A5027064973- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Atmospheric aerosols and clouds
- Advanced Chemical Sensor Technologies
- Spectroscopy and Laser Applications
- Atmospheric and Environmental Gas Dynamics
- Water Quality Monitoring and Analysis
- COVID-19 impact on air quality
- Catalytic Processes in Materials Science
- Vehicle emissions and performance
- Analytical Chemistry and Sensors
- Chemical Synthesis and Reactions
- Odor and Emission Control Technologies
- Atomic and Subatomic Physics Research
- Chemical Thermodynamics and Molecular Structure
- Inorganic and Organometallic Chemistry
- Oxidative Organic Chemistry Reactions
- Analytical Chemistry and Chromatography
- Mass Spectrometry Techniques and Applications
- Infection Control and Ventilation
- Plant responses to elevated CO2
Georgia Institute of Technology
2019-2025
Rutgers, The State University of New Jersey
2024
Harvard University
2016-2023
University of Wisconsin–Madison
2014-2016
Madison Group (United States)
2016
Gas-phase low volatility organic compounds (LVOC), produced from oxidation of isoprene 4-hydroxy-3-hydroperoxide (4,3-ISOPOOH) under low-NO conditions, were observed during the FIXCIT chamber study. Decreases in LVOC directly correspond to appearance and growth secondary aerosol (SOA) consistent elemental composition, indicating that condense (at OA below 1 μg m–3). This represents first simultaneous measurement condensing species both gas particle phases. The SOA formation this study is...
We use a large laboratory, modeling, and field dataset to investigate the isoprene + O<sub>3</sub> reaction, with goal of better understanding fates C<sub>1</sub> C<sub>4</sub> Criegee intermediates in atmosphere.
The nitrate radical (NO3) oxidation of isoprene is an important contributor to secondary organic aerosol (SOA). Isoprene has two double bonds which allow for multigeneration occur. effects chemistry on the gas- and particle-phase product distributions + NO3 system are not fully understood. In this study, we conduct chamber experiments by varying ratio N2O5 (precursor NO3) concentration from 1:1 14:1 investigate formation products in both phases under different levels. Multigeneration leads...
The atmospheric oxidation of isoprene by the OH radical leads to formation several isomers an unsaturated hydroxy hydroperoxide, ISOPOOH. Oxidation ISOPOOH produces epoxydiols, IEPOX, which have been shown contribute mass secondary organic aerosol (SOA). We present kinetic rate constant measurements for + using synthetic standards two major isomers: (1,2)- and (4,3)-ISOPOOH. At 297 K, total is 7.5 ± 1.2 × 10(-11) cm(3) molecule(-1) s(-1) (1,2)-ISOPOOH 1.18 0.19 10(-10) Abstraction...
Abstract Atmospheric volatile organic compound (VOC) oxidation mechanisms under pristine (rural/remote) and urban (anthropogenically‐influenced) conditions follow distinct pathways due to large differences in nitrogen oxide (NO x ) concentrations. These two lead products that have different chemical physical properties reactivity. Under conditions, isoprene hydroxy hydroperoxides (ISOPOOHs) are the dominant first‐generation products. Utilizing authentic ISOPOOH standards, we demonstrate of...
With a large global emission rate and high reactivity, isoprene has profound effect upon atmospheric chemistry composition. The pathways by which converts to secondary organic aerosol (SOA) how anthropogenic pollutants such as nitrogen oxides sulfur affect this process are subjects of intense research because particles Earth's climate local air quality. In the absence both reactive aqueous seed particles, we measure SOA mass yields from photochemical oxidation up 15%, factors 2 or more...
Significance For isolated regions of the planet, organic peroxy radicals produced as intermediates atmospheric photochemistry have been expected to follow HO 2 rather than NO pathways. Observational evidence, however, has lacking. An accurate understanding relative roles two pathways is needed for quantitative predictions concentrations particulate matter, oxidation capacity, and consequent environmental climate impacts. The results herein, based on measurements, find that ratio reaction...
Abstract. We present measurements of secondary organic aerosol (SOA) formation from isoprene photochemical oxidation in an environmental simulation chamber at a variety oxidant conditions and using dry neutral seed particles to suppress acid-catalyzed multiphase chemistry. A high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) utilizing iodide-adduct coupled the Filter Inlet for Gases Aerosols (FIGAERO) allowed simultaneous online sampling gas particle...
The oxidation of sulfur dioxide (SO2) by peroxides leads to the formation sulfate in cloudwater, contributing particulate matter (PM) formation. reaction with hydrogen peroxide (H2O2) is considered be main cloud pathway. Previous studies have examined SO2 cloudwater small organic one functional group; however, multifunctional hydroperoxides, which are expected higher water solubility and reactivity, has not been examined. We investigate aqueous two isomers isoprene hydroxyl hydroperoxide...
Abstract. Molecules with hydroperoxide functional groups are of extreme importance to both the atmospheric and biological chemistry fields. In this work, an analytical method is presented for identification organic hydroperoxides peroxy acids (ROOH) by direct infusion liquid samples into a positive-ion pressure chemical ionization–tandem mass spectrometer ((+)-APCI-MS/MS). Under collisional dissociation conditions, characteristic neutral loss 51 Da (arising from H2O2+NH3) ammonium adducts...
