural systems. Here we introduce the idea of kinetic confinement, which is intended to provide a conceptual backdrop for understanding when and why microdroplet reaction kinetics differ from their macroscale analogs.
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Affiliation(s)
- Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA;
| | - Alexander M Prophet
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA;
- Department of Chemistry, University of California, Berkeley, California, USA;
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3
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Lei Z, Chen B, Brooks SD. Effect of Acidity on Ice Nucleation by Inorganic-Organic Mixed Droplets. ACS EARTH & SPACE CHEMISTRY 2023; 7:2562-2573. [PMID: 38148991 PMCID: PMC10749479 DOI: 10.1021/acsearthspacechem.3c00242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 11/08/2023] [Accepted: 11/27/2023] [Indexed: 12/28/2023]
Abstract
Aerosol acidity significantly influences heterogeneous chemical reactions and human health. Additionally, acidity may play a role in cloud formation by modifying the ice nucleation properties of inorganic and organic aerosols. In this work, we combined our well-established ice nucleation technique with Raman microspectroscopy to study ice nucleation in representative inorganic and organic aerosols across a range of pH conditions (pH -0.1 to 5.5). Homogeneous nucleation was observed in systems containing ammonium sulfate, sulfuric acid, and sucrose. In contrast, droplets containing ammonium sulfate mixed with diethyl sebacate, poly(ethylene glycol) 400, and 1,2,6-hexanetriol were found to undergo liquid-liquid phase separation, exhibiting core-shell morphologies with observed initiation of heterogeneous freezing in the cores. Our experimental findings demonstrate that an increased acidity reduces the ice nucleation ability of droplets. Changes in the ratio of bisulfate to sulfate coincided with shifts in ice nucleation temperatures, suggesting that the presence of bisulfate may decrease the ice nucleation efficiency. We also report on how the morphology and viscosity impact ice nucleation properties. This study aims to enhance our fundamental understanding of acidity's effect on ice nucleation ability, providing context for the role of acidity in atmospheric ice cloud formation.
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Affiliation(s)
- Ziying Lei
- Department of Atmospheric
Science, Texas A&M University, College Station, Texas 77843, United States
| | - Bo Chen
- Department of Atmospheric
Science, Texas A&M University, College Station, Texas 77843, United States
| | - Sarah D. Brooks
- Department of Atmospheric
Science, Texas A&M University, College Station, Texas 77843, United States
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4
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Brown EK, Rovelli G, Wilson KR. pH jump kinetics in colliding microdroplets: accelerated synthesis of azamonardine from dopamine and resorcinol. Chem Sci 2023; 14:6430-6442. [PMID: 37325131 PMCID: PMC10266468 DOI: 10.1039/d3sc01576a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 05/21/2023] [Indexed: 06/17/2023] Open
Abstract
Recent studies report the dramatic acceleration of chemical reactions in micron-sized compartments. In the majority of these studies the exact acceleration mechanism is unknown but the droplet interface is thought to play a significant role. Dopamine reacts with resorcinol to form a fluorescent product azamonardine and is used as a model system to examine how droplet interfaces accelerate reaction kinetics. The reaction is initiated by colliding two droplets levitated in a branched quadrupole trap, which allows the reaction to be observed in individual droplets where the size, concentration, and charge are carefully controlled. The collision of two droplets produces a pH jump and the reaction kinetics are quantified optically and in situ by measuring the formation of azamonardine. The reaction was observed to occur 1.5 to 7.4 times faster in 9-35 micron droplets compared to the same reaction conducted in a macroscale container. A kinetic model of the experimental results suggests that the acceleration mechanism arises from both the more rapid diffusion of oxygen into the droplet, as well as increased reagent concentrations at the air-water interface.
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Affiliation(s)
- Emily K Brown
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA +1 510-495-2474
- Department of Chemistry, University of California Berkeley CA 94720 USA
| | - Grazia Rovelli
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA +1 510-495-2474
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA +1 510-495-2474
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5
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Zhang W, Zhao Z, Shen C, Zhang H. Unexpectedly Efficient Aging of Organic Aerosols Mediated by Autoxidation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:6965-6974. [PMID: 37083304 DOI: 10.1021/acs.est.2c09773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Multiphase oxidative aging is a ubiquitous process for atmospheric organic aerosols (OA). But its kinetics was often found to be slow in previous laboratory studies where high hydroxyl radical concentrations ([•OH]) were used. In this study, we performed heterogeneous oxidation experiments of several model OA systems under varied aging timescales and gas-phase [•OH]. Our results suggest that OA heterogeneous oxidation may be 2-3 orders of magnitude faster when [•OH] is decreased from typical laboratory flow tube conditions to atmospheric levels. Direct laboratory mass spectrometry measurements coupled with kinetic simulations suggest that an intermolecular autoxidation mechanism mediated by particle-phase peroxy radicals greatly accelerates OA oxidation, with enhanced formation of organic hydroperoxides, alcohols, and fragmentation products. With autoxidation, we estimate that the OA oxidation timescale in the atmosphere may be from less than a day to several days. Thus, OA oxidative aging can have greater atmospheric impacts than previously expected. Furthermore, our findings reveal the nature of heterogeneous aerosol oxidation chemistry in the atmosphere and help improve the understanding and prediction of atmospheric OA aging and composition evolution.
