Drew R. Gentner
· ProfessorVerifiedYale University · Chemical and Environmental Engineering
Active 1983–2026
About
Drew R. Gentner is a Professor of Chemical & Environmental Engineering at Yale University, with additional appointments at the School of the Environment. His research focuses on emissions and physical/chemical processes of primary and secondary air pollution, including secondary organic aerosol and ozone formation. He investigates urban air quality, emissions, composition, and chemical evolution of complex organic mixtures in the atmosphere and indoor environments, as well as non-traditional sources of reactive organic carbon and their role in air quality. Gentner develops novel instrumentation and methods to examine the spatiotemporal complexity of urban air quality and to decipher complex organic mixtures, contributing significantly to understanding the impacts of energy production and use on air pollution. His work has advanced knowledge on the emissions from various sources such as asphalt and oil sands operations, and their influence on secondary organic aerosols, as well as the transport of hazardous pollutants into indoor environments. His research has implications for improving air quality and understanding the interactions between energy, emissions, and atmospheric chemistry.
Research topics
- Chemistry
- Organic chemistry
- Environmental science
- Environmental chemistry
- Engineering
- Waste management
- Computer Science
- Chromatography
- Ecology
- Meteorology
- Environmental health
- Materials science
- Remote sensing
- Medicine
- Biology
- Physics
- Composite material
- Environmental engineering
Selected publications
Environmetrics · 2026-05-01
preprintOpen accessABSTRACT Low‐cost air pollution sensor networks are increasingly being deployed globally, supplementing sparse regulatory monitoring with localized air quality data. In some areas, like Baltimore, Maryland, there are only a few regulatory (reference) devices but multiple low‐cost sensor networks. There are many available methods to calibrate data from each network individually, including the recently proposed Gaussian process filter (GP filter) method, which mitigates the underestimation issue of other calibration methods, models spatial correlation, and yields a dynamic calibration equation. However, separate calibration of each network using a GP filter or any other calibration approach leads to conflicting air quality predictions. In this manuscript, we extend the GP filter to jointly model data from multiple low‐cost networks and reference devices. The approach provides dynamic calibrations (informed by the latest reference data) and unified predictions (combining information from all available low‐cost and reference sensors) for the entire region. This method accounts for network‐specific bias and noise, as different networks can use different types of sensors, and uses a Gaussian process to capture spatial correlations. We apply the method to calibrate PM data from Baltimore in June and July 2023 ‐ a period including days of hazardous concentrations due to wildfire smoke. Our method helps mitigate the effects of preferential sampling of one low‐cost sensor network in Baltimore, resulting in better predictions and more precise credible intervals. Our approach can be used to calibrate low‐cost air pollution sensor data in Baltimore and other areas with multiple low‐cost networks.
National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) · 2026-01-01
datasetOpen accessSenior authorIn collaboration with Yale University, scientists and engineers from NOAA conducted ground-based atmospheric NH3 concentration measurements from April 27 to October 24, 2023. In this field study, continuous and high-temporal resolution measurements of atmospheric NH3 concentrations and meteorological variables were collected at the Yale Coastal Field Station (YCFS) in Guilford, CT as part of the Atmospheric Emissions and Reactions Observed from Megacities to Marine Area (AEROMMA) campaign. The objectives of this study were to characterize the magnitude and the seasonal variability of atmospheric NH3 concentrations, as well as to evaluate the effect of wind direction in order to analyze the influence of emission sources of NH3 upwind at the YCFS located in the Long Island Sound region, which often experiences poor air quality.
Fungal emissions from air conditioning cooling coils
Indoor Environments · 2026-03-02
articleOpen accessThe fin-and-tube heat exchangers from air conditioning (AC) units are known locations of microbial growth within the built environment. Prior studies have documented the presence of potentially harmful fungal taxa on AC coils and noted the association of AC use and elevated respiratory symptoms in building occupants. This study aims to determine the rate at which fungi can be aerosolized from AC coils during normal operation. We investigated five AC units in commercial buildings in Southern CT, USA. At the end of the cooling season, we measured size-resolved aerosol concentrations (total, biological, fungal) upstream and downstream of the coils and applied ecological analysis to determine if fungal taxa on coil surfaces were emitted into downstream air. Coils were net sinks for a broad range of total aerosol sizes (0.4 to 20 μm). However, three of the five units were net emitters of bioaerosols with average emission rates of 5.6 × 10 7 to 7.2 × 10 7 biological particles hr -1 and 1.1 × 10 4 to 6.6 × 10 5 fungal spore equivalents hr -1 . Considering only measurements indicating the units as net sources, these AC units contributed approximately 34% of biological particle and 72% of airborne fungi in the downstream air. The two net sink coils were characterized by the presence of Leotiomycetes fungi , while the emitting coils had high abundance of Cladosporium , Penicillium, Aspergillus, Stachybotrys and Malassezia fungi. While most particles were found to deposit onto these coils, there is evidence that they can become net emitters of bioaerosols into air supplied indoors. • AC Coils were net sinks for a broad range of total aerosols in the upstream air. • 60% of the investigated AC units were net emitters of bioaerosols and fungi. • The non-emitting coils were characterized by Leotiomycetes and an elevated cooling load. • The emitting coil surfaces were abundant in Cladosporium , Penicillium, Aspergillus.
