A5025491485- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Atmospheric aerosols and clouds
- Air Quality and Health Impacts
- Atmospheric and Environmental Gas Dynamics
- Air Quality Monitoring and Forecasting
- Fire effects on ecosystems
- Vehicle emissions and performance
- Odor and Emission Control Technologies
- Toxic Organic Pollutants Impact
- Spectroscopy and Laser Applications
- Advanced Aircraft Design and Technologies
- Aeolian processes and effects
- Catalytic Processes in Materials Science
- Cyclone Separators and Fluid Dynamics
- Analytical Chemistry and Chromatography
- Groundwater and Isotope Geochemistry
- Water Quality Monitoring and Analysis
- Mass Spectrometry Techniques and Applications
- Geography and Environmental Studies
- Marine and coastal ecosystems
- Industrial Gas Emission Control
- Nuclear Physics and Applications
- Geophysics and Gravity Measurements
- Mercury impact and mitigation studies
Cooperative Institute for Research in Environmental Sciences
2016-2025
University of Colorado Boulder
2016-2025
University of Colorado System
2014-2025
California Institute of Technology
2021
ORCID
2021
NSF National Center for Atmospheric Research
2020
Harvard University
2018
Aerodyne Research
2013
Helsinki Institute of Physics
2013
University of Helsinki
2013
Abstract Particulate brown carbon (BrC) in the atmosphere absorbs light at subvisible wavelengths and has poorly constrained but potentially large climate forcing impacts. BrC from biomass burning virtually unknown lifecycle atmospheric stability. Here, emitted intense wildfires was measured plumes transported over 2 days two main fires, during 2013 NASA SEAC4RS mission. Concurrent measurements of organic aerosol (OA) black (BC) mass concentration, BC coating thickness, absorption Ångström...
Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part the Southern Oxidant Aerosol Study. A large fraction pONs is highly functionalized, possessing between six eight oxygen atoms within each carbon number group, not common first generation alkyl previously reported. Using calibrations for isoprene hydroxynitrates measured molecular compositions, we estimate that account 3% 8% total...
Significance Atmospheric fine organic aerosol impacts air quality, climate, and human health. Speciating quantifying the sources of on molecular level improves understanding their formation chemistry hence resulting impacts. Such study, however, has not been possible due to chemical complexity atmospheric aerosol. Here, we provide comprehensive characterization samples from southeastern United States by combining state-of-the-art high-resolution mass spectrometry techniques. We find that...
Abstract. Isoprene emitted by vegetation is an important precursor of secondary organic aerosol (SOA), but the mechanism and yields are uncertain. Aerosol prevailingly aqueous under humid conditions typical isoprene-emitting regions. Here we develop aqueous-phase for isoprene SOA formation coupled to a detailed gas-phase oxidation scheme. The based on reactive uptake coefficients (γ) water-soluble products, including sensitivity acidity nucleophile concentrations. We apply this simulation...
Dimethyl sulfide (DMS), emitted from the oceans, is most abundant biological source of sulfur to marine atmosphere. Atmospheric DMS oxidized condensable products that form secondary aerosols affect Earth's radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report atmospheric discovery a previously unquantified oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations demonstrate it be...
Abstract Wildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured aircraft during Studies Emissions and Atmospheric Composition, Clouds Climate Coupling by Regional Surveys (SEAC 4 RS) Biomass Burning Observation Project (BBOP), both summer 2013. This study reports an extensive set emission factors (EFs) for over 80 gases 5 components submicron particulate matter (PM 1 ) these temperate wildfires. These include...
Abstract. We use an ensemble of surface (EPA CSN, IMPROVE, SEARCH, AERONET), aircraft (SEAC4RS), and satellite (MODIS, MISR) observations over the southeast US during summer–fall 2013 to better understand aerosol sources in region relationship between particulate matter (PM) optical depth (AOD). The GEOS-Chem global chemical transport model (CTM) with 25 × km2 resolution North America is used as a common platform interpret measurements different variables made at times locations. Sulfate...
Particle pH is a critical but poorly constrained quantity that affects many aerosol processes and properties, including composition, concentrations, toxicity. We assess PM1 as function of geographical location altitude, focusing on the northeastern U.S., based aircraft measurements from Wintertime Investigation Transport, Emissions, Reactivity campaign (1 February to 15 March 2015). water were predicted with ISORROPIA-II thermodynamic model validated by comparing observed partitioning...
Abstract. Formation of organic nitrates (RONO2) during oxidation biogenic volatile compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry RONO2 formation and degradation remains uncertain. Here we implement new BVOC mechanism (including updated isoprene chemistry, monoterpene particle uptake RONO2) in GEOS-Chem global chemical transport model with ∼ 25 × km2 resolution over North America. We evaluate using...
Abstract The Community Earth System Model version 2 (CESM2) includes three main atmospheric configurations: the Atmosphere 6 (CAM6) with simplified chemistry and a organic aerosol (OA) scheme, CAM6 comprehensive tropospheric stratospheric representation (CAM6‐chem), Whole Climate (WACCM6). Both, CAM6‐chem WACCM6 include more secondary aerosols (SOA) approach using Volatility Basis Set (VBS) scheme prognostic aerosols. This paper describes different OA schemes available in configurations of...