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Affiliation(s)
- Wen Zhang
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Zixu Zhao
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Chuanyang Shen
- Department of Chemistry, University of California, Riverside, California 92507, United States
| | - Haofei Zhang
- Department of Chemistry, University of California, Riverside, California 92507, United States
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6
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Witkowski B, al-Sharafi M, Błaziak K, Gierczak T. Aging of α-Pinene Secondary Organic Aerosol by Hydroxyl Radicals in the Aqueous Phase: Kinetics and Products. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:6040-6051. [PMID: 37014140 PMCID: PMC10116591 DOI: 10.1021/acs.est.2c07630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 03/20/2023] [Accepted: 03/20/2023] [Indexed: 06/19/2023]
Abstract
The reaction of hydroxyl radicals (OH) with a water-soluble fraction of the α-pinene secondary organic aerosol (SOA) was investigated using liquid chromatography coupled with negative electrospray ionization mass spectrometry. The SOA was generated by the dark ozonolysis of α-pinene, extracted into the water, and subjected to chemical aging by the OH. Bimolecular reaction rate coefficients (kOH) for the oxidation of terpenoic acids by the OH were measured using the relative rate method. The unaged SOA was dominated by the cyclobutyl-ring-retaining compounds, primarily cis-pinonic, cis-pinic, and hydroxy-pinonic acids. Aqueous oxidation by the OH resulted in the removal of early-stage products and dimers, including well-known oligomers with MW = 358 and 368 Da. Furthermore, a 2- to 5-fold increase in the concentration of cyclobutyl-ring-opening products was observed, including terpenylic and diaterpenylic acids and diaterpenylic acid acetate as well as some of the newly identified OH aging markers. At the same time, results obtained from the kinetic box model showed a high degree of SOA fragmentation following the reaction with the OH, which indicates that non-radical reactions occurring during the evaporation of water likely contribute to the high yields of terpenoic aqSOAs reported previously. The estimated atmospheric lifetimes showed that in clouds, terpenoic acids react with the OH exclusively in the aqueous phase. Aqueous OH aging of the α-pinene SOA results in a 10% increase of the average O/C ratio and a 3-fold decrease in the average kOH value, which is likely to affect the cloud condensation nuclei activity of the aqSOA formed after the evaporation of water.
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7
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West CP, Morales AC, Ryan J, Misovich MV, Hettiyadura APS, Rivera-Adorno F, Tomlin JM, Darmody A, Linn BN, Lin P, Laskin A. Molecular investigation of the multi-phase photochemistry of Fe(III)-citrate in aqueous solution. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2023; 25:190-213. [PMID: 35634912 DOI: 10.1039/d1em00503k] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Iron (Fe) is ubiquitous in nature and found as FeII or FeIII in minerals or as dissolved ions Fe2+ or Fe3+ in aqueous systems. The interactions of soluble Fe have important implications for fresh water and marine biogeochemical cycles, which have impacts on global terrestrial and atmospheric environments. Upon dissolution of FeIII into natural aquatic systems, organic carboxylic acids efficiently chelate FeIII to form [FeIII-carboxylate]2+ complexes that undergo a wide range of photochemistry-induced radical reactions. The chemical composition and photochemical transformations of these mixtures are largely unknown, making it challenging to estimate their environmental impact. To investigate the photochemical process of FeIII-carboxylates at the molecular level, we conduct a comprehensive experimental study employing UV-visible spectroscopy, liquid chromatography coupled to photodiode array and high-resolution mass spectrometry detection, and oil immersion flow microscopy. In this study, aqueous solutions of FeIII-citrate were photolyzed under 365 nm light in an experimental setup with an apparent quantum yield of (φ) ∼0.02, followed by chemical analyses of reacted mixtures withdrawn at increment time intervals of the experiment. The apparent photochemical reaction kinetics of Fe3+-citrates (aq) were expressed as two generalized consecutive reactions of with the experimental rate constants of j1 ∼ 0.12 min-1 and j2 ∼ 0.05 min-1, respectively. Molecular characterization results indicate that R and I consist of both water-soluble organic and Fe-organic species, while P compounds are a mixture of water-soluble and colloidal materials. The latter were identified as Fe-carbonaceous colloids formed at long photolysis times. The carbonaceous content of these colloids was identified as unsaturated organic species with low oxygen content and carbon with a reduced oxidation state, indicative of their plausible radical recombination mechanism under oxygen-deprived conditions typical for the extensively photolyzed mixtures. Based on the molecular characterization results, we discuss the comprehensive reaction mechanism of FeIII-citrate photochemistry and report on the formation of previously unexplored colloidal reaction products, which may contribute to atmospheric and terrestrial light-absorbing materials in aquatic environments.
