About

Joost de Gouw is a Professor and Chair at the University of Colorado Boulder, affiliated with the Institute Fellow of CIRES (Cooperative Institute for Research in Environmental Sciences). His educational background includes a MSc in Physics and a PhD in Physics from the University of Utrecht, Netherlands, with his PhD awarded cum laude. He completed postdoctoral fellowships at JILA, University of Colorado Boulder, and NOAA Aeronomy Laboratory. His research focuses on atmospheric chemistry, specifically the emissions, chemistry, and loss processes of organic carbon in both the gas and particle phases in the Earth's atmosphere. He investigates the formation of secondary pollutants such as ozone and aerosol and their influence on air quality and climate. De Gouw develops and utilizes mass spectrometric and other measurement methods for volatile organic compounds and analyzes satellite remote sensing data related to Earth's atmospheric composition. His work contributes to understanding air quality, climate change, and the impact of various emission sources on atmospheric chemistry.

Research topics

• Environmental science
• Chemistry
• Atmospheric sciences
• Meteorology
• Climatology
• Environmental chemistry
• Geography
• Organic chemistry
• Geology
• Oceanography
• Geomorphology
• Waste management
• Photochemistry
• Ecology
• Cartography
• Physics

Selected publications

• Supplementary material to "Isomer-resolved online analysis of organic aerosols using ion mobility mass spectrometry"

  2026-04-10

  articleOpen access
  PublisherDOI

• Emission Characteristics of Volatile Organic Compounds and Organic Aerosol Evolution with OH Exposure in Seoul During Winter

  ACS ES&T Air · 2026-04-10

  articleOpen accessSenior author

  This study characterizes wintertime volatile organic compound (VOC) emissions, oxidative aging, and secondary organic aerosol (SOA) formation in Seoul using high-resolution, real-time measurements. Anthropogenic VOCs, particularly BTEX, dominated emissions under stagnant meteorological conditions with shallow boundary layers. Two hydrocarbon photochemical clocks provided complementary aging metrics: the reactive [benzene]/[TMB] ratio captured fresh, rapidly oxidized local air masses, while the slower [benzene]/[toluene] ratio reflected aged, regionally transported air─with distinct diurnal patterns confirming this dual character. SOA/OA ratios correlated more strongly with OH exposure (OHexp) from the [benzene]/[TMB] clock, highlighting short-lived aromatics as key local SOA drivers. Compositional analysis revealed a sequential SOA evolution continuum: rapid initial formation of less-oxidized OA (LO-OOA) followed by progressive aging into more-oxidized OA (MO-OOA). A semiempirical volatility basis set (VBS) model reproduced observed SOA temporal trends (R2 = 0.53–0.58), capturing 50–60% of ambient SOA mass from measured precursors alone─driven by cold winter temperatures and abundant reactive aromatics. Systematic underestimation during peak pollution events highlights the need to explicitly account for intermediate-volatility organic compounds (IVOCs) from cold-start emissions and multigenerational aging mechanisms to close the wintertime urban SOA mass gap.

  PublisherDOI

• Isomer-resolved online analysis of organic aerosols using ion mobility mass spectrometry

  2026-04-10

  articleOpen access

  Abstract. Secondary organic aerosol (SOA) makes up much of the particulate matter in the troposphere and impacts global climate and human health, though uncertainties regarding the sources and properties of SOA limit our understanding of these effects. New analytical techniques are required to better characterize the molecular composition of SOA, including methods that can identify isomeric compounds that may have different contributions to SOA properties such as hygroscopicity or volatility. We present a method for isomer-resolved analysis of SOA using a commercially available chemical ionization ion-mobility time-of-flight mass spectrometer (CI-IMS-TOF) and a Vaporization Inlet for Aerosols (VIA). The compatibility of the VIA and the CI-IMS-TOF was assessed through the analysis of 10 carboxylic acid standards across a large temperature range (30 - 170 °C). Ion drift times were found to be stable to within 0.075% of their initial values after drift time calibration. The VIA-CI-IMS-TOF was also used to collect real-time ion mobility and mass spectra of SOA constituents during an α-pinene ozonolysis chamber experiment. Several reaction products were identified in the SOA using synthetic standards, including structural isomers of C8H12O4 and C9H14O4. Temporal evolution of reaction products was used to assess formation timescales and determine the generation of oxidation for individual isomers. Both iodide and bromide reagent ions were used in the VIA-CI-IMS-TOF to achieve a more comprehensive analysis of SOA. This study demonstrates the performance of the VIA-CI-IMS-TOF for online, isomer-resolved analysis of organic aerosol and its potential for improving the current understanding of SOA composition.

