A5045208985- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Atmospheric aerosols and clouds
- Atmospheric and Environmental Gas Dynamics
- Catalytic Processes in Materials Science
- Spectroscopy and Laser Applications
- Advanced Chemical Sensor Technologies
- Water Quality Monitoring and Analysis
- Toxic Organic Pollutants Impact
- Indoor Air Quality and Microbial Exposure
- Ionosphere and magnetosphere dynamics
- Per- and polyfluoroalkyl substances research
- Chemical Reaction Mechanisms
- Algal biology and biofuel production
- Molecular Spectroscopy and Structure
- Radioactive element chemistry and processing
- Chemical Reactions and Mechanisms
- Vehicle emissions and performance
- Nuclear Physics and Applications
- Odor and Emission Control Technologies
- Chromium effects and bioremediation
- Groundwater and Isotope Geochemistry
- Wind and Air Flow Studies
VA Office of Research and Development
2025
Research Triangle Park Foundation
2016-2024
Environmental Protection Agency
2017-2024
University of North Carolina at Chapel Hill
2014-2019
University of Washington
2009-2014
NOAA Earth System Research Laboratory
2013
Seattle University
2011-2012
University of Wisconsin–Eau Claire
2006
KU Leuven
2001
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...
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...
The magnitude and sources of chlorine atoms in marine air remain highly uncertain but have potentially important consequences for quality polluted coastal regions. We made continuous measurements ambient ClNO(2) Cl(2) concentrations from May 15 to June 8 aboard the Research Vessel Atlantis during CalNex 2010 field study. In Los Angeles region, was more ubiquitous than most nights study period. ranged detection limits at midday campaign maximum values night reaching 2100 200 pptv,...
Abstract. We report a new method for the simultaneous in situ detection of nitryl chloride (ClNO2) and dinitrogen pentoxide (N2O5) using chemical ionization mass spectrometry (CIMS). The technique relies on formation iodide ion-molecule clusters, I(ClNO2)− I(N2O5)−. novel N2O5 scheme is direct. It does not suffer from high variable interferences, which are associated with typical nitrate anion detection. address role water vapor, CDC electric field strength, instrument zero determinations,...
A negative‐ion proton‐transfer chemical ionization mass spectrometer was deployed on a mobile tower‐mounted platform during Nitrogen, Aerosol Composition, and Halogens Tall Tower (NACHTT) to measure nitrous acid (HONO) in the winter of 2011. High resolution vertical profiles revealed (i) HONO gradients nocturnal boundary layers, (ii) ground surface dominates production by heterogeneous uptake NO 2 , (iii) significant quantities may be deposited at night, (iv) daytime indicative or emission,...
N 2 O 5 reactivity has been measured directly for the first time on ambient aerosol particles using an entrained flow reactor coupled to a custom‐built chemical ionization mass spectrometer at two urban locations during summer. The observed is strong function of both relative humidity (RH) and particle composition. We show that particulate organic loadings, together with humidity, play leading role in determining reaction rate particles. Our values are more variable and, times, as much...
Abstract. Nitryl chloride (ClNO2) is produced at night by reactions of dinitrogen pentoxide (N2O5) on containing surfaces. ClNO2 photolyzed during the morning hours after sunrise to liberate highly reactive chlorine atoms (Cl·). This chemistry takes place primarily in polluted environments where concentrations N2O5 precursors (nitrogen oxide radicals and ozone) are high, though it likely occurs remote regions lower intensities. Recent field measurements have illustrated potential importance...
Abstract Nitryl chloride (ClNO 2 ) is a chlorine atom source and reactive nitrogen reservoir formed during the night by heterogeneous reactions of dinitrogen pentoxide on chloride‐containing aerosol particles. The main factors that influence ClNO production include oxides, ozone, surface area, soluble chloride, ambient relative humidity. Regions with strong anthropogenic activity therefore have large formation potential even inland coastal regions due to transport or local emissions...
Heterogeneous N 2 O 5 uptake onto aerosol is the primary nocturnal path for removal of NO x (= + ) from atmosphere and can also result in halogen activation through production ClNO . The coefficient has been subject numerous laboratory studies; however, only a few studies have determined ambient measurements, none focused on winter conditions, when portion removed by largest. In this work, coefficients are wintertime measurements related species at Boulder Atmospheric Observatory Weld...
Abstract Wintertime ammonium nitrate aerosol pollution is a severe air quality issue affecting both developed and rapidly urbanizing regions from Europe to East Asia. In the United States, it acute in western basins subject inversions that confine pollutants near surface. Measurements modeling of wintertime episode Salt Lake Valley, Utah, demonstrate closely related photochemical ozone through common parameter, total odd oxygen, O x,total . We show traditional nitrogen oxide volatile organic...