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Affiliation(s)
- Christopher P West
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | - Ana C Morales
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | - Jackson Ryan
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | - Maria V Misovich
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | | | | | - Jay M Tomlin
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | - Andrew Darmody
- Department of Aeronautics and Aerospace Engineering, Purdue University, West Lafayette, IN, USA
| | - Brittany N Linn
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | - Peng Lin
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
| | - Alexander Laskin
- Department of Chemistry, Purdue University, West Lafayette, IN, 47906, USA.
- Department of Earth, Atmospheric & Planetary Sciences, Purdue University, West Lafayette, IN, USA
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8
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Shen C, Zhang W, Choczynski J, Davies JF, Zhang H. Phase State and Relative Humidity Regulate the Heterogeneous Oxidation Kinetics and Pathways of Organic-Inorganic Mixed Aerosols. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:15398-15407. [PMID: 36306431 DOI: 10.1021/acs.est.2c04670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Inorganic species always coexist with organic materials in atmospheric particles and may influence the heterogeneous oxidation of organic aerosols. However, very limited studies have explored the role of the inorganics in the chemical evolution of organic species in mixed aerosols. This study examines the heterogeneous oxidation of glutaric acid-ammonium sulfate and 1,2,6-hexanetriol-ammonium sulfate aerosols by hydroxyl radicals (OH) under varied organic mass fractions (forg) and relative humidity in a flow tube reactor. Coupling the oxidation kinetics and product measurements with kinetic model simulations, we found that under both low relative humidity (RH, 30-35%) and high RH conditions (85%), the decreased forg from 0.7 to 0.2 accelerates the oxidation of the organic materials by a factor of up to 11. We suggest that the faster oxidation kinetics under low-RH conditions is due to full or partial phase separation, with the organics greatly enriched at the particle outer region, while enhanced "salting-out" of the organics and OH adsorption caused by higher inorganics could explain the observations under high-RH conditions. Analysis of the oxidation products reveals that the dilution of organics by the inorganic salts and corresponding water uptake under high-RH conditions will favor alkoxy radical fragmentation by a factor of 3-4 and inhibit its secondary chain propagation chemistry. Our results suggest that atmospheric organic aerosol oxidation lifetime and composition are strongly impacted by the coexistent inorganic salts.
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Affiliation(s)
- Chuanyang Shen
- Department of Chemistry, University of California, Riverside, California92507, United States
| | - Wen Zhang
- Department of Chemistry, University of California, Riverside, California92507, United States
| | - Jack Choczynski
- Department of Chemistry, University of California, Riverside, California92507, United States
| | - James F Davies
- Department of Chemistry, University of California, Riverside, California92507, United States
| | - Haofei Zhang
- Department of Chemistry, University of California, Riverside, California92507, United States
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9
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Wilson KR, Prophet AM, Willis MD. A Kinetic Model for Predicting Trace Gas Uptake and Reaction. J Phys Chem A 2022; 126:7291-7308. [PMID: 36170058 DOI: 10.1021/acs.jpca.2c03559] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A model is developed to describe trace gas uptake and reaction with applications to aerosols and microdroplets. Gas uptake by the liquid is formulated as a coupled equilibria that links gas, surface, and bulk regions of the droplet or solution. Previously, this framework was used in explicit stochastic reaction-diffusion simulations to predict the reactive uptake kinetics of ozone with droplets containing aqueous aconitic acid, maleic acid, and sodium nitrite. With the use of prior data and simulation results, a new equation for the uptake coefficient is derived, which accounts for both surface and bulk reactions. Lambert W functions are used to obtain closed form solutions to the integrated rate laws for the multiphase kinetics; similar to previous expressions that describe Michaelis-Menten enzyme kinetics. Together these equations couple interface and bulk processes over a wide range of conditions and do not require many of the limiting assumptions needed to apply resistor model formulations to explain trace gas uptake and reaction.