Ozone Formation under high NOx conditions: Insights from the AEROMMA NYC-METS field campaign
2025-03-15
preprintOpen accessSenior authorDespite well over a half century of research, gaps remain in our understanding of ozone formation chemistry. Net ozone formation results from the oxidation of NO to NO2 by peroxy radicals (HO2 and RO2) followed by photolysis of NO2. Measurements of peroxy radicals made by several analytical methods over the past decade in numerous locations across the world have revealed discrepancies under high NOx conditions ([NO] > 1 ppb), with zero-dimensional models apparently underestimating peroxy radical concentrations and ozone production rates (P(O3)) by up to a factor of eight. These findings suggest that models may misidentify when ozone formation is NOx-limited vs. NOx-saturated (VOC-limited) and that our knowledge of the relevant reactions is incomplete. To investigate these anomalously high P(O3) values at high NOx, we used the Drexel University Ethane Chemical AMPlifier (ECHAMP) instrument to measure total peroxy radicals at a roof-top site in Manhattan (NYC) as part of the NOAA AEROMMA/NYC-METS project.  A wide assortment of other measurements were made by spectroscopic and mass spectrometric methods. We will present results from this field project with special emphasis on our measurements during a few “high-NOx” periods (roughly defined as daytime periods with NO mixing ratios greater than 1 ppb).
Aerosol Science and Technology · 2025-09-12 · 1 citations
articlem), optical photothermal infrared (O-PTIR). We compare O-PTIR to existing microspectroscopy methods [Raman, fluorescence, and energy dispersive X-ray (EDX)] to study sources and aging of the complex NYC aerosol based on functional group and elemental information, which we also relate to bulk mass spectrometry methods. Single particle data shows submicron aerosol composition dominated by carbonaceous particles that fluoresce mixed with ammonium and sulfate, with a range of oxidized organic functional groups observed. At larger sizes, more primary sources (salts, dust, and biological) were observed, with nitrate being the dominant secondary anion. Collectively, the results from OPTIR and other instruments across case-study days reveal variations in sources and aging, with greater variability at larger diameters. Demonstrating the potential of O-PTIR when combined with the other methods to provide data that is important for improving air quality in urban megacities.
ACS ES&T Air · 2025-03-25
articleSenior authorCorrespondingAsphalt-related emissions are an understudied source of reactive organic compounds with the potential to form organic aerosol (OA). Ambient aerosol mass spectrometry (AMS) measurements of asphalt-related aerosols near a month-long road paving project showed enhanced ambient OA concentrations with a mix of primary and secondary OA signatures. For comparison, gas-phase emissions from real-world road asphalt samples at application (e.g., 140 °C) and in-use (e.g., 60 °C) temperatures were injected into an environmental chamber and an oxidation flow reactor to simulate varying degrees of oxidative aging while measuring their gas- and aerosol-phase oxidation products. Secondary OA formation was observed via both self-nucleation and condensation, with chemical properties dependent on asphalt temperature and reaction conditions. The chemical composition of less-aged asphalt-related OA observed in outdoor and laboratory measurements was similar to OA from other petrochemical-based sources and hydrocarbon-like OA source factors observed via AMS in previous urban studies. The composition of aged OA varied with the degree of oxidation, similar to oxidized OA factors observed in ambient air. Taken together, these field and laboratory observations suggest that contributions to urban OA during and after application may be challenging to deconvolve from other traditional sources in ambient measurements.
ACS Earth and Space Chemistry · 2025-02-19 · 1 citations
articleOpen accessThe importance of nitrate radicals (NO3) as an atmospheric oxidant is well-established. For decades, laboratory studies of multiphase NO3 chemistry have used the same methods – either NO2 + O3 reactions or N2O5 thermal decomposition – to generate NO3 as it occurs in the atmosphere. These methods, however, come with limitations, especially for N2O5, which must be produced and stored under cold and dry conditions until its use. Recently, we developed a new photolytic source of gas-phase NO3 by irradiating aqueous solutions of ceric ammonium nitrate and nitric acid. In this study, we adapted the method to maintain stable NO3 concentrations for over 24 h. We applied the method in laboratory oxidation flow reactor (OFR) experiments to measure the yield and chemical composition of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol (SOA) formed from NO3 oxidation of volatile organic compounds (VOCs) emitted by biogenic sources (isoprene, β-pinene, limonene, and β-caryophyllene) and biomass burning sources (phenol, guaiacol, and syringol). SOA yields and elemental ratios were typically within a factor of 2 and 10%, respectively, of those obtained in studies using conventional NO3 sources. Maximum SOA yields obtained in our studies ranged from 0.02 (isoprene/NO3) to 0.96 (β-caryophyllene/NO3). The highest SOA oxygen-to-carbon ratios (O/C) ranged from 0.48 (β-caryophyllene/NO3) to 1.61 (syringol/NO3). Additionally, we characterized novel condensed-phase oxidation products from syringol/NO3 reactions. Overall, the use of irradiated aqueous cerium nitrate as a source of gas-phase NO3 may enable more widespread studies of NO3-initiated oxidative aging, which has been less explored compared to that of hydroxyl radical chemistry.