Abstract The Deep Convective Clouds and Chemistry (DC3) field experiment produced an exceptional dataset on thunderstorms, including their dynamical, physical, electrical structures impact the chemical composition of troposphere. gathered detailed information inflow outflow regions midlatitude thunderstorms in northeast Colorado, west Texas to central Oklahoma, northern Alabama. A unique aspect DC3 strategy was locate sample convective a day after active convection order measure...
Abstract. Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products mainly under low-NO conditions. Total IEPOX-SOA, may include SOA other parallel pathways, was quantified by applying positive matrix factorization (PMF) to mass spectrometer (AMS) measurements. The IEPOX-SOA fractions (OA) in multiple field studies across several continents summarized here and show consistent patterns with the concentration gas-phase...
We present results from a high-resolution chemical ionization time-of-flight mass spectrometer (HRToF-CIMS), operated with two different thermal desorption inlets, designed to characterize the gas and aerosol composition. Data field campaigns at forested sites are shown. Particle volatility distributions estimated using three methods: thermograms, elemental formulas, measured partitioning. Thermogram-based consistent those an (AMS) denuder, implying that is reproducible across very...
Abstract. At the Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS) field campaign in Colorado front range, July–August 2011, measurements of gas- and aerosol-phase organic nitrates enabled a study role NOx (NOx = NO + NO2) oxidation forest-emitted volatile compounds (VOCs) subsequent aerosol formation. Substantial formation peroxy- alkyl-nitrates is observed every morning, with an apparent 2.9% yield alkyl from daytime RO2 reactions. Aerosol-phase nitrates, however, peak concentration...
Significance Exposure to fine particulate matter is a leading cause of premature deaths and illnesses globally. In the eastern United States, substantial cuts in sulfur dioxide nitrogen oxides emissions have considerably lowered sulfate nitrate concentrations for all seasons except winter. Simulations that reproduce detailed airborne observations wintertime atmospheric chemistry over States indicate formation limited by availability oxidants acidity particles, respectively. These limitations...
Abstract. Organic aerosols (OA) that strongly absorb solar radiation in the near-UV are referred to as brown carbon (BrC). The sources, evolution, and optical properties of BrC remain highly uncertain contribute significantly uncertainty estimate global direct radiative effect (DRE) aerosols. Previous modeling studies DRE have been unable fully evaluate model performance due lack measurements absorption. In this study, we develop a simulation (GEOS-Chem) test it against absorption from two...
Abstract Nocturnal dinitrogen pentoxide (N 2 O 5 ) heterogeneous chemistry impacts regional air quality and the distribution lifetime of tropospheric oxidants. Formed from oxidation nitrogen oxides, N is heterogeneously lost to aerosol with a highly variable reaction probability, γ ), dependent on composition ambient conditions. Reaction products include soluble nitrate (HNO 3 or NO − nitryl chloride (ClNO ). We report first‐ever derivations wintertime aircraft measurements in critically...
Abstract. An oxidation flow reactor (OFR) is a vessel inside which the concentration of chosen oxidant can be increased for purpose studying SOA formation and aging by that oxidant. During BEACHON-RoMBAS (Bio-hydro-atmosphere interactions Energy, Aerosols, Carbon, H2O, Organics & Nitrogen–Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized OH radicals in an OFR to measure amount could formed from real mix precursor gases, how changed with time...
Abstract. Chemical transport models have historically struggled to accurately simulate the magnitude and variability of observed organic aerosol (OA), with previous studies demonstrating that significantly underestimate concentrations in troposphere. In this study, we explore two different model OA schemes within standard GEOS-Chem chemical evaluate simulations against a suite 15 globally distributed airborne campaigns from 2008 2017, primarily spring summer seasons. These include ATom,...
Abstract. From 2016 to 2018 a DC-8 aircraft operated by the US National Aeronautics and Space Administration (NASA) made four series of flights, profiling atmosphere from 180 m ∼12 km above sea level (km a.s.l.) Arctic Antarctic over both Pacific Atlantic oceans. This program, Atmospheric Tomography Mission (ATom), sought sample troposphere in representative manner, making measurements atmospheric composition each season. paper describes aerosol microphysical derived quantities obtained...
Abstract. Atmospheric marine aerosol particles impact Earth's albedo and climate. These can be primary or secondary come from a variety of sources, including sea salt, dissolved organic matter, volatile compounds, sulfur-containing compounds. Dimethylsulfide (DMS) emissions contribute greatly to the global biogenic sulfur budget, its oxidation products mass, specifically as sulfuric acid methanesulfonic (MSA). Further, is known nucleating compound, MSA may able participate in nucleation when...
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...
Significance Understanding the sources of tropospheric ozone is important for effective air quality management and accurate radiative forcing attribution. Biomass burning emits large quantities precursors to lower atmosphere. This source can drive regional-scale production, but its impact on global poorly constrained. Here, we present unique in situ aircraft observations continental pollution tracers. Ozone enhancements attributable biomass equal or exceed those from urban emissions, a...