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Affiliation(s)
- Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Alexander M Prophet
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Megan D Willis
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
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10
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Soto XL, Swierk JR. Using Lifetime and Quenching Rate Constant to Determine Optimal Quencher Concentration. ACS OMEGA 2022; 7:25532-25536. [PMID: 35910131 PMCID: PMC9330265 DOI: 10.1021/acsomega.2c02638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Excited state quenching is a key step in photochemical reactions that involve energy or electron transfer. High reaction quantum yields require sufficiently high concentrations of a quencher to ensure efficient quenching. The determination of quencher concentrations is typically done through trial and error. Using kinetic modeling, however, a simple relationship was developed that predicts the concentration of quencher necessary to quench 90% of excited states, using only the photosensitizer lifetime and the rate constant for quenching as inputs. Comparison of the predicted quencher concentrations and quencher concentrations used in photoredox reactions featuring acridinium-based photocatalysts reveals that the majority of reactions used quencher concentrations significantly below the predicted concentration. This suggests that these reactions exhibit low quantum yields, requiring long reaction times and/or intense light sources.
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Affiliation(s)
- Xena L. Soto
- Department
of Chemistry, State University of New York
at Binghamton, 4400 Vestal
Parkway East, P.O. Box 6000, Vestal, New York 13850, United
States
- Department
of Chemistry, Lehman College/City University
of New York, 250 Bedford
Park Boulevard West, Bronx, New York 10468, United
States
| | - John R. Swierk
- Department
of Chemistry, State University of New York
at Binghamton, 4400 Vestal
Parkway East, P.O. Box 6000, Vestal, New York 13850, United
States
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11
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Willis MD, Wilson KR. Coupled Interfacial and Bulk Kinetics Govern the Timescales of Multiphase Ozonolysis Reactions. J Phys Chem A 2022; 126:4991-5010. [PMID: 35863113 DOI: 10.1021/acs.jpca.2c03059] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Chemical transformations in aerosols impact the lifetime of particle phase species, the fate of atmospheric pollutants, and both climate- and health-relevant aerosol properties. Timescales for multiphase reactions of ozone in atmospheric aqueous phases are governed by coupled kinetic processes between the gas phase, the particle interface, and its bulk, which respond dynamically to reactive consumption of O3. However, models of atmospheric aerosol reactivity often do not account for the coupled nature of multiphase processes. To examine these dynamics, we use new and prior experimental observations of aqueous droplet reaction kinetics, including three systems with a range of surface affinities and ozonolysis rate coefficients (trans-aconitic acid (C6H6O6), maleic acid (C4H4O4), and sodium nitrite (NaNO2)). Using literature rate coefficients and thermodynamic properties, we constrain a simple two-compartment stochastic kinetic model which resolves the interface from the particle bulk and represents O3 partitioning, diffusion, and reaction as a coupled kinetic system. Our kinetic model accurately predicts decay kinetics across all three systems, demonstrating that both the thermodynamic properties of O3 and the coupled kinetic and diffusion processes are key to making accurate predictions. An enhanced concentration of adsorbed O3, compared to gas and bulk phases is rapidly maintained and remains constant even as O3 is consumed by reaction. Multiphase systems dynamically seek to achieve equilibrium in response to reactive O3 loss, but this is hampered at solute concentrations relevant to aqueous aerosol by the rate of O3 arrival in the bulk by diffusion. As a result, bulk-phase O3 becomes depleted from its Henry's law solubility. This bulk-phase O3 depletion limits reaction timescales for relatively slow-reacting organic solutes with low interfacial affinity (i.e., trans-aconitic and maleic acids, with krxn ≈ 103-104 M-1 s-1), which is in contrast to fast-reacting solutes with higher surface affinity (i.e., nitrite, with krxn ≈ 105 M-1 s-1) where surface reactions strongly impact the observed decay kinetics.
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Affiliation(s)
- Megan D Willis
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, United States
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12
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Wei J, Fang T, Shiraiwa M. Effects of Acidity on Reactive Oxygen Species Formation from Secondary Organic Aerosols. ACS ENVIRONMENTAL AU 2022; 2:336-345. [PMID: 35928555 PMCID: PMC9342606 DOI: 10.1021/acsenvironau.2c00018] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Reactive oxygen species (ROS) play a critical role in the chemical transformation of atmospheric secondary organic aerosols (SOA) and aerosol health effects by causing oxidative stress in vivo. Acidity is an important physicochemical property of atmospheric aerosols, but its effects on the ROS formation from SOA have been poorly characterized. By applying the electron paramagnetic resonance spin-trapping technique and the Diogenes chemiluminescence assay, we find highly distinct radical yields and composition at different pH values in the range of 1-7.4 from SOA generated by oxidation of isoprene, α-terpineol, α-pinene, β-pinene, toluene, and naphthalene. We observe that isoprene SOA has substantial hydroxyl radical (•OH) and organic radical yields at neutral pH, which are 1.5-2 times higher compared to acidic conditions in total radical yields. Superoxide (O2 •-) is found to be the dominant species generated by all types of SOAs at lower pH. At neutral pH, α-terpineol SOA exhibits a substantial yield of carbon-centered organic radicals, while no radical formation is observed by aromatic SOA. Further experiments with model compounds show that the decomposition of organic peroxide leading to radical formation may be suppressed at lower pH due to acid-catalyzed rearrangement of peroxides. We also observe 1.5-3 times higher molar yields of hydrogen peroxide (H2O2) in acidic conditions compared to neutral pH by biogenic and aromatic SOA, likely due to enhanced decomposition of α-hydroxyhydroperoxides and quinone redox cycling, respectively. These findings are critical to bridge the gap in understanding ROS formation mechanisms and kinetics in atmospheric and physiological environments.
