A5035496453- Atmospheric chemistry and aerosols
- Air Quality and Health Impacts
- Atmospheric aerosols and clouds
- Air Quality Monitoring and Forecasting
- Fire effects on ecosystems
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Vehicle emissions and performance
- Advanced Chemical Sensor Technologies
- Catalytic Processes in Materials Science
- Aeolian processes and effects
- Odor and Emission Control Technologies
- Mass Spectrometry Techniques and Applications
- Fire dynamics and safety research
- Water Quality Monitoring and Analysis
- Toxic Organic Pollutants Impact
- Thermochemical Biomass Conversion Processes
- Indoor Air Quality and Microbial Exposure
- Analytical Chemistry and Chromatography
- Catalysis and Oxidation Reactions
- Spectroscopy and Laser Applications
- Isotope Analysis in Ecology
- Chemistry and Chemical Engineering
- Advanced Aircraft Design and Technologies
- Wind and Air Flow Studies
National Oceanic and Atmospheric Administration
2016-2025
Cooperative Institute for Research in Environmental Sciences
2016-2025
NOAA Chemical Sciences Laboratory
2020-2025
University of Colorado Boulder
2016-2025
NOAA Earth System Research Laboratory
2016-2020
California Institute of Technology
2011-2017
Pasadena City College
2016
University of Arizona
2015
Abstract. Volatile and intermediate-volatility non-methane organic gases (NMOGs) released from biomass burning were measured during laboratory-simulated wildfires by proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF). We identified NMOG contributors to more than 150 PTR ion masses using gas chromatography (GC) pre-separation with electron ionization, H3O+ chemical NO+ an extensive literature review, time series correlation, providing higher certainty for identifications has...
Significance Recent work in Los Angeles has shown that urban volatile organic compound (VOC) emissions from consumer and industrial products—termed chemical products (VCPs)—are now an important source of ozone precursors. Using advancements VOC instrumentation, we show VCP are ubiquitous regions can be identified via unique fingerprints. Through detailed modeling, VCPs as to production fossil fuel VOCs the chemistry have significant impacts on model simulations key atmospheric processes....
Abstract. The formation of secondary organic aerosol from oxidation phenol, guaiacol (2-methoxyphenol), and syringol (2,6-dimethoxyphenol), major components biomass burning, is described. Photooxidation experiments were conducted in the Caltech laboratory chambers under low-NOx (< 10 ppb) conditions using H2O2 as OH source. Secondary (SOA) yields (ratio mass SOA formed to primary reacted) greater than 25% are observed. Aerosol growth rapid linear with conversion, consistent essentially...
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...
Abstract. The reactive partitioning of cis and trans β-IEPOX was investigated on hydrated inorganic seed particles, without the addition acids. No organic aerosol (OA) formation observed dry ammonium sulfate (AS); however, prompt efficient OA growth for AS seeds at liquid water contents 40–75% total particle mass. from IEPOX is a kinetically limited process, thus continues if there reservoir gas-phase IEPOX. There appears to be no differences, within error, in or composition attributable /...
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.
Despite decades of declining air pollution, urban U.S. areas are still affected by summertime ozone and wintertime particulate matter exceedance events. Volatile organic compounds (VOCs) known precursors secondary aerosol (SOA) photochemically produced ozone. Urban VOC emission sources, including on-road transportation emissions, have decreased significantly over the past few through successful regulatory measures. These drastic reductions in emissions led to a change distribution...
With traffic emissions of volatile organic compounds (VOCs) decreasing rapidly over the last decades, contributions from other source categories, such as chemical products (VCPs), have become more apparent in urban air. In this work, situ measurements various VOCs are reported for New York City, Pittsburgh, Chicago, and Denver. The magnitude different emission sources relative to is determined by measuring enhancement individual benzene, a known tracer fossil fuel United States. ratios...
Abstract. Biomass burning is a large source of volatile organic compounds (VOCs) and many other trace species to the atmosphere, which can act as precursors secondary pollutants such ozone fine particles. Measurements performed with proton-transfer-reaction time-of-flight mass spectrometer during FIREX 2016 laboratory intensive were analyzed positive matrix factorization (PMF), in order understand instantaneous variability VOC emissions from biomass burning, simplify description these types...
Abstract. Chamber oxidation experiments conducted at the Fire Sciences Laboratory in 2016 are evaluated to identify important chemical processes contributing hydroxy radical (OH) chemistry of biomass burning non-methane organic gases (NMOGs). Based on decay primary carbon measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS), it is confirmed that furans and oxygenated aromatics among NMOGs emitted from western United States fuel types with highest reactivities...
Biomass burning is the largest combustion-related source of volatile organic compounds (VOCs) to atmosphere. We describe development a state-of-the-science model simulate photochemical formation secondary aerosol (SOA) from biomass-burning emissions observed in dry (RH <20%) environmental chamber experiments. The modeling supported by (i) new oxidation measurements, (ii) detailed concurrent measurements SOA precursors emissions, and (iii) parameters for heterocyclic oxygenated aromatic based...
