About

Daven Henze is an Associate Professor and the Associate Chair of the Graduate Program in the Paul M. Rady Mechanical Engineering department at the University of Colorado Boulder. His research interests include aerosols, air quality, climatology, and atmospheric chemistry. He is involved in advancing understanding in these areas through his academic and research activities, contributing to the fields of environmental engineering and atmospheric sciences.

Research topics

• Environmental science
• Geography
• Meteorology
• Geology
• Environmental health
• Atmospheric sciences
• Climatology
• Engineering
• Physics
• Ecology
• Environmental chemistry
• Environmental protection
• Chemistry
• Medicine
• Remote sensing

Selected publications

• Is There an Optimal Wavelength for Germicidal Ultraviolet Air Disinfection?

  Environmental Science & Technology · 2026-03-06

  articleOpen 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. GUV light sources at other wavelengths are being actively developed, creating an urgent need for guidance on their relative advantages. 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 242 nm than above it. This is mainly due to O3 production through O2 photolysis below 242 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 equiv air changes per hour (eACH), pollution risk below 242 nm is also at least ∼20 times that above 242 nm. At very high disinfection rates such as 20 eACH, the difference between the ratios below and above 242 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 pollution. 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 pollution, and logistic requirements), and these trade-offs should be considered in different situations to maximize the overall benefit. The use of Far UVC may require simultaneous deployment of air cleaning for pollution mitigation.

  PublisherDOI

• National climate action can ameliorate, perpetuate, or exacerbate international air pollution inequalities

  Nature Communications · 2026-01-26

  articleOpen accessSenior author

  Climate action ameliorates public health by reducing hazardous air pollutants alongside greenhouse gases, yet misguided mitigation efforts could induce imbalances in air pollution exchange across international borders. Despite its potential to endanger equality, the effects from climate action on transboundary air pollution are relatively unstudied. Here we show that stricter mitigation increases the fraction of co-benefits that originate externally in Africa by +8% in shared socioeconomic pathways (SSP) towards sustainability (SSP1) and by +53% for fragmentation (SSP3). The fraction of externally originating co-benefits is greater in developing countries (0.76 in SSP1-26) than developed (0.65), indicating that developing countries are more dependent on external action. Although co-benefits are maximized in the most ambitious scenario, SSP1-19 (1.32 million deaths avoided), their transboundary exchange between countries varies. These results suggest a need for climate policies that consider how inequalities in transboundary air pollution evolve across distinct socioeconomic trends and mitigation strategies in addition to total co-benefit estimates.

  PublisherOA PDFDOI

• Supplementary material to "Do GEMS geostationary satellite observations of tropospheric NO ₂ always improve NO _x emission estimates and related air quality modelling?"

  2026-04-01

  articleOpen access
  PublisherDOI

• Do GEMS geostationary satellite observations of tropospheric NO ₂ always improve NO _x emission estimates and related air quality modelling?

  2026-04-01

  articleOpen access

  Abstract. Satellite observations of atmospheric composition from low Earth orbit (LEO) have significantly advanced our understanding of global tropospheric chemistry; however, their 12-hour overpass cadence limits the attribution of rapid compositional changes. The launch of the Korean Geostationary Environment Monitoring Spectrometer (GEMS) in 2020 heralded the beginning of continuous spaceborne monitoring of atmospheric composition during sunlit hours across Asia, allowing researchers to track atmospheric variability in real-time from a geostationary perspective. We assess the added value of GEMS observations of tropospheric NO2 to estimate monthly emissions of NOx across Asia compared with the information provided by the equivalent instrument in LEO. We use the adjoint of the GEOS-Chem atmospheric chemistry transport model to infer NOx emissions, comparing estimates using the full set of GEMS tropospheric NO2 data against a surrogate LEO dataset created by subsampling the GEMS data at 13:45 local time (Korea Standard Time, KST). We find that the benefits of assimilating high-frequency GEMS observations are most significant during non-summer months (September−May), when elevated NO2 concentrations and pronounced diurnal variability provide strong constraints on emission estimates. During this period, NOx emission estimates derived from the full GEMS record deviate substantially from LEO-proxy results, with differences of 0.2−52.6 GgN month−1, corresponding to 0.02−5.06 % of the a priori emissions. These differences further propagate into widespread adjustments in modelled ozone, hydroxyl radicals, and other secondary species, with evaluation against independent in situ measurements showing that GEMS-inferred emission estimates offer comparable or superior performance particularly in regions where the differences are most pronounced. In contrast, we find that during summer months (June−August), low NO2 levels likely introduce retrieval uncertainties that challenge the data assimilation framework in which only anthropogenic NOx sources are optimised, leading to negligible or even detrimental impacts on our ability to estimate NOx emissions.