  PublisherOA PDFDOI

• Secondary organic aerosol in urban China: A distinct chemical regime for air pollution studies

  Science · 2025-08-28 · 28 citations

  reviewOpen access

  In the past decades, China has witnessed high air pollution associated with rapid economic development, although regulatory efforts have alleviated the situation since 2013. Haze events characterized by high particulate matter (PM) levels in China are not only of enormous magnitude but also represent a distinct chemical regime. Once driven by direct emissions, these high-PM episodes are now more affected by secondary aerosol, especially secondary organic aerosol (SOA). This Review synthesizes the state of the science of SOA formation in urban China, specifically (i) how the dominance of anthropogenic precursors affects SOA formation, (ii) what are the prevailing SOA formation mechanisms, and (iii) how important are the multipollutant and multiphase processes in SOA formation and evolution. We also highlight essential directions for future studies.

  PublisherOA PDFDOI

• Deep transfer learning method for seasonal TROPOMI XCH ₄ albedo correction

  Atmospheric measurement techniques · 2025-04-11 · 2 citations

  articleOpen accessSenior author

  Abstract. The retrieval of methane from satellite measurements is sensitive to the reflectance of the surface, and in many regions, especially those with agriculture, surface reflectance depends on the season. Existing corrections for this effect do not take into account a changing relationship between reflectance and the methane correction value over time. It is an important issue to consider, as agricultural emissions of methane are significant and other sources, like oil and gas production, are also often located in agricultural lands. In this work, we use a set of 12 monthly machine learning models to generate a seasonally resolved surface albedo correction for TROPOspheric Monitoring Instrument (TROPOMI) methane data across the Denver–Julesburg basin. We found that land cover is important in the correction, specifically the type of crops grown in an area, with drought-resistant-crop-covered areas requiring a correction of 5–6 ppb larger than areas covered in water-intensive crops in the summer. Additionally, the correction over different land covers changes significantly over the seasonally resolved timescale, with corrections over drought-resistant crops being up to 10 ppb larger in the summer than in the winter. This correction will allow for more accurate determination of methane emissions by removing the effect of agricultural and other seasonal effects on the albedo correction. The correction may also allow for the deconvolution of agricultural methane emissions, which are seasonally dependent, from oil and gas emissions, which are more constant in time.

  PublisherDOI

• Complex Effects of Reduced Mobile Source Emissions on Submicron Particulate Matter Concentrations in Los Angeles

  ACS ES&T Air · 2025-12-31

  articleOpen access

  Despite considerable reductions in mobile source emissions, annual average aerosol concentrations measured in Los Angeles using Federal Reference Methods (FRM) have not appreciably declined over the past decade. Here, we use submicron aerosol measurements and zero-dimensional modeling to quantify the impacts of these emission reductions on aerosol formation in Pasadena, CA, during the late spring and summer of 2022. Reductions in secondary organic aerosol (SOA) concentrations expected from reduced mobile source emissions appear to have been largely offset by increases in hydroxyl radical concentrations, an indirect effect of reduced nitrogen oxide (NOx) emissions. As a result, while the predicted contribution of mobile sources to the SOA burden has declined from ∼50% in 2010 to only ∼25% in 2022, concentrations of locally formed SOA have remained relatively constant. In contrast, reductions in mobile source NOx emissions have likely reduced overnight production of nitric acid and ammonium nitrate (AN) aerosol. We provide indirect evidence that FRM measurements may have failed to capture the reduction in AN since 2010 due to the evaporation of semivolatile species from FRM filter samples. Our results suggest that given the effectiveness of historical regulatory efforts aimed at mobile sources, and on-road sources in particular, additional reductions in submicron aerosol concentrations in Los Angeles will likely require increased focus on abating emissions from nonroad and area sources.

