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Title: Regional-Scale Modeling Parameterizations for Secondary Organic Aerosol Formation from Isoprene Epoxydiols: Experimentally Based Evaluation and Optimization

Journal Article · · ACS ES&T Air

Isoprene is an abundant volatile organic compound emitted from broadleaf forests. Under low nitric oxide concentrations, isoprene is photochemically oxidized to form gas-phase isoprene epoxydiols (IEPOX). In the presence of acidified sulfate aerosols, IEPOX enhances the secondary organic aerosol (SOA) formation. Predictions of IEPOX-SOA in regional-scale models, e.g., the Community Multiscale Air Quality Model (CMAQ), are uncertain due to homogeneous aerosol assumptions, underpredictions of water uptake (hygroscopicity), and aerosol surface area. Here, we used experimental measurements of IEPOX-SOA tracers, 2-methyltetrols (2-MT) and 2-methyltetrol sulfates (2-MTS), formed at initial IEPOX-to-inorganic sulfate ratios ranging from 1–10.5, at ∼50% relative humidity to constrain key IEPOX-SOA parameters: phase separation, organic shell diffusivity (Dorg), acidity, hygroscopic growth, mass accommodation, and kinetics. The base CMAQ parametrization overpredicted experimental IEPOX-SOA with an average normalized mean bias (NMBaverage) of 1.63. CMAQ with phase separation underpredicted IEPOX-SOA (NMBaverage = −0.71). Using the phase-separated model, CMAQ model performance was optimized (NMBaverage = 0.077) with an increased Dorg = 2 × 10–16 m2s–1 and increased rate constants (k2-MT = 1 × 10–3 M2 s–1, k2-MTS = 8.83 × 10–3 M2 s–1). The optimized model explicitly accounted for hygroscopic growth by utilizing experimentally derived growth rates, improving aerosol surface area predictions. Our model highlights the importance of the aerosol mixing state (homogeneous versus phase-separated), aerosol size dynamics, and hygroscopic growth in modeling heterogeneous reactive uptake of IEPOX.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE
Grant/Contract Number:
AC05-76RL01830
OSTI ID:
3029100
Report Number(s):
PNNL-SA-211243
Journal Information:
ACS ES&T Air, Journal Name: ACS ES&T Air Journal Issue: 11 Vol. 2; ISSN 2837-1402
Publisher:
ACS PublicationsCopyright Statement
Country of Publication:
United States
Language:
English

References (70)