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13
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Ahmed M, Blum M, Crumlin EJ, Geissler PL, Head-Gordon T, Limmer DT, Mandadapu KK, Saykally RJ, Wilson KR. Molecular Properties and Chemical Transformations Near Interfaces. J Phys Chem B 2021; 125:9037-9051. [PMID: 34365795 DOI: 10.1021/acs.jpcb.1c03756] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The properties of bulk water and aqueous solutions are known to change in the vicinity of an interface and/or in a confined environment, including the thermodynamics of ion selectivity at interfaces, transition states and pathways of chemical reactions, and nucleation events and phase growth. Here we describe joint progress in identifying unifying concepts about how air, liquid, and solid interfaces can alter molecular properties and chemical reactivity compared to bulk water and multicomponent solutions. We also discuss progress made in interfacial chemistry through advancements in new theory, molecular simulation, and experiments.
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Affiliation(s)
- Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Monika Blum
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ethan J Crumlin
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Phillip L Geissler
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Teresa Head-Gordon
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - David T Limmer
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Kranthi K Mandadapu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Richard J Saykally
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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14
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Moreira AJ, Freschi CD, Pereira EC, Freschi GPG. N-compounds speciation analysis in environmental samples using ultrasound-assisted solid-liquid extraction and non-chromatographic techniques. ENVIRONMENTAL MONITORING AND ASSESSMENT 2021; 193:297. [PMID: 33893885 DOI: 10.1007/s10661-021-09088-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 04/19/2021] [Indexed: 06/12/2023]
Abstract
A fast, efficient, and non-chromatographic method was presented in this study for nitrite, nitrate, and p-nitrophenol (N-compounds) extraction and speciation analysis of environmental samples. By applying ultrasound-assisted solid-liquid extraction (USLE), analytes were efficiently extracted from water, soil, or sediment collected in areas of environmental disaster. These analytes were selectively converted to NO(g) through UV photolysis (NO3-), H2O2/UV photocatalysis (PNP), and direct conversion (NO2-). Following conversion, NO(g) was separated from the liquid phase and determined by high-resolution continuum source molecular absorption spectrometry (HR-CS MAS). The LODs obtained were 0.097 ± 0.004 mg L-1 for nitrite, 0.119 ± 0.004 mg L-1 for nitrate, and 0.090 ± 0.006 mg L-1 for p-nitrophenol. On applying this speciation method to environmental samples, concentrations were found to be up to 0.99 ± 0.03 mg L-1 (NO2-), 49.80 ± 2.5 mg L-1 (NO3-), and 0.10 ± 0.02 mg L-1 (PNP). Finally, addition/recovery study of real water, soil, and sediment samples showed 101 ± 2% recovery for NO2-, 100 ± 1% for NO3-, and 96 ± 5% for PNP.
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Affiliation(s)
- Ailton José Moreira
- LAFFEQ, Institute of Science and Technology, Federal University of Alfenas, UNIFAL-MG, Poços de Caldas, MG, 37715-400, Brazil.
- Chemistry Dept, Universidade Federal de São Carlos, UFSCar-SP, São Carlos, SP, 13565-905, Brazil.
