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1. Rapid Formation of Sulfate Aerosols through Aqueous Aerosol Oxidation by Isoprene Hydroxy Hydroperoxides (ISOPOOH)

   YUE ZHANG, Jin Yan ( January 2020 , 38th Annual Meeting American Association for Aerosol Research)

   Abstract Number: 530 Working Group: Aerosol Chemistry Abstract Isoprene is the most abundant non-methane volatile organic compound (VOC) emitted globally. Isomeric isoprene hydroxy hydroperoxides (ISOPOOH), key photooxidation products of isoprene, likely comprise the second most abundant class of peroxides in the atmosphere, following hydrogen peroxide. Studies have shown that hydrogen peroxide plays important roles in the formation of inorganic sulfates in cloud water mimics. However, the potential for ISOPOOH to play a role in sulfate formation in wet aerosol oxidation from reduced sulfur species (such as inorganic sulfite) is not well understood. This study systematically investigates the reaction kinetics andmore »products of ISOPOOH reacting with particle phase inorganic sulfite and discusses implications to the sulfate aerosol budget. In order to examine the reaction kinetics of ISOPOOH with aqueous sulfite, ammonium bisulfite particles were injected into the UNC indoor environmental chamber under dark conditions with 70% RH. After the inorganic sulfite concentrations stabilized, selected concentrations of gas-phase 1,2-ISOPOOH was injected into the chamber to initiate the multiphase reaction. The gas-phase ISOPOOH and particle-phase species were sampled with online instruments, including a chemical ionization mass spectrometer (CIMS), an aerosol chemical speciation monitor (ACSM), and a particle-into-liquid sampler (PILS), and also collected by Teflon filters for offline molecular-level analyses by an ultra-performance liquid chromatography coupled to an electrospray ionization high resolution quadrupole time-of-flight mass spectrometry (UPLC-ESI-HR-QTOFMS). Results show that a significant amount of inorganic sulfite was converted to inorganic sulfate and organosulfates in the particle phase at relatively fast reaction rates, altering the chemical and physical properties of the particles including phase state, pH, reactivity, and composition. Given the high abundance and water solubility of ISOPOOH in the ambient environment, the multiphase reactions examined in our study indicate significant impacts of ISOPOOH on the atmospheric lifecycle of sulfur and the physicochemical properties of ambient particles. Access: https://aaarabstracts.com/2020/viewabstract.php?pid=530« less
2. Rapid Formation of Sulfate Aerosols through Aqueous Aerosol Oxidation by Isoprene Hydroxy Hydroperoxides (ISOPOOH)

   Zhang, Yue ; Yan, Jin ; Chen, Yuzhi ; Armstrong, N. Casimir ; Zhang, Zhenfa ; Gold, Avram ; Turpin, Barbara ; Surratt, Jason ( October 2020 , 28th meeting AAAR)

   Isoprene is the most abundant non‐methane volatile organic compound (VOC) emitted globally. Isomeric isoprene hydroxy hydroperoxides (ISOPOOH), key photooxidation products of isoprene, likely comprise the second most abundant class of peroxides in the atmosphere, following hydrogen peroxide. Studies have shown that hydrogen peroxide plays important roles in the formation of inorganic sulfates in cloud water mimics. However, the potential for ISOPOOH to play a role in sulfate formation in wet aerosol oxidation from reduced sulfur species (such as inorganic sulfite) is not well understood. This study systematically investigates the reaction kinetics and products of ISOPOOH reacting with particle phase inorganicmore »sulfite and discusses implications to the sulfate aerosol budget. In order to examine the reaction kinetics of ISOPOOH with aqueous sulfite, ammonium bisulfite particles were injected into the UNC indoor environmental chamber under dark conditions with 70% RH. After the inorganic sulfite concentrations stabilized, selected concentrations of gas‐phase 1,2‐ISOPOOH was injected into the chamber to initiate the multiphase reaction. The gas‐phase ISOPOOH and particle‐phase species were sampled with online instruments, including a chemical ionization mass spectrometer (CIMS), an aerosol chemical speciation monitor (ACSM), and a particle‐into‐liquid sampler (PILS), and also collected by Teflon filters for offline molecularlevel analyses by an ultra‐performance liquid chromatography coupled to an electrospray ionization high resolution quadrupole time‐of‐flight mass spectrometry (UPLC‐ESI‐HR‐QTOFMS). Results show that a significant amount of inorganic sulfite was converted to inorganic sulfate and organosulfates in the particle phase at relatively fast reaction rates, altering the chemical and physical properties of the particles including phase state, pH, reactivity, and composition. Given the high abundance and water solubility of ISOPOOH in the ambient environment, the multiphase reactions examined in our study indicate significant impacts of ISOPOOH on the atmospheric lifecycle of sulfur and the physicochemical properties of ambient particles.« less
3. Rapid Formation of Sulfate Aerosols through Aqueous Aerosol Oxidation by Isoprene Hydroxy Hydroperoxides (ISOPOOH).

