A5005326229- Atmospheric chemistry and aerosols
- Air Quality and Health Impacts
- Atmospheric Ozone and Climate
- Carcinogens and Genotoxicity Assessment
- Porphyrin and Phthalocyanine Chemistry
- Air Quality Monitoring and Forecasting
- Metal-Catalyzed Oxygenation Mechanisms
- DNA and Nucleic Acid Chemistry
- Toxic Organic Pollutants Impact
- Indoor Air Quality and Microbial Exposure
- Organic Chemistry Cycloaddition Reactions
- DNA Repair Mechanisms
- Atmospheric and Environmental Gas Dynamics
- Atmospheric aerosols and clouds
- Catalytic Processes in Materials Science
- Microbial bioremediation and biosurfactants
- Asymmetric Synthesis and Catalysis
- Free Radicals and Antioxidants
- Sulfur Compounds in Biology
- Chemical Reaction Mechanisms
- Porphyrin Metabolism and Disorders
- Inorganic and Organometallic Chemistry
- Odor and Emission Control Technologies
- Catalysis and Oxidation Reactions
- Photosynthetic Processes and Mechanisms
University of North Carolina at Chapel Hill
2016-2025
Communities In Schools of Orange County
2017-2018
National Institute of Environmental Health Sciences
1999-2009
National Institutes of Health
2006-2009
Virginia Commonwealth University
1993-2006
Institut de Science et d'Ingénierie Supramoléculaires
2006
Newcastle University
2004
RTI International
2003
University of Arizona
2000
University of New Mexico
1998
Isoprene epoxydiols (IEPOX), formed from the photooxidation of isoprene under low-NO(x) conditions, have recently been proposed as precursors secondary organic aerosol (SOA) on basis mass spectrometric evidence. In present study, IEPOX isomers were synthesized in high purity (>99%) to investigate their potential form SOA via reactive uptake a series controlled dark chamber studies followed by reaction product analyses. IEPOX-derived was substantially observed only presence acidic aerosols,...
Isoprene is a substantial contributor to the global secondary organic aerosol (SOA) burden, with implications for public health and climate system. The mechanism by which isoprene-derived SOA formed influence of environmental conditions, however, remain unclear. We present evidence from controlled smog chamber experiments field measurements that in presence high levels nitrogen oxides (NO x = NO + 2 ) typical urban atmospheres, 2-methyloxirane-2-carboxylic acid (methacrylic epoxide, MAE)...
Isoprene significantly contributes to organic aerosol in the southeastern United States where biogenic hydrocarbons mix with anthropogenic emissions. In this work, Community Multiscale Air Quality model is updated predict isoprene from epoxides produced under both high- and low-NOx conditions. The new aqueous pathways allow for explicit predictions of two key isoprene-derived species, 2-methyltetrols 2-methylglyceric acid, that are more consistent observations than estimates based on...
The reactive uptake of isoprene-derived epoxydiols (IEPOX) is thought to be a significant source atmospheric secondary organic aerosol (SOA). However, the IEPOX reaction probability (γIEPOX) and its dependence upon particle composition remain poorly constrained. We report measurements γIEPOX for trans-β-IEPOX, predominant isomer, on submicron particles as function composition, acidity, relative humidity (RH). Particle acidity had strongest effect. more than 500 times greater ammonium...
Abstract. A suite of offline and real-time gas- particle-phase measurements was deployed at Look Rock, Tennessee (TN), during the 2013 Southern Oxidant Aerosol Study (SOAS) to examine effects anthropogenic emissions on isoprene-derived secondary organic aerosol (SOA) formation. High- low-time-resolution PM2.5 samples were collected for analysis known tracer compounds in SOA by gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) ultra performance liquid chromatography/diode...
We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. results utilizing a Filter Inlet for Gases AEROsol coupled to chemical ionization mass spectrometer (CIMS). focus on volatility composition isoprene derived organic tracers bulk aerosol. By online molecular information provided by FIGAERO–CIMS, we show that vast majority commonly reported epoxydiol (IEPOX) secondary (SOA) is from...
Real-time continuous chemical measurements of fine aerosol were made using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) during summer and fall 2011 in downtown Atlanta, Georgia. Organic mass spectra measured by the ACSM analyzed positive matrix factorization (PMF), yielding three conventional factors: hydrocarbon-like organic (HOA), semivolatile oxygenated (SV-OOA), low-volatility (LV-OOA). An additional OOA factor that contributed to 33 ± 10% was resolved summer. This had a...
Acid-catalyzed reactions between gas- and particle-phase constituents are critical to atmospheric secondary organic aerosol (SOA) formation. The aerosol-phase state is thought influence the reactive uptake of gas-phase precursors particles by altering diffusion rates within particles. However, few experimental studies have explored precise role on processes. This laboratory study systematically examines coefficient (γ) trans-β-isoprene epoxydiol (trans-β-IEPOX), predominant IEPOX isomer,...