| | - Carolina Dakuzaku Freschi
- LAFFEQ, Institute of Science and Technology, Federal University of Alfenas, UNIFAL-MG, Poços de Caldas, MG, 37715-400, Brazil
| | - Ernesto Chaves Pereira
- Chemistry Dept, Universidade Federal de São Carlos, UFSCar-SP, São Carlos, SP, 13565-905, Brazil
| | - Gian Paulo Giovanni Freschi
- LAFFEQ, Institute of Science and Technology, Federal University of Alfenas, UNIFAL-MG, Poços de Caldas, MG, 37715-400, Brazil
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15
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Houle FA, Miles REH, Pollak CJ, Reid JP. A purely kinetic description of the evaporation of water droplets. J Chem Phys 2021; 154:054501. [PMID: 33557551 DOI: 10.1063/5.0037967] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The process of water evaporation, although deeply studied, does not enjoy a kinetic description that captures known physics and can be integrated with other detailed processes such as drying of catalytic membranes embedded in vapor-fed devices and chemical reactions in aerosol whose volumes are changing dynamically. In this work, we present a simple, three-step kinetic model for water evaporation that is based on theory and validated by using well-established thermodynamic models of droplet size as a function of time, temperature, and relative humidity as well as data from time-resolved measurements of evaporating droplet size. The kinetic mechanism for evaporation is a combination of two limiting processes occurring in the highly dynamic liquid-vapor interfacial region: direct first order desorption of a single water molecule and desorption resulting from a local fluctuation, described using third order kinetics. The model reproduces data over a range of relative humidities and temperatures only if the interface that separates bulk water from gas phase water has a finite width, consistent with previous experimental and theoretical studies. The influence of droplet cooling during rapid evaporation on the kinetics is discussed; discrepancies between the various models point to the need for additional experimental data to identify their origin.
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Affiliation(s)
- Frances A Houle
- Joint Center for Artificial Photosynthesis and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Rachael E H Miles
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Connor J Pollak
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Jonathan P Reid
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
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16
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Wilson KR, Prophet AM, Rovelli G, Willis MD, Rapf RJ, Jacobs MI. A kinetic description of how interfaces accelerate reactions in micro-compartments. Chem Sci 2020; 11:8533-8545. [PMID: 34123113 PMCID: PMC8163377 DOI: 10.1039/d0sc03189e] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A kinetic expression is derived to explain how interfaces alter bulk chemical equilibria and accelerate reactions in micro-compartments. This description, aided by the development of a stochastic model, quantitatively predicts previous experimental observations of accelerated imine synthesis in micron-sized emulsions. The expression accounts for how reactant concentration and compartment size together lead to accelerated reaction rates under micro-confinement. These rates do not depend solely on concentration, but rather the fraction of total molecules in the compartment that are at the interface. Although there are ∼107 to 1013 solute molecules in a typical micro-compartment, a kind of "stochasticity" appears when compartment size and reagent concentration yield nearly equal numbers of bulk and interfacial molecules. Although this is distinct from the stochasticity produced by nano-confinement, these results show how interfaces can govern chemical transformations in larger atmospheric, geologic and biological compartments.
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Affiliation(s)
- Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Alexander M Prophet
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA .,Department of Chemistry, University of California Berkeley CA 94720 USA
| | - Grazia Rovelli
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Megan D Willis
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Rebecca J Rapf
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Michael I Jacobs
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign Urbana Illinois 61801 USA
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17
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Zhao Z, Tolentino R, Lee J, Vuong A, Yang X, Zhang H. Interfacial Dimerization by Organic Radical Reactions during Heterogeneous Oxidative Aging of Oxygenated Organic Aerosols. J Phys Chem A 2019; 123:10782-10792. [PMID: 31765152 DOI: 10.1021/acs.jpca.9b10779] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxidative aging of atmospheric organic aerosols (OA) substantially modifies their chemical compositions, physical properties, and hence the various environmental impacts. Here, we report observations of a previously unrecognized process leading to dimer formation during heterogeneous •OH-initiated oxidative aging of oxygenated OA. Isomer-resolved ion mobility mass spectrometry measurements and reaction-diffusion kinetic simulations are in good agreement, elucidating new mechanisms of dimerization by organic radical (i.e., peroxy and alkoxy radicals) cross reactions using glutaric acid as a surrogate oxygenated OA. These radical reactions are predicted to occur more prominently near the gas-particle interface following oxidation, especially in diffusion-limited viscous OA particles. Chemical structure analysis shows that esters dominate the detected dimers, followed by organic peroxides and ethers, highlighting the importance of acyl peroxy and acyloxy radicals. Simulations suggest that the reported dimer formation through the new interfacial mechanism could be appreciable under both laboratory and ambient conditions. Therefore, the dimers that are formed and enriched at the gas-particle interface are expected to play a crucial role in the effective reactivity, volatility, viscosity, and hygroscopicity of aged OA particles.