   Zang, Yue ; Yan, Jin ; Chen, Yuzhi ; Armstrong, Cazimir ; Zhang, Zhenfa ; Gold, Avram ; Turpin, Barbara ; Surratt, Jason ( October 2020 , 38th meeting American Association for Aerosol Research)

   Isoprene is the most abundant non‐methane volatile organic compound (VOC) emitted globally. Isomeric isoprene hydroxy hydroperoxides (ISOPOOH), key photooxidation products of isoprene, likely comprise the second most abundant class of peroxides in the atmosphere, following hydrogen peroxide. Studies have shown that hydrogen peroxide plays important roles in the formation of inorganic sulfates in cloud water mimics. However, the potential for ISOPOOH to play a role in sulfate formation in wet aerosol oxidation from reduced sulfur species (such as inorganic sulfite) is not well understood. This study systematically investigates the reaction kinetics and products of ISOPOOH reacting with particle phase inorganicmore »sulfite and discusses implications to the sulfate aerosol budget. In order to examine the reaction kinetics of ISOPOOH with aqueous sulfite, ammonium bisulfite particles were injected into the UNC indoor environmental chamber under dark conditions with 70% RH. After the inorganic sulfite concentrations stabilized, selected concentrations of gas‐phase 1,2‐ISOPOOH was injected into the chamber to initiate the multiphase reaction. The gas‐phase ISOPOOH and particle‐phase species were sampled with online instruments, including a chemical ionization mass spectrometer (CIMS), an aerosol chemical speciation monitor (ACSM), and a particle‐into‐liquid sampler (PILS), and also collected by Teflon filters for offline molecular level analyses by an ultra‐performance liquid chromatography coupled to an electrospray ionization high resolution quadrupole time‐of‐flight mass spectrometry (UPLC‐ESI‐HR‐QTOFMS). Results show that a significant amount of inorganic sulfite was converted to inorganic sulfate and organosulfates in the particle phase at relatively fast reaction rates, altering the chemical and physical properties of the particles including phase state, pH, reactivity, and composition. Given the high abundance and water solubility of ISOPOOH in the ambient environment, the multiphase reactions examined in our study indicate significant impacts of ISOPOOH on the atmospheric lifecycle of sulfur and the physicochemical properties of ambient particles.« less
4. Kinetics and Products of Heterogeneous Hydroxyl Radical Oxidation of Isoprene Epoxydiol‐Derived SOA.

   Yan, Jin ; Zhang, Yue ; Chen, Yuzhi ; Armstrong, Cazimir ; Zhang, Zhenfa ; Gold, Avram ; Lambe, Andrew ; Turpin, Barbara ; Ault, Andrew ( October 2021 , 2021 AAAR 39th Annual Conference)

   In isoprene‐rich regions, acid‐catalyzed multiphase reactions of isoprene epoxydiols (IEPOX) with inorganic sulfate (Sulfinorg) particles form secondary organic aerosol (IEPOX‐SOA), extensively converting Sulfinorg to lowervolatility particulate organosulfates (OSs), including 2‐ methyltetrol sulfates (2‐MTSs) and their dimers. Recently, we showed that heterogeneous hydroxyl radical (OH) oxidation of particulate 2‐MTSs generated multifunctional OS products. However, atmospheric models assume that OS‐rich IEPOX‐SOA particles remain unreactive towards heterogeneous OH oxidation, and limited laboratory studies have been conducted to examine the heterogeneous OH oxidation kinetics of full IEPOX‐SOA mixtures. Hence, this study investigated the kinetics and products resulting from heterogeneous OH oxidation of freshly‐generated IEPOXSOAmore »in order to help derive model‐ready parameterizations. First, gas‐phase IEPOX was reacted with acidic Sulfinorg particles under dark conditions in order to form fresh IEPOX‐SOA particles. These particles were then subsequently aged at RH of 56% in an oxidation flow reactor at OH exposures ranging from 0~15 days of equivalent atmospheric exposure. Aged IEPOX‐SOA particles were sampled by an online aerosol chemical speciation monitor (ACSM) and collected onto Teflon filters for off‐line molecular‐level chemical analyses by hydrophilic liquid interaction chromatography method interfaced to electrospray ionization high‐resolution quadrupole time‐offlight mass spectrometry (HILIC/ESI‐HR‐QTOFMS). Our results show that heterogeneous OH oxidation only caused a 7% decay of IEPOX‐SOA by 10 days exposure, likely owing to the inhibition of reactive uptake of OH as fresh IEPOXSOA particles have an inorganic core‐organic shell morphology. A significantly higher fraction of IEPOX‐SOA (~37%) decayed by 15 days exposure, likely due to the increasing reactive uptake of OH as IEPOX‐SOA become more liquid‐like with aging. Freshly‐generated IEPOX‐SOA constituents exhibited varying degrees of aging with 2‐MTSdimers being the most reactive, followed by 2‐MTSs and 2‐ methyltetrols (2‐MTs), respectively. Notably, extensive amounts of previously characterized particle‐phase products in ambient fine aerosols were detected in our laboratory‐aged IEPOX‐SOA samples.« less
5. Modelling the gas–particle partitioning and water uptake of isoprene-derived secondary organic aerosol at high and low relative humidity