A significant amount of furan species is emitted from biomass burning. They are highly reactive to hydroxyl (OH) and nitrate radicals (NO3), which can lead the formation secondary organic aerosol (SOA). Here, we investigate gas-phase oxidation SOA 3-methylfuran (C5H6O) via NO3 reaction. Experiments performed under dry conditions (RH < 5%) with different initial concentrations (from 95.9 562.8 ppb). We demonstrate that this reaction leads formation, yield ranging 1.6 2.4% for mass loading 5.1...
Hydroxymethyl hydroperoxide (HMHP), formed in the reaction of C1 Criegee intermediate with water, is among most abundant organic peroxides atmosphere. Although OH thought to represent one important atmospheric removal processes for HMHP, this has been largely unstudied laboratory. Here, we present measurements kinetics and products HMHP OH. was oxidized by an environmental chamber; decay formation formic acid formaldehyde were monitored over time using CF3O- chemical ionization mass...
Isoprene hydroxy hydroperoxides (ISOPOOH) formed by the photooxidation of isoprene under low-NO conditions play an important role in formation and evolution secondary organic aerosols, yet multiphase processes ISOPOOH are poorly understood. By applying electron paramagnetic resonance spectroscopy, we observe that undergoes aqueous-phase decomposition upon interacting with Fe(II) ions to form OH radicals at room temperature. To reproduce measured dependence on Fe concentrations kinetic...
The family of atmospheric oxides nitrogen, NOy (e.g., nitrogen (NOx) + nitric acid (HNO3) nitrous (HONO) peroxyacetyl nitrate (PAN) particulate (pNO3-) other), have an influential role in chemistry, climate, and the environment. (δ15N) oxygen (δ18O Δ17O) stable isotopes are novel tools for potentially tracking emission sources quantifying oxidation chemistry. However, there is a lack well-established methods, particularly speciated gas-phase components NOy, to accurately quantify δ15N, δ18O,...
Abstract. The hydroxyl (OH), hydroperoxy (HO2), and organic peroxy (RO2) radicals play important roles in atmospheric chemistry. In the presence of nitrogen oxides (NOx), reactions between OH volatile compounds (VOCs) can initiate a radical propagation cycle that leads to production ozone secondary aerosols. Previous measurements these under low-NOx conditions forested environments characterized by emissions biogenic VOCs, including isoprene monoterpenes, have shown discrepancies with...
Abstract. In-cloud chemistry has important ramifications for atmospheric particulate matter formation and gas-phase chemistry. Recent work shown that, like hydrogen peroxide (H2O2), the two main isomers of isoprene hydroxyl hydroperoxide (ISOPOOH) oxidize sulfur dioxide dissolved in cloud droplets (SO2,aq) to sulfate. The revealed that pathway SO2,aq oxidation with ISOPOOH differs from H2O2. We investigate chemical mechanisms cloud-relevant pH range 3–6 compare them previously reported H2O2,...
The COVID-19 pandemic increased the demand for indoor air cleaners. While some commercial electronic cleaners can be effective in reducing primary pollutants and inactivating bioaerosol, studies on formation of secondary products from oxidation chemistry during their use are limited. Here, we measured oxygenated volatile organic compounds (OVOCs) chemical composition particles generated a hydroxyl radical generator an office. During operation, enhancements OVOCs, especially...
Advances in low-cost sensors (LCS) for monitoring air quality have opened new opportunities to characterize finer spatial and temporal resolutions. In this study, we deployed LCS that measure both gas (CO, NO, NO2, O3) particle concentrations co-located research-grade instruments Atlanta, GA, investigate the capability of resolving pollutant sources using non-negative matrix factorization (NMF) a moderately polluted urban area. We provide comparison applying NMF technique normalized...
Multifunctional organic nitrates derived from biogenic volatile compounds are important for understanding ozone and secondary aerosol production oxidation reactions in the presence of nitrogen oxides. Their measurement is challenging, part because quantification these difficult time consuming due to techniques required synthesize purify authentic standards. We describe a novel online synthesis separation technique demonstrate its use calibration chemical ionization mass spectrometer using...
Recent laboratory experiments have shown that a first generation isoprene oxidation product, ISOPOOH, can decompose to methyl vinyl ketone (MVK) and methacrolein (MACR) on instrument surfaces, leading overestimates of MVK MACR concentrations. Formaldehyde (HCHO) was suggested as decomposition co-product, raising concern in situ HCHO measurements may also be affected by an ISOPOOH interference. The measurement artifact from for the NASA In Situ Airborne (ISAF) investigated two major isomers,...
Air quality in indoor environments can have significant impacts on people's health, comfort, and productivity. Particulate matter (PM; also referred to as aerosols) is an important type of air pollutant, exposure outdoor PM has been associated with a variety diseases. In addition, there increasing recognition concern airborne transmission viruses, including severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2), especially environments. Despite its importance, data during the COVID-19...
Abstract. We present measurements of secondary organic aerosol (SOA) formation from isoprene photochemical oxidation formed in an environmental simulation chamber using dry neutral seed particles, thereby suppressing the role acid catalyzed multiphase chemistry, at a variety oxidant conditions. A high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) utilizing iodide-adduct coupled to Filter Inlet for Gases and AEROsols (FIGAERO) allowed simultaneous online...
Abstract. Recent laboratory experiments have shown that a first generation isoprene oxidation product, ISOPOOH, can decompose to methyl vinyl ketone (MVK) and methacrolein (MACR) on instrument surfaces, leading overestimates of MVK MACR concentrations. Formaldehyde (HCHO) was suggested as decomposition co-product, raising concern in situ HCHO measurements may also be affected by an ISOPOOH interference. The measurement artifact from for the NASA In Situ Airborne (ISAF) investigated two major...