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Affiliation(s)
- Zixu Zhao
- Department of Chemistry , University of California at Riverside , Riverside , California 92521 , United States
| | - Ricardo Tolentino
- Department of Chemistry , University of California at Riverside , Riverside , California 92521 , United States
| | - Jennifer Lee
- Department of Chemistry , University of California at Riverside , Riverside , California 92521 , United States
| | - Austin Vuong
- Department of Molecular, Cell, and Systems Biology , University of California at Riverside , Riverside , California 92521 , United States
| | - Xiaoyan Yang
- Department of Environmental Sciences , University of California at Riverside , Riverside , California 92521 , United States
| | - Haofei Zhang
- Department of Chemistry , University of California at Riverside , Riverside , California 92521 , United States
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18
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Alpert PA, Corral Arroyo P, Dou J, Krieger UK, Steimer SS, Förster JD, Ditas F, Pöhlker C, Rossignol S, Passananti M, Perrier S, George C, Shiraiwa M, Berkemeier T, Watts B, Ammann M. Visualizing reaction and diffusion in xanthan gum aerosol particles exposed to ozone. Phys Chem Chem Phys 2019; 21:20613-20627. [PMID: 31528972 DOI: 10.1039/c9cp03731d] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Atmospheric aerosol particles with a high viscosity may become inhomogeneously mixed during chemical processing. Models have predicted gradients in condensed phase reactant concentration throughout particles as the result of diffusion and chemical reaction limitations, termed chemical gradients. However, these have never been directly observed for atmospherically relevant particle diameters. We investigated the reaction between ozone and aerosol particles composed of xanthan gum and FeCl2 and observed the in situ chemical reaction that oxidized Fe2+ to Fe3+ using X-ray spectromicroscopy. Iron oxidation state of particles as small as 0.2 μm in diameter were imaged over time with a spatial resolution of tens of nanometers. We found that the loss off Fe2+ accelerated with increasing ozone concentration and relative humidity, RH. Concentric 2-D column integrated profiles of the Fe2+ fraction, α, out of the total iron were derived and demonstrated that particle surfaces became oxidized while particle cores remained unreacted at RH = 0-20%. At higher RH, chemical gradients evolved over time, extended deeper from the particle surface, and Fe2+ became more homogeneously distributed. We used the kinetic multi-layer model for aerosol surface and bulk chemistry (KM-SUB) to simulate ozone reaction constrained with our observations and inferred key parameters as a function of RH including Henry's Law constant for ozone, HO3, and diffusion coefficients for ozone and iron, DO3 and DFe, respectively. We found that HO3 is higher in our xanthan gum/FeCl2 particles than for water and increases when RH decreased from about 80% to dry conditions. This coincided with a decrease in both DO3 and DFe. In order to reproduce observed chemical gradients, our model predicted that ozone could not be present further than a few nanometers from a particle surface indicating near surface reactions were driving changes in iron oxidation state. However, the observed chemical gradients in α observed over hundreds of nanometers must have been the result of iron transport from the particle interior to the surface where ozone oxidation occurred. In the context of our results, we examine the applicability of the reacto-diffusive framework and discuss diffusion limitations for other reactive gas-aerosol systems of atmospheric importance.
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Affiliation(s)
- Peter A Alpert
- Laboratory of Environmental Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
| | - Pablo Corral Arroyo
- Laboratory of Environmental Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. and Institute for Physical Chemistry, ETH Zürich, 8092 Zürich, Switzerland
| | - Jing Dou
- Institute for Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
| | - Ulrich K Krieger
- Institute for Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
| | - Sarah S Steimer
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Jan-David Förster
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Florian Ditas
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Christopher Pöhlker
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Stéphanie Rossignol
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON, F-69626, Villeurbanne, France and Aix Marseille Université, CNRS, LCE UMR 7376, 13331 Marseille, France
| | - Monica Passananti
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON, F-69626, Villeurbanne, France and Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, 00710, Helsinki, Finland and Dipartimento di Chimica, Università di Torino, Via Giuria 5, 10125 Torino, Italy
| | - Sebastien Perrier
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON, F-69626, Villeurbanne, France
| | - Christian George
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON, F-69626, Villeurbanne, France
| | - Manabu Shiraiwa
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Thomas Berkemeier
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany and School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Benjamin Watts
- Laboratory for Synchrotron Radiation-Condensed Matter, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Markus Ammann
- Laboratory of Environmental Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
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19
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Houle FA, Wiegel AA, Wilson KR. Predicting Aerosol Reactivity Across Scales: from the Laboratory to the Atmosphere. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:13774-13781. [PMID: 30412390 DOI: 10.1021/acs.est.8b04688] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
To fully utilize the results of laboratory-based studies of the chemistry of model atmospheric aerosol reactions, it is important to understand how to relate them to the conditions found in nature. In this study, we have taken a validated reaction-diffusion mechanism for oxidation of C30H62 aerosol by OH under flow tube conditions and examined its predictions for another experimental regime (continuous flow stirred tank reactor) and for the atmosphere, spanning alkane aerosol viscosities from liquid to semisolid. The results show that under OH-concentration-limited and aerosol-mixing-limited conditions, it should be possible to select laboratory experimental conditions where many aspects of the particle phase and volatile product chemistry under atmospheric conditions can be revealed. If the OH collision and organic diffusion rates are comparable, however, reactivity is highly sensitive to the details of both OH concentration and internal mixing. The characteristics of the transition between limiting conditions provide key insights into which parts of the reaction mechanism dominate in the various kinetic regimes.