Abstract We present OH observations from Nitrogen, Aerosol Composition, and Halogens on a Tall Tower 2011 (NACHTT‐11) held at the Boulder Atmospheric Observatory in Weld County, Colorado. Average levels noon were ~ 2.7 × 10 6 molecules cm −3 2 m above ground level. Nitrous acid (HONO) photolysis was dominant source (80.4%) during this campaign, while alkene ozonolysis (4.9%) ozone (14.7%) smaller contributions to production. To evaluate recycling sources of HO RO , an observationally...
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...
Abstract The Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) field experiment took place during late winter, 2011, at site 33 km north of Denver, Colorado. study included fixed‐height measurements aerosols, soluble trace gases, volatile organic compounds near surface level, as well vertically resolved nitrogen oxides, aerosol composition, gas‐phase acids, halogen species from 3 to 270 m above ground level. There were 1928 individual profiles the three‐week campaign...
The sea breeze/land breeze diurnal circulation within the Los Angeles Basin and adjacent waters transports marine air into basin during day urban to Santa Monica Bay night. Nitryl chloride, ClNO 2 is a nocturnal trace gas formed from heterogeneous reaction of dinitrogen pentaoxide (N O 5 ) with chloride containing aerosol. Its photolysis after sunrise produces atomic chlorine radicals regenerates NO , both which may increase ozone production. Mixing source salt x in provides conditions ideal...
The rates of heterogeneous reactions trace gases with aerosol particles are complex functions particle chemical composition, morphology, and phase state. Currently, the majority model parametrizations reaction kinetics focus on population average mass, assuming that individual have same composition as Here we assess impact mixing state using N2O5 reactive uptake coefficient, γ(N2O5), dependence particulate chloride-to-nitrate ratio (nCl(-)/nNO3(-)). We describe first simultaneous ambient...
Abstract. We present measurements utilizing the Filter Inlet for Gases and Aerosols (FIGAERO) applied to chamber of isoprene-derived epoxydiol (IEPOX) reactive uptake aqueous acidic particles associated secondary organic aerosol (SOA) formation. Similar recent field observations with same instrument, we detect two molecular components desorbing from IEPOX SOA in high abundance: C5H12O4 C5H10O3. The thermal desorption signal former, presumably 2-methyltetrols, exhibits distinct maxima,...
Abstract. An experimental approach for the direct measurement of trace gas reactivity on ambient aerosol particles has been developed. The method utilizes a newly designed entrained flow reactor coupled to custom-built chemical ionization mass spectrometer. is described via application N2O5 reaction probability, γ (N2O5). Laboratory investigations well characterized show that measurements (N2O5) observed with this technique are in agreement previous observations, using conventional tube...
Abstract. Direct measurements of N2O5 reactivity on ambient aerosol particles were made during September 2009 at the Scripps Institution Oceanography (SIO) Pier facility located in La Jolla, CA. using a custom flow reactor and particle modulation technique alongside size distributions non-refractory composition. The pseudo-first order rate coefficients derived from surface area concentrations used to determine population average reaction probability, γ(N2O5), approximately every 50 min....
During the Nitrogen, Aerosol Composition, and Halogens on a Tall Tower campaign at National Oceanic Atmospheric Administration Boulder Observatory tower, Erie, CO, USA, in winter 2011, soluble trace gases, ionic composition of size‐resolved aerosols, associated meteorological conditions were measured. Median gas‐phase mixing ratios HCl, HNO 3 , NH 0.072, 0.202, 5.79 nmol mol −1 respectively. Most aerosol Cl − was with supermicrometer size fractions whereas NO 4 + primarily submicrometer...
Abstract. Isomeric epoxydiols from isoprene photooxidation (IEPOX) have been shown to produce substantial amounts of secondary organic aerosol (SOA) mass and are therefore considered a major isoprene-derived SOA precursor. Heterogeneous reactions IEPOX on atmospheric aerosols form various aerosol-phase components or "tracers" that contribute the burden. A limited number reaction rate constants for these acid-catalyzed aqueous-phase tracer formation constrained through bulk laboratory...
Per- and polyfluoroalkyl substances (PFAS) are incorporated into an ever-increasing number of modern products inevitably enter the environment ultimately human bodies. Herein, we show that chemical ionization mass spectrometry with iodide reagent ion chemistry is a useful technique for detection fluorotelomer alcohols (FTOHs) other oxygenated PFAS, including per- polyfluoro carboxylic acids such as hexafluoropropylene oxide dimer acid. This offers direct, high-time resolution measurement...
Given the extent to which per- and polyfluoroalkyl substances (PFAS) are used in commercial industrial applications, need evaluate treatment options that reduce environmental emissions human ecological exposures of PFAS is becoming more necessary. One specific chemical class PFAS, fluorotelomer alcohols (FTOHs), have vapor pressures such a significant fraction expected be present gas-phase even at ambient temperatures. FTOHs variety including synthesis material coatings. Using two...