   https://doi.org/10.5194/acp-22-215-2022  

   Amaladhasan, Dalrin Ampritta ; Heyn, Claudia ; Hoyle, Christopher R. ; El Haddad, Imad ; Elser, Miriam ; Pieber, Simone M. ; Slowik, Jay G. ; Amorim, Antonio ; Duplissy, Jonathan ; Ehrhart, Sebastian ; et al ( January 2022 , Atmospheric Chemistry and Physics)

   Abstract. This study presents a characterization of the hygroscopic growth behaviour and effects of different inorganic seed particles on the formation of secondary organic aerosols (SOAs) from the dark ozone-initiated oxidation of isoprene at low NOx conditions. We performed simulations of isoprene oxidation using a gas-phase chemical reaction mechanism based onthe Master Chemical Mechanism (MCM) in combination with an equilibriumgas–particle partitioning model to predict the SOA concentration. Theequilibrium model accounts for non-ideal mixing in liquid phases, includingliquid–liquid phase separation (LLPS), and is based on the AIOMFAC (Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients) model for mixture non-ideality and the EVAPORATIONmore »(Estimation of VApour Pressure of ORganics, Accounting for Temperature,Intramolecular, and Non-additivity effects) model for pure compound vapourpressures. Measurements from the Cosmics Leaving Outdoor Droplets (CLOUD)chamber experiments, conducted at the European Organization for NuclearResearch (CERN) for isoprene ozonolysis cases, were used to aid inparameterizing the SOA yields at different atmospherically relevanttemperatures, relative humidity (RH), and reacted isoprene concentrations. To represent the isoprene-ozonolysis-derived SOA, a selection of organicsurrogate species is introduced in the coupled modelling system. The modelpredicts a single, homogeneously mixed particle phase at all relativehumidity levels for SOA formation in the absence of any inorganic seedparticles. In the presence of aqueous sulfuric acid or ammonium bisulfateseed particles, the model predicts LLPS to occur below ∼ 80 % RH, where the particles consist of an inorganic-rich liquid phase andan organic-rich liquid phase; however, this includes significant amounts of bisulfate and water partitioned to the organic-rich phase. The measurements show an enhancement in the SOA amounts at 85 % RH, compared to 35 % RH, for both the seed-free and seeded cases. The model predictions of RH-dependent SOA yield enhancements at 85 % RH vs. 35 % RH are 1.80 for a seed-free case, 1.52 for the case with ammonium bisulfate seed, and 1.06 for the case with sulfuric acid seed. Predicted SOA yields are enhanced in the presence of an aqueous inorganic seed, regardless of the seed type (ammonium sulfate, ammonium bisulfate, or sulfuric acid) in comparison with seed-free conditions at the same RH level. We discuss the comparison of model-predicted SOA yields with a selection of other laboratory studies on isoprene SOA formation conducted at different temperatures and for a variety of reacted isoprene concentrations. Those studies were conducted at RH levels at or below 40 % with reported SOA mass yields ranging from 0.3 % up to 9.0 %, indicating considerable variations. A robust feature of our associated gas–particle partitioning calculations covering the whole RH range is the predicted enhancement of SOA yield at high RH (> 80 %) compared to low RH (dry) conditions, which is explained by the effect of particle water uptake and its impact on the equilibrium partitioning of all components.« less