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Affiliation(s)
- Frances A Houle
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , 1 Cyclotron Road , Berkeley , California 94720 , United States
| | - Aaron A Wiegel
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , 1 Cyclotron Road , Berkeley , California 94720 , United States
| | - Kevin R Wilson
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , 1 Cyclotron Road , Berkeley , California 94720 , United States
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20
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Craig RL, Peterson PK, Nandy L, Lei Z, Hossain MA, Camarena S, Dodson RA, Cook RD, Dutcher CS, Ault AP. Direct Determination of Aerosol pH: Size-Resolved Measurements of Submicrometer and Supermicrometer Aqueous Particles. Anal Chem 2018; 90:11232-11239. [DOI: 10.1021/acs.analchem.8b00586] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
| | | | - Lucy Nandy
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | | | | | | | | | | | - Cari S. Dutcher
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
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21
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Witkowski B, Jurdana S, Gierczak T. Limononic Acid Oxidation by Hydroxyl Radicals and Ozone in the Aqueous Phase. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:3402-3411. [PMID: 29444406 DOI: 10.1021/acs.est.7b04867] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Kinetics and mechanism of limononic acid (3-isopropenyl-6-oxoheptanoic acid, LA) oxidation by hydroxyl radicals (OH) and ozone (O3) were studied in the aqueous phase at 298 ± 2 K. These reactions were investigated using liquid chromatography coupled to the electrospray ionization and quadrupole tandem mass spectrometry (LC-ESI/MS/MS). The rate coefficients determined for LA + OH reaction were: 1.3 ± 0.3 × 1010 M-1 s-1 at pH = 2 and 5.7 ± 0.6 × 109 M-1 s-1 at pH = 10. The rate coefficient determined for LA ozonolysis was 4.2 ± 0.2 × 104 M-1 s-1 at pH = 2. The calculated Henry's law constant (H) for LA was ca. 6.3 × 106 M × atm-1, thereby indicating that in fogs and clouds with LWC = 0.3-0.5 g × m-3 LA will reside entirely in the aqueous phase. Calculated atmospheric lifetimes due to reaction with OH and O3 strongly indicate that aqueous-phase oxidation can be important for LA under realistic atmospheric conditions. Under acidic conditions, the aqueous-phase oxidation of LA by OH will dominate over reaction with O3, whereas the opposite is more likely when pH ≥ 4.5. The aqueous-phase oxidation of LA produced keto-limononic acid and a number of low-volatility products, such as hydroperoxy-LA and α-hydroxyhydroperoxides.
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Affiliation(s)
- Bartłomiej Witkowski
- University of Warsaw , Faculty of Chemistry , Al. Żwirki i Wigury 101 , 02-089 Warsaw , Poland
| | - Sara Jurdana
- University of Warsaw , Faculty of Chemistry , Al. Żwirki i Wigury 101 , 02-089 Warsaw , Poland
| | - Tomasz Gierczak
- University of Warsaw , Faculty of Chemistry , Al. Żwirki i Wigury 101 , 02-089 Warsaw , Poland
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22
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Heine N, Houle FA, Wilson KR. Connecting the Elementary Reaction Pathways of Criegee Intermediates to the Chemical Erosion of Squalene Interfaces during Ozonolysis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:13740-13748. [PMID: 29120614 DOI: 10.1021/acs.est.7b04197] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Criegee intermediates (CI), formed in alkene ozonolysis, are central for controlling the multiphase chemistry of organic molecules in both indoor and outdoor environments. Here, we examine the heterogeneous ozonolysis of squalene, a key species in indoor air chemistry. Aerosol mass spectrometry is used to investigate how the ozone (O3) concentration, relative humidity (RH), and particle size control reaction rates and mechanisms. Although the reaction rate is found to be independent of RH, the reaction products and particle size depend upon H2O. Under dry conditions (RH = 3%) the reaction produces high-molecular-weight secondary ozonides (SOZ), which are known skin irritants, and a modest change in particle size. Increasing the RH reduces the aerosol size by 30%, while producing mainly volatile aldehyde products, increases potential respiratory exposure. Chemical kinetics simulations link the elementary reactions steps of CI to the observed kinetics, product distributions, and changes in particle size. The simulations reveal that ozonolysis occurs near the surface and is O3-transport limited. The observed secondary ozonides are consistent with the formation of mainly secondary CI, in contrast to gas-phase ozonolysis mechanisms.
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Affiliation(s)
- Nadja Heine
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Frances A Houle
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
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