A5062687219- Geophysics and Gravity Measurements
- Ionosphere and magnetosphere dynamics
- Earthquake Detection and Analysis
- Atmospheric chemistry and aerosols
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Atmospheric Ozone and Climate
- Advanced Chemical Sensor Technologies
- Mass Spectrometry Techniques and Applications
- Atmospheric and Environmental Gas Dynamics
- Analytical Chemistry and Chromatography
- Atmospheric aerosols and clouds
- Indoor Air Quality and Microbial Exposure
- Methane Hydrates and Related Phenomena
- Vehicle emissions and performance
- Toxic Organic Pollutants Impact
- Spectroscopy and Laser Applications
- Fire effects on ecosystems
- Catalytic Processes in Materials Science
- Isotope Analysis in Ecology
- Water Quality Monitoring and Analysis
- Analytical chemistry methods development
- Metabolomics and Mass Spectrometry Studies
- Odor and Emission Control Technologies
- Pesticide Residue Analysis and Safety
Aerodyne Research
2016-2025
Bruker (United States)
2022-2024
Cooperative Institute for Research in Environmental Sciences
2015-2023
University of Colorado Boulder
2015-2023
Billerica Public Library
2021
Tofwerk (Switzerland)
2016
University of Colorado System
2015
Institute of Noetic Sciences
2011
We evaluate the performance of a new chemical ionization source called Vocus, consisting discharge reagent-ion and focusing ion–molecule reactor (FIMR) for use in proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF) measurements volatile organic compounds (VOCs) air. The reagent ion uses low-pressure discharge. FIMR consists glass tube with resistive coating, mounted inside radio frequency (RF) quadrupole. axial electric field is used to enhance collision energies limit...
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...
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...
A list of authors and their affiliations appears at the end paper New-particle formation is a major contributor to urban smog1,2, but how it occurs in cities often puzzling3. If growth rates particles are similar those found cleaner environments (1-10 nanometres per hour), then existing understanding suggests that new should be rapidly scavenged by high concentration pre-existing particles. Here we show, through experiments performed under atmospheric conditions CLOUD chamber CERN, below...
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...
Partitioning of gas-phase organic compounds to the walls Teflon environmental chambers is a recently reported phenomenon than can affect yields reaction products and secondary aerosol (SOA) measured in laboratory experiments. Reported time scales for reaching gas-wall partitioning (GWP) equilibrium (τGWE) differ by up 3 orders magnitude, however, leading predicted effects that vary from substantial negligible. A new technique demonstrated here which semi- low-volatility oxidized (saturation...
Abstract. The impact of aerosols on climate and air quality remains poorly understood due to multiple factors. One the current limitations is incomplete understanding contribution oxygenated products, generated from gas-phase oxidation volatile organic compounds (VOCs), aerosol formation. Indeed, atmospheric gaseous chemical processes yield thousands (highly) species, spanning a wide range formulas, functional groups and, consequently, volatilities. While recent mass spectrometric...
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...
Faster than expected Iodine species are one of only a handful atmospheric vapors known to make new aerosol particles, which play central role in controlling the radiative forcing climate. He et al. report experimental evidence from CERN Cosmics Leaving Outdoor Droplets, or CLOUD, chamber demonstrating that iodic acid and iodous rapidly form particles can compete with sulfuric pristine regions. Science , this issue p. 589
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...
Aerosol affects Earth's climate and the health of its inhabitants. A major contributor to aerosol formation is oxidation volatile organic compounds. Monoterpenes are an important class compounds, recent research demonstrate that they can be converted low-volatility precursors on sub-second timescales following a single oxidant attack. The α-pinene + O3 system particularly efficient in this regard. However, actual mechanism behind conversion not understood. key challenge steric strain created...
Nitrogen oxides (NOx) play a key role in regulating the oxidizing capacity of atmosphere through controlling abundance O3, OH, and other important gas particle species. Some recent studies have suggested that particulate nitrate, which is conventionally considered as ultimate oxidation product NOx, can undergo "renoxification" via photolysis, recycling NOx HONO back to phase. However, there are large discrepancies estimates importance this channel, with reported renoxification rate constants...
Abstract. The atmospheric processes under polluted environments involving interactions of anthropogenic pollutants and natural emissions lead to the formation various complex secondary products. Therefore, characterization oxygenated organic compounds in urban areas remains a pivotal issue our understanding evolution carbon. Here, we describe measurements an iodide chemical ionization time-of-flight mass spectrometer installed with Filter Inlet for Gases AEROsols (FIGAERO-I-CIMS) both gas...