Science Advances · 2025-01-03 · 7 citations
articleOpen accessSenior authorCorrespondingDry deposition is an important yet poorly constrained process that removes reactive organic carbon from the atmosphere, making it unavailable for airborne chemical reactions and transferring it to other environmental systems. Using an aircraft-based measurement method, we provide large-scale estimates of total gas-phase organic carbon deposition rates and fluxes. Observed deposition rates downwind of large-scale unconventional oil operations reached up to 100 tC hour −1 , with fluxes exceeding 0.1 gC m −2 hour −1 . The observed deposition lifetimes (τ dep ) were short enough (i.e., 4 ± 2 hours) to compete with chemical oxidation processes and affect the fate of atmospheric reactive carbon. Yet, much of this deposited organic carbon cannot be accounted for using traditional gas-phase deposition algorithms used in regional air quality models, signifying underrepresented, but influential, chemical-physical surface properties and processes. Furthermore, these fluxes represent a major unaccounted contribution of reactive carbon to downwind freshwater ecosystems that outweigh terrestrial sources, necessitating the inclusion of dry deposition in aquatic carbon balances and models.
Geophysical Research Letters · 2025-02-22 · 14 citations
articleOpen accessSenior authorCorrespondingAbstract Aqueous‐phase uptake and processing of water‐soluble organic compounds can promote secondary organic aerosol (SOA) production. We evaluated the contributions of aqueous‐phase chemistry to summertime urban SOA at two sites in New York City. The relative role of aqueous‐phase processing varied with chemical and environmental conditions, with evident daytime SOA enhancements (e.g., >1 μg/m 3 ) during periods with relative humidities (RH) exceeding 65% and often higher temperatures. Oxygenated organic aerosol (OOA) production was also sensitive to secondary inorganic aerosols, in part through their influence on aerosol liquid water. On average, high‐RH periods exhibited a 69% increase in less‐oxidized OOA production in Queens, NY. These enhancements coincided with southerly backward trajectories and greater inorganic aerosol concentrations, yet showed substantial intra‐city variability between Queens and Manhattan. The observed aqueous‐phase SOA production, even with historically low sulfate and nitrate aerosol loadings, highlights both opportunities and challenges for continued reductions in summertime PM 2.5 in urban communities.
2024-03-08
preprintOpen accessOrganic species in the atmosphere originate from a wide range of sources and processes. While real time chemical ionization mass spectrometry (CIMS) has improved our capability to characterize individual organic species in the atmosphere, the selectivity of CIMS reagent ions can limit the range of species that can be measured.  In this work the need to detect a broader range of species with a single CIMS instrument is addressed. A fast-switching bipolar time-of-flight CIMS that switches between four different reagent ions, including positive and negative ions, is demonstrated.  The performance and utility of this instrument is demonstrated by measurements obtained on board a ship in Antarctica during the PolarChange field campaign and from New York City during the AEROMMA campaign.  During both campaigns the instrument cycled through iodide (I-), benzene (C6H6+), and acetone dimer ((C3H6O)2H+) reagent ions at a 2 second data acquisition rate per cycle.  In the case of PolarChange, this combination of ions enabled simultaneous detection of trends in primary marine biological emissions such as dimethyl sulfide, nucleating species such as ammonia and methyl amine, and acids, such as nitric acid.  During AEROMMA, the fast bipolar switching capability enabled Eddy Correlation measurements of primary biogenic and urban emissions (i.e. monoterpenes and aromatics), secondary products of atmospheric oxidation (i.e. highly oxidized organics and organic nitrates), and reduced nitrogen species.  Preliminary results from this dataset, including positive matrix analyses of the combined multi-reagent ion datasets, are discussed.  Simultaneous gas and aerosol composition measurements obtained by coupling this mass spectrometer with aerosol inlets are also described.
Recent grants
NSF · $330k · 2020–2025
NSF · $100k · 2016–2018
NSF · $373k · 2018–2023
NSF · $206k · 2022–2027
Frequent coauthors
- 77 shared
A. H. Goldstein
- 35 shared
Misti Levy Zamora
University of Connecticut
- 35 shared
J. Brioude
- 32 shared
Kirsten Koehler
- 31 shared
J. B. Gilman
- 30 shared
Elena Ormeño
Centre National de la Recherche Scientifique
- 30 shared
J. A. de Gouw
Cooperative Institute for Research in Environmental Sciences
- 28 shared
Jenna C. Ditto
University of Toronto
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