In the present study, formation of aromatic organosulfates (OSs) from photo-oxidation polycyclic hydrocarbons (PAHs) was investigated. Naphthalene (NAP) and 2-methylnaphthalene (2-MeNAP), two most abundant gas-phase PAHs thought to represent "missing" sources urban SOA, were photochemically oxidized in an outdoor smog chamber facility presence nonacidified acidified sulfate seed aerosol. Effects aerosol composition, acidity relative humidity on OS examined. Chemical characterization SOA...
Secondary organic aerosol (SOA) produced from reactive uptake and multiphase chemistry of isoprene epoxydiols (IEPOX) has been found to contribute substantially (upward 33%) the fine mass over Southeastern U.S. Brown carbon (BrC) in rural areas this region linked secondary sources summer when influence biomass burning is low. We demonstrate formation light-absorbing (290 < λ 700 nm) SOA constituents trans-β-IEPOX onto preexisting sulfate aerosols as a potential source BrC. IEPOX-derived BrC...
Acid-driven multiphase chemistry of isoprene epoxydiols (IEPOX), key oxidation products, with inorganic sulfate aerosol yields substantial amounts secondary organic (SOA) through the formation organosulfur compounds. The extent and implications inorganic-to-organic conversion, however, are unknown. In this article, we demonstrate that extensive consumption occurs, which increases IEPOX-to-inorganic concentration ratio (IEPOX/Sulfinorg), as determined by laboratory measurements....
Atmospheric oxidation of isoprene under low-NOx conditions leads to the formation hydroxyhydroperoxides (ISOPOOH). Subsequent ISOPOOH largely produces epoxydiols (IEPOX), which are known secondary organic aerosol (SOA) precursors. Although SOA from IEPOX has been previously examined, systematic studies characterization through a non-IEPOX route 1,2-ISOPOOH lacking. In present work, authentic was systematically examined with varying compositions and relative humidity. High yields highly...
Abstract. The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation α-pinene under conditions high nitric oxide (NO) concentrations with varying relative humidity (RH) acidity was investigated in the University North Carolina dual outdoor smog chamber facility. SOA enhanced to that OH-initiated presence initially high-NO conditions. However, no effect RH on mass evident. Ozone (O3)-initiated ammonium sulfate (AS) seed coated showed...
Exposure to formaldehyde results in the formation of DNA-protein cross-links (DPCs) as a primary genotoxic effect. Although DPCs are biologically important and eight amino acids have been reported form stable adducts with formaldehyde, structures these not yet elucidated. We characterized formaldehyde-induced Lys, Cys, His, Trp dG, dA, dC. dT formed no cross-links, nor did Arg, Gln, Tyr, or Asn. Reaction Lys dG gave highest yield cross-linked products, followed by reaction Cys dG. Yields...
Abstract. We report the formation of aliphatic organosulfates (OSs) in secondary organic aerosol (SOA) from photooxidation C10–C12 alkanes. The results complement those our laboratories reporting OSs and sulfonates gas-phase oxidation polycyclic aromatic hydrocarbons (PAHs). Both studies strongly support anthropogenic precursors, as hypothesized on basis recent field which were detected fine collected several major urban locations. In this study, dodecane, cyclodecane decalin, considered to...
2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation MBO was examined smog chambers under varied initial nitric oxide (NO) acidity levels. Results indicate measurable SOA from low-NO conditions. Moreover, increasing found to enhance SOA. Chemical characterization laboratory-generated...
In the southeastern US, substantial emissions of isoprene from deciduous trees undergo atmospheric oxidation to form secondary organic aerosol (SOA) that contributes fine particulate matter (PM2.5). Laboratory studies have revealed anthropogenic pollutants, such as sulfur dioxide (SO2), oxides nitrogen (NO x ), and acidity, can enhance SOA formation hydroxyl radical (OH)-initiated isoprene; however, mechanisms by which specific pollutants in ambient PM2.5 remain unclear. As one aspect an...
Isoprene-derived secondary organic aerosol (SOA) is mainly formed through acid-catalyzed reactive uptake of isoprene-derived epoxydiols (IEPOX) onto sulfate particles. The effect IEPOX-derived SOA on the physicochemical properties existing aerosols and resulting capacity for further formation remains unclear. This study systematically examined influences phase state, morphology, acidity pre-existing particles, as well their implications reactivity evolution these By combining thermodynamic...
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...
A combination of flow reactor studies and chamber modeling is used to constrain two uncertain parameters central the formation secondary organic aerosol (SOA) from isoprene-derived epoxides: (1) rate heterogeneous uptake epoxide particle phase (2) molar fraction reactively taken up that contributes SOA, SOA yield (ϕSOA). Flow measurements trans-β-isoprene epoxydiol (trans-β-IEPOX) methacrylic acid (MAE) reaction probability (γ) were performed on atomized aerosols with compositions similar...
Highly oxygenated multifunctional organic compounds (HOMs) originating from biogenic emissions constitute a widespread source of aerosols in the pristine atmosphere. However, molecular forms which HOMs are present condensed phase upon gas-particle partitioning remain unclear. In this study, we show that highly molecules contain multiple peroxide functionalities readily cationized by attachment Na+ during electrospray ionization operated positive ion mode. With method, first identification...
A developed non-thermal analytical method effectively resolves and quantifies major IEPOX-SOA components in PM<sub>2.5</sub>.