Abstract. Recent studies have demonstrated that organic compounds can partition from the gas phase to walls in Teflon environmental chambers and process be modeled as absorptive partitioning. Here these were extended investigate gas–wall partitioning of tubing inside a proton-transfer-reaction mass spectrometer (PTR-MS) used monitor compound concentrations. Rapid C8–C14 2-ketones C11–C16 1-alkenes was observed for with saturation concentrations (c∗) range 3 × 104 1 107 µg m−3, causing delays...
We present measurements of highly oxidized multifunctional molecules (HOMs) detected in the gas phase using a high-resolution time-of-flight chemical ionization mass spectrometer with nitrate reagent ion (NO3– CIMS). The took place during 2013 Southern Oxidant and Aerosol Study (SOAS 2013) at forest site Alabama, where emissions were dominated by biogenic volatile organic compounds (BVOCs). Primary BVOC represented isoprene mixed various terpenes, making it unique sampling location compared...
Abstract. Isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting, for example, 16–36 % of submicron southeastern United States (SE US) summer. Particle evaporation measurements from a thermodenuder show that volatility ambient IEPOX-SOA is lower than bulk also much known monomer tracer species, indicating...
Abstract. Losses of gas-phase compounds or delays on their transfer through tubing are important for atmospheric measurements and also provide a method to characterize quantify gas–surface interactions. Here we expand recent results by comparing different types Teflon other polymer tubing, as well glass, uncoated coated stainless steel aluminum, materials measuring the response step increases decreases in organic compound concentrations. All polymeric tubings showed absorptive partitioning...
Aromatic hydrocarbons make up a large fraction of anthropogenic volatile organic compounds and contribute significantly to the production tropospheric ozone secondary aerosol (SOA). Four toluene four 1,2,4-trimethylbenzene (1,2,4-TMB) photooxidation experiments were performed in an environmental chamber under relevant polluted conditions (NO
Severe droughts endanger ecosystem functioning worldwide. We investigated how drought affects carbon and water fluxes as well soil-plant-atmosphere interactions by tracing 13CO2 deep 2H2O label pulses volatile organic compounds (VOCs) in an enclosed experimental rainforest. Ecosystem dynamics were driven different plant functional group responses to drought. Drought-sensitive canopy trees dominated total but also exhibited the strongest response topsoil drying. Although all canopy-forming...
Yields of secondary organic aerosol (SOA) formation from oxidation volatile compounds are measured in laboratory chambers and then applied regional global models. Gas-phase losses to large Teflon-walled environmental have been recently shown reduce SOA yields. Historically, most operated batch mode. Increasingly, however, continuous flow (CF) mode is being used, which reactants products continuously introduced exhausted the chamber. Recent literature reports indicate a belief that yields CF...
Abstract The partitioning of low- and semi-volatile organic compounds into out particles significantly influences secondary aerosol formation evolution. Most atmospheric models treat as an equilibrium between gas particle phases, despite few direct measurements a large range uncertain mass accommodation coefficients (α). Here we directly measure the dynamic, isothermal specific using spectrometry in Teflon chamber. Measurements are conducted under dry humid conditions seeds different...
Abstract. Measurement techniques that provide molecular-level information are needed to elucidate the multiphase processes produce secondary organic aerosol (SOA) species in atmosphere. Here we demonstrate application of ion mobility spectrometry-mass spectrometry (IMS–MS) simultaneous characterization elemental composition and molecular structures gas particulate phases. Molecular ions gas-phase measured online with IMS–MS after ionization a custom-built nitrate chemical (CI) source. This...
The formation of secondary organic aerosol (SOA) from α-pinene ozonolysis has been widely studied, with a recent focus on contributions highly oxidized multifunctional compounds (HOMs) that have observed in laboratory and field studies. Most what is known about the chemical composition SOA HOMs, however, consists molecular formulas limited structure identification based mass spectrometric analysis. Here, we characterized formed using derivatization-spectrophotometric methods to quantify...
Abstract. In September 2017, we conducted a proton-transfer-reaction mass-spectrometry (PTR-MS) intercomparison campaign at the CESAR observatory, rural site in central Netherlands near village of Cabauw. Nine research groups deployed total 11 instruments covering wide range instrument types and performance. We applied new calibration method based on fast injection gas standard through sample loop. This approach allows calibrations timescales seconds, within few minutes an automated sequence...