  PublisherOA PDFDOI

• Is there an optimal wavelength for germicidal ultraviolet air disinfection?

  ChemRxiv · 2025-04-11

  preprintOpen access

  Germicidal UV (GUV) disinfection is effective against airborne pathogens, but it has been recently reported to increase indoor air pollution. Conventional GUV at 254 nm is applied in the upper room only due to skin/eye safety limits, while “Far UVC” (e.g. at 222 nm) is applied across the whole room due to less restrictive safety limits, enabling simpler installation and disinfection. We investigate GUV between 185 and 310 nm by modeling, in search of an optimal wavelength with both high disinfection and safety. For a specific fluence rate, GUV-induced air pollution health risks are at least ~20 times larger below 245 nm than above it. This is mainly due to O3 production through O2 photolysis below 245 nm, with a contribution from particulate matter formation from enhanced volatile organic compound oxidation. When normalized to a constant CDC-recommended disinfection rate of 5 equivalent air changes per hour (eACH), pollution risk below 245 nm is also at least ~20 times that above 245 nm. At very high disinfection rates such as 20 eACH, the difference between the ratios below and above 245 nm is smaller, but still a factor of ~20. Our results show a clear advantage of upper-room GUV vs. Far UVC for indoor air quality. These results appear robust despite substantial uncertainties in absolute disinfection efficiencies, which are a critical limitation for widespread GUV application. Thus, there is no optimal GUV wavelength across all important criteria (exposure limits, disinfection efficiency, indoor air quality, and logistic requirements), and these tradeoffs should be considered in different situations to maximize the overall benefit. Use of Far UVC may require simultaneous deployment of air cleaning for pollution. As new practical UV light sources at wavelengths other than 222 and 254 nm keep being developed, this study provides guidance for evaluating and selecting wavelength(s) for GUV air disinfection.

  PublisherOA PDFDOI

• Deconvolution of Partitioning Delays from Time-Resolved Trace Gas Measurements

  ACS ES&T Air · 2025-09-10

  article

  Time-resolved measurements of low-volatility gas-phase compounds are limited by partitioning of the analyte to instrument surfaces, resulting in what are known as partitioning delays. These delays slow instrument responses and affect the accuracy of subsequent analyses. In this work, we introduce a deconvolution algorithm that corrects measurements affected by partitioning delays. We evaluate the performance of this algorithm using synthetic data and also demonstrate its utility in correcting partitioning delays in airborne nitric acid measurements. We compare the effectiveness of deconvolution to the current best practice for partitioning delays: frequent subtraction of instrument background. Frequent background measurements are outperformed by the deconvolution algorithm when sample concentrations are changing faster than the instrument response time. The deconvolution algorithm can be applied to time series that include frequent measurement of instrument backgrounds, enabling reanalysis of past data. Furthermore, the algorithm does not rely on any coincident data; it is effective without any external information about the true time series of an analyte. When applied to nitric acid measurements from a wildfire smoke plume, deconvolution increases the calculated normalized excess mixing ratio (ΔHNO3/ΔCO) by 72%. We conclude that the deconvolution algorithm is applicable to ground, airborne, and eddy covariance measurements of “sticky” compounds.