Wildfires are a substantial but poorly quantified source of tropospheric ozone (O3). Here, to investigate the highly variable O3 chemistry in wildfire plumes, we exploit situ chemical characterization western wildfires during FIREX-AQ flight campaign and show that production can be predicted as function experimentally constrained OH exposure, volatile organic compound (VOC) reactivity, fate peroxy radicals. The exhibits rapid transition regimes. Within few daylight hours, formation...
Abstract. Anthropogenic secondary organic aerosol (ASOA), formed from anthropogenic emissions of compounds, constitutes a substantial fraction the mass submicron in populated areas around world and contributes to poor air quality premature mortality. However, precursor sources ASOA are poorly understood, there large uncertainties health benefits that might accrue reducing emissions. We show production 11 urban on three continents is strongly correlated with reactivity specific volatile...
Abstract The NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) experiment was a multi‐agency, inter‐disciplinary research effort to: (a) obtain detailed measurements of trace gas aerosol emissions from wildfires prescribed fires using aircraft, satellites ground‐based instruments, (b) make extensive suborbital remote sensing fire dynamics, (c) assess local, regional, global modeling fires, (d) strengthen connections observables the ground such as fuels...
Abstract. Proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a technique commonly used to measure ambient volatile organic compounds (VOCs) in urban, rural, and remote environments. PTR-ToF-MS known produce artifacts from ion fragmentation, which complicates the interpretation quantification of key atmospheric VOCs. This study evaluates extent fragmentation other ionization processes impact urban measurements ions typically assigned isoprene (m/z 69, C5H8H+),...
Abstract. Extensive airborne measurements of non-methane organic gases (NMOGs), methane, nitrogen oxides, reduced species, and aerosol emissions from US wild prescribed fires were conducted during the 2019 NOAA/NASA Fire Influence on Regional to Global Environments Air Quality campaign (FIREX-AQ). Here, we report atmospheric enhancement ratios (ERs) inferred emission factors (EFs) for compounds measured board NASA DC-8 research aircraft nine wildfires one fire, which encompass a range...
Abstract. Hydroxyl radical (OH) oxidation of toluene produces ring-retaining products: cresol and benzaldehyde, ring-opening bicyclic intermediate compounds epoxides. Here, first- later-generation OH products from benzaldehyde are identified in laboratory chamber experiments. For first-generation identified, but not detected. cresol, low-volatility (saturation mass concentration, C* ∼ 3.5 × 104 − 7.7 10−3 µg m−3), identified. Subsequent addition to the aromatic ring o-cresol leads such as...
Decamethylcyclopentasiloxane (D5) is a cyclic volatile methyl siloxane (cVMS) that widely used in consumer products and commonly observed urban air. This study quantifies the ambient mixing ratios of D5 from ground sites two North American cities (Boulder, CO, USA, Toronto, ON, CA). From these data, we estimate diurnal emission profile Boulder, CO. Ambient were consistent with those measured at other locations; however, pattern exhibited similarities traffic-related compounds such as...
Abstract. Teflon chambers are ubiquitous in studies of atmospheric chemistry. Secondary organic aerosol (SOA) formation can be underestimated, owing to deposition SOA-forming vapors the chamber wall. We present here an experimental protocol and a model framework constrain vapor–wall interactions chambers. measured wall rates 25 oxidized compounds generated from photooxidation isoprene, toluene, α-pinene, dodecane two that had been extensively used new unused found extent prior use did not...
Biomass burning (BB) is a large source of reactive compounds in the atmosphere. While daytime photochemistry BB emissions has been studied some detail, there little focus on nighttime reactions despite potential for substantial oxidative and heterogeneous chemistry. Here, we present first analysis aircraft intercepts agricultural plumes using observations from NOAA WP-3D during 2013 Southeast Nexus (SENEX) campaign. We use these conjunction with detailed chemical box modeling to investigate...
Abstract. Secondary organic aerosol (SOA) yields were measured for cyclododecane, hexylcyclohexane, n-dodecane, and 2-methylundecane under high-NOx conditions, in which alkyl proxy radicals (RO2) react primarily with NO, low-NOx RO2 reacts HO2. Experiments run until 95–100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases using a new approach that requires only suspended particle number-size distribution data accounts size-dependent losses...
We describe the products of reaction hydroperoxy radical (HO(2)) with alkylperoxy formed following addition nitrate (NO(3)) and O(2) to isoprene. NO(3) adds preferentially C(1) position isoprene (>6 times more favorably than C(4)), followed by produce a suite nitrooxy radicals (RO(2)). At an RO(2) lifetime ∼30 s, δ-nitrooxy β-nitrooxy are present in similar amounts. Gas-phase product yields from + HO(2) pathway identified as 0.75-0.78 hydroperoxide (INP), 0.22 methyl vinyl ketone (MVK)...
Abstract Volatile organic compounds (VOCs) emitted from residential wood and crop residue burning were measured in Colorado, U.S. When compared to the emissions burning, exhibited markedly lower concentrations of acetonitrile, a commonly used biomass tracer. For both herbaceous arboraceous fuels, nitrogen‐containing VOCs (NVOCs) strongly depend on fuel nitrogen content; therefore, low NVOC result combustion low‐nitrogen fuel. Consequently, hazardous human health, such as HNCO HCN, formation...