Recent advances in understanding secondary organic aerosol: Implications for global climate forcing: Advances in Secondary Organic Aerosol journal June 2017
Chemical characterization of secondary organic aerosol constituents from isoprene ozonolysis in the presence of acidic aerosol journal April 2016
Gas-Phase Reactions of Isoprene and Its Major Oxidation Products journal February 2018
Natural and Anthropogenically Influenced Isoprene Oxidation in Southeastern United States and Central Amazon journal April 2020
Decreases in Epoxide-Driven Secondary Organic Aerosol Production under Highly Acidic Conditions: The Importance of Acid–Base Equilibria journal June 2024
Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA journal February 2016
Simulating Aqueous-Phase Isoprene-Epoxydiol (IEPOX) Secondary Organic Aerosol Production During the 2013 Southern Oxidant and Aerosol Study (SOAS) journal April 2017
Isomerization of Second-Generation Isoprene Peroxy Radicals: Epoxide Formation and Implications for Secondary Organic Aerosol Yields journal April 2017
Assessing the Potential Mechanisms of Isomerization Reactions of Isoprene Epoxydiols on Secondary Organic Aerosol journal June 2018
Increasing Isoprene Epoxydiol-to-Inorganic Sulfate Aerosol Ratio Results in Extensive Conversion of Inorganic Sulfate to Organosulfur Forms: Implications for Aerosol Physicochemical Properties journal June 2019
The Cooling Rate- and Volatility-Dependent Glass-Forming Properties of Organic Aerosols Measured by Broadband Dielectric Spectroscopy journal September 2019
The C5–Alkene Triol Conundrum: Structural Characterization and Quantitation of Isoprene-Derived C5H10O3 Reactive Uptake Products journal September 2022
Effect of the Aerosol-Phase State on Secondary Organic Aerosol Formation from the Reactive Uptake of Isoprene-Derived Epoxydiols (IEPOX) journal February 2018
Glass Transition Temperatures of Organic Mixtures from Isoprene Epoxydiol-Derived Secondary Organic Aerosol journal May 2023
Seasonal Contribution of Isoprene-Derived Organosulfates to Total Water-Soluble Fine Particulate Organic Sulfur in the United States journal August 2021
Morphology and Viscosity Changes after Reactive Uptake of Isoprene Epoxydiols in Submicrometer Phase Separated Particles with Secondary Organic Aerosol Formed from Different Volatile Organic Compounds journal March 2022
Tight Coupling of Surface and In-Plant Biochemistry and Convection Governs Key Fine Particulate Components over the Amazon Rainforest journal January 2022
Observationally Constrained Modeling of the Reactive Uptake of Isoprene-Derived Epoxydiols under Elevated Relative Humidity and Varying Acidity of Seed Aerosol Conditions journal March 2023
Hygroscopicity Depends on Aerosol Acidity and Sulfate Content during the Reactive Uptake of Isoprene Epoxydiols journal August 2025
Joint Impacts of Acidity and Viscosity on the Formation of Secondary Organic Aerosol from Isoprene Epoxydiols (IEPOX) in Phase Separated Particles journal October 2019
Applying a Phase-Separation Parameterization in Modeling Secondary Organic Aerosol Formation from Acid-Driven Reactive Uptake of Isoprene Epoxydiols under Humid Conditions journal April 2024
Isoprene Epoxydiols as Precursors to Secondary Organic Aerosol Formation: Acid-Catalyzed Reactive Uptake Studies with Authentic Compounds journal November 2011
Real-Time Continuous Characterization of Secondary Organic Aerosol Derived from Isoprene Epoxydiols in Downtown Atlanta, Georgia, Using the Aerodyne Aerosol Chemical Speciation Monitor journal May 2013
Epoxide Pathways Improve Model Predictions of Isoprene Markers and Reveal Key Role of Acidity in Aerosol Formation journal September 2013
Reactive Uptake of an Isoprene-Derived Epoxydiol to Submicron Aerosol Particles journal September 2014
Heterogeneous Reactions of Isoprene-Derived Epoxides: Reaction Probabilities and Molar Secondary Organic Aerosol Yield Estimates journal January 2015
Chemical Composition of Secondary Organic Aerosol Formed from the Photooxidation of Isoprene journal August 2006
On the Reactive Uptake of Gaseous Compounds by Organic-Coated Aqueous Aerosols:  Theoretical Analysis and Application to the Heterogeneous Hydrolysis of N 2 O 5 journal September 2006
Kinetics and Products of the Acid-Catalyzed Ring-Opening of Atmospherically Relevant Butyl Epoxy Alcohols journal August 2010
Modeling the formation of secondary organic aerosol within a comprehensive air quality model system journal November 2001
Development and Evaluation of Chemistry‐Aerosol‐Climate Model CAM5‐Chem‐MAM7‐MOSAIC: Global Atmospheric Distribution and Radiative Effects of Nitrate Aerosol journal April 2021
Evaluation of Biogenic Organic Aerosols in the Amazon Rainforest Using WRF‐Chem With MOSAIC journal December 2021
Molecular Characteristics of Atmospheric Organosulfates During Summer and Winter Seasons in Two Cities of Southern and Northern China journal November 2022
Urban pollution greatly enhances formation of natural aerosols over the Amazon rainforest journal March 2019
Development of a hydrophilic interaction liquid chromatography (HILIC) method for the chemical characterization of water-soluble isoprene epoxydiol (IEPOX)-derived secondary organic aerosol journal January 2018
Organosulfates in aerosols downwind of an urban region in central Amazon journal January 2018
Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology journal January 2013
Reactive intermediates revealed in secondary organic aerosol formation from isoprene journal December 2009
Effects of anthropogenic emissions on aerosol formation from isoprene and monoterpenes in the southeastern United States journal December 2014
Coexistence of three liquid phases in individual atmospheric aerosol particles journal April 2021
Estimating the Secondary Organic Aerosol Contribution to PM 2.5 Using the EC Tracer Method Special Issue of Aerosol Science and Technology on Findings from the Fine Particulate Matter Supersites Program journal December 2004
Effects of volatility, viscosity, and non-ideality on particle–particle mixing timescales of secondary organic aerosols journal September 2023
Modal Aerosol Dynamics Modeling journal January 1997
Within‐plant isoprene oxidation confirmed by direct emissions of oxidation products methyl vinyl ketone and methacrolein journal November 2011
Unexpected Epoxide Formation in the Gas-Phase Photooxidation of Isoprene journal August 2009
Reactive uptake of N 2 O 5 by atmospheric aerosol is dominated by interfacial processes journal February 2021
Secondary Organic Aerosol Formation from Isoprene: Selected Research, Historic Account and State of the Art journal June 2021
Kinetic regimes and limiting cases of gas uptake and heterogeneous reactions in atmospheric aerosols and clouds: a general classification scheme journal January 2013
Overview of the Focused Isoprene eXperiment at the California Institute of Technology (FIXCIT): mechanistic chamber studies on the oxidation of biogenic compounds journal January 2014
Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements journal January 2015
Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) journal January 2016
Constraining condensed-phase formation kinetics of secondary organic aerosol components from isoprene epoxydiols journal January 2016
Assessing the impact of anthropogenic pollution on isoprene-derived secondary organic aerosol formation in PM 2.5 collected from the Birmingham, Alabama, ground site during the 2013 Southern Oxidant and Aerosol Study journal January 2016
On the implications of aerosol liquid water and phase separation for organic aerosol mass journal January 2017
Aircraft-based observations of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX-SOA) in the tropical upper troposphere over the Amazon region journal January 2018
Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US journal January 2018
Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition journal January 2018
Chamber-based insights into the factors controlling epoxydiol (IEPOX) secondary organic aerosol (SOA) yield, composition, and volatility journal January 2019
Low-volatility compounds contribute significantly to isoprene secondary organic aerosol (SOA) under high-NOx conditions journal January 2019
The acidity of atmospheric particles and clouds journal January 2020
Predicting secondary organic aerosol phase state and viscosity and its effect on multiphase chemistry in a regional-scale air quality model journal January 2020
Mass accommodation and gas–particle partitioning in secondary organic aerosols: dependence on diffusivity, volatility, particle-phase reactions, and penetration depth journal January 2021
Observation-based constraints on modeled aerosol surface area: implications for heterogeneous chemistry journal December 2022
Impact of phase state and non-ideal mixing on equilibration timescales of secondary organic aerosol partitioning journal January 2023
Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature) journal January 2006
A single parameter representation of hygroscopic growth and cloud condensation nucleus activity journal January 2007
ISORROPIA II: a computationally efficient thermodynamic equilibrium model for K+–Ca2+–Mg2+–NH4+–Na+–SO42−–NO3–Cl–H2O aerosols journal January 2007
Isoprene photooxidation: new insights into the production of acids and organic nitrates journal January 2009
The formation, properties and impact of secondary organic aerosol: current and emerging issues journal January 2009
The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions journal January 2012