  PublisherDOI

• Atmospheric Evolution of Brown Carbon from Wildfires in North America

  Environmental Science & Technology · 2025-08-07 · 3 citations

  article

  Atmospheric brown carbon (BrC) from wildfires is a key component of light-absorbing carbon that significantly contributes to global radiative forcing, but its atmospheric evolution and lifetime remain poorly understood. In this study, we investigate BrC evolution by synthesizing data from one laboratory campaign and four aircraft campaigns spanning diverse spatial scales across North America. To estimate initial conditions for evaluating plume evolution, we develop a method to parametrize the emission ratios of BrC and other species using commonly measured inert tracers, acetonitrile and hydrogen cyanide. The evolution of BrC absorption in the free troposphere is characterized as a function of hydroxyl radical (OH) exposure, yielding an effective photochemical rate constant of 9.7–1.6+4.8 × 10–12 cm3 molecule–1 s–1. The relatively slow reaction rate results in small BrC decay within the first few hours after emission, making it difficult to distinguish from source variability. This helps explain the absence of clear evolutionary trends in near-field studies. Assuming an OH concentration of 1.26 × 106 molecules cm–3, this rate constant corresponds to an e-folding lifetime of approximately 23 h. After extensive photooxidation (OH exposure ∼1012 molecules cm–3 s), 4 ± 2% of the emitted BrC persists, representing a recalcitrant fraction with potential long-term climate impacts. These results improve our understanding of BrC variability and photochemical processing and provide critical constraints for modeling its impacts on climate.

  PublisherDOI

• Secondary Organic Aerosol Yields from NO ₃ Oxidation of Phenolic, Aromatic, and Heterocyclic VOCs: Implications for Biomass Burning Plumes

  ACS ES&T Air · 2025-10-04

  article

  Biomass burning secondary organic aerosol (BBSOA) has become an important research area in atmospheric science, particularly due to the ongoing global increase in wildfire activity. BBSOA can form from the reactions of emitted volatile organic compounds (VOCs) and gas-phase evaporated primary organic aerosols (POA) with atmospheric oxidants such as O3, OH, and NO3. While some studies have examined SOA formation from OH during daytime BB events, fewer have considered the potentially significant role of NO3. In this chamber study, vapor wall loss (VWL)-corrected SOA yields from the NO3 oxidation of five known BBVOCs: catechol, phenol, styrene, furfural, and methyl furfural are reported. SOA from NO3 reactions of phenol, furfural, and methyl furfural have not been previously reported, to our knowledge. VWL corrections increased the measured SOA yield by 30–41% across an OA range of ∼5 to ∼500 μg m–3, which represents aerosol concentrations from dilute to concentrated biomass burning plumes. Catechol had the highest yield at OA = 100 μg m–3 (1.5), followed by furfural (0.17) and styrene (0.17), with phenol (0.08) and methyl furfural (0.10) having the lowest yields. A wildfire case study is also presented to illustrate the importance of both evaporation and chemistry in understanding BB aerosol composition, though their relative importance is highly dependent on oxidant concentrations, temperature, and dilution rates. Finally, an extractive electrospray soft ionization mass spectrometer (EESI) was used to obtain data on potential molecular species in each experiment, and the nitrocatechol mass yield for the reaction of catechol with NO3 is determined to be 0.90 ± 0.35.

  PublisherDOI

Recent grants

• Evolution in Secondary Organic Aerosol Formation in Urban Atmosphere

  NSF · $941k · 2022–2026

• New Mass Spectrometer Technology for Analysis of Biogenic Volatile Organic Compounds (VOCs)

  NSF · $410k · 2006–2010

Frequent coauthors

• C. Warneke

  NOAA Chemical Sciences Laboratory

  1963 shared

• J. B. Gilman

  895 shared

• B. M. Lerner

  Aerodyne Research

  627 shared

• Abigail R. Koss

  592 shared

• P. R. Veres

  National Oceanic and Atmospheric Administration

  569 shared

• W. C. Kuster

  National Oceanic and Atmospheric Administration

  551 shared

• Jeff Peischl

  National Oceanic and Atmospheric Administration

  544 shared

• J. S. Holloway

  National Oceanic and Atmospheric Administration

  542 shared

Education

• M.S., Physics

  University of Utrecht

  1990

• Ph.D., Physics

  University of Utrecht

  1994

• Other

  JILA, University of Colorado Boulder

  1994

• Other

  NOAA Aeronomy Laboratory

  1997

Awards & honors

• Award for Excellence In Research, Scholarly and Creative Wor…
• Co-recipient, Colorado Governor's Award for High-Impact Rese…
• Healthy Community Award, Boulder County Public Health (2022)
• Fellow of the American Geophysical Union (2020)
• Web of Science Highly Cited Researcher in the category Cross…