  PublisherOA PDFDOI

• Global CO emissions and drivers of atmospheric CO trends constrained by MOPITT satellite measurements

  Atmospheric chemistry and physics · 2026-04-23

  articleOpen access

  Abstract. Carbon monoxide (CO), an important atmospheric pollutant produced by incomplete combustion and hydrocarbon oxidation, significantly affects atmospheric oxidation capacity and air quality. Accurate quantification of its global emissions and the underlying driver behind its atmospheric trends is essential for understanding changes in global atmospheric environment. Using 20 years (2003–2022) of data from the Measurement of Pollution in the Troposphere (MOPITT) instrument, we analyze changes in global CO emissions and atmospheric concentrations by applying a four-dimensional variational (4D-Var) assimilation framework within the GEOS-Chem adjoint model. A posteriori simulations show good agreement with independent surface and aircraft measurements compared to a priori simulations. Sensitivity analyses further confirm that inferred emissions remain robust against uncertainties associated with satellite vertical sensitivity and variations in hydroxyl radical (OH) concentrations. Our results indicate a substantial decline in global anthropogenic CO emissions of 14 %–17 % (approximately 85–110 Tg yr−1) over the two-decade period, largely driven by emission reductions in the United States, Europe, and eastern China. Biomass burning emissions exhibited strong interannual variability, with recent increases in Northern Hemisphere high-latitude forests; in particular, the intense 2021 wildfires substantially offset the anthropogenic emission-driven decline in atmospheric CO over the Northern Hemisphere. This study provides a comprehensive assessment of global CO emissions and the mechanisms governing atmospheric CO trends, offering a scientific basis for integrated policies addressing both air pollution and climate change.

  PublisherDOI

• 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

• A Graph Theory-Based Algorithm for the Reduction of Atmospheric Chemical Mechanisms

  ChemRxiv · 2025-03-17

  preprintOpen access

  The atmospheric chemistry of volatile organic compounds (VOC) has a major influence on atmospheric pollutants and particle formation. Accurate modeling of this chemistry is essential for air quality models. Complete representations of VOC oxidation chemistry are far too large for spatiotemporal simulations of the atmosphere, necessitating reduced mechanisms. We present Automated MOdel REduction version 2.0 (AMORE 2.0), an algorithm for the reduction of any VOC oxidation mechanism to a desired size by removing, merging, and rerouting sections of the graph representation of the mechanism. We demonstrate the algorithm on isoprene (398 species) and camphene (100,000 species) chemistry. We remove up to 95% of isoprene species while improving upon prior reduced isoprene mechanisms by 53-67% using a multi-species metric. We remove 99% camphene species while accurately matching camphene secondary organic aerosol production. This algorithm will bridge the gap between large and reduced mechanisms, helping to improve air quality models.

  PublisherOA PDFDOI

• Sources of PM2.5 exposure and health benefits of clean air actions in Shanghai

  Environment International · 2025-01-01 · 4 citations

  articleOpen access

  • Shanghai’s PM 2.5 health burden is most affected by emissions in other provinces. • Shanghai’s PM 2.5 health burden is most sensitive to control of NH 3 emissions. • Benefits of per-unit decreases in NO x emissions increase in 2019 compared to 2013. • Clean Air Actions avoid 3,132 early deaths in Shanghai in 2019 relative to 2013. Estimating PM 2.5 exposure and its health impacts in cities involves large uncertainty due to the limitations of model resolutions. Consequently, attributing the sources of PM 2.5 -related health impacts at the city level remains challenging. We characterize the health impacts associated with chronic PM 2.5 exposure and anthropogenic emissions in Shanghai using a chemical transport model (GEOS-Chem) and its adjoint. By incorporating high-resolution satellited-derived PM 2.5 estimates into the calculation, we investigate the response of PM 2.5 exposure and its related health impacts in Shanghai to changes in anthropogenic emissions from each individual region, species, sector, and month. We estimate that a 10% decrease in anthropogenic emissions throughout China avoids over 752 (506–1,044) PM 2.5 -related premature deaths in Shanghai, with changes in local emissions potentially saving 241 (161–334) lives. Ammonia (NH 3 ) emissions are identified as the marginal dominant contributor to the health impacts due to the NH 3 -limited PM 2.5 formation within the city, thus controlling NH 3 emissions at both the local and regional scales are effective at reducing the population’s exposure to PM 2.5 . A negative response of the PM 2.5 exposure to local nitrogen oxides (NO x ) emission changes is detected in winter. Even so, controlling NO x emissions is still justified since the negative impacts decrease as anthropogenic emissions decline and NO x emission reductions benefit the public health on average. The anthropogenic emission changes due to Clean Air Actions helped avoid 3,132 (2,108–4,346) PM 2.5 -related premature deaths in 2019 relative to 2013, most of which are associated with emission reductions in the agricultural and industrial sectors.

  PublisherDOI

• Sector-, Season-, and Country-Specific NO₂-Associated Health Benefits from NO_<i>x</i> Emission Reductions

  ACS ES&T Air · 2025-03-19 · 1 citations

  articleOpen access

  Long-term exposure to NO2 is associated with elevated risks for pediatric asthma and premature death. Despite national policies targeting NO2’s main source, NOx emissions, its global health burden remains high. Here, we use the air quality model GEOS-Chem adjoint with TROPOspheric Monitoring Instrument (TROPOMI)-based satellite downscaling to estimate that long-term NO2 exposure is responsible for 2.07 (95% CI 0.91–2.70) million pediatric asthma cases and 1.98 (95% CI 0.52–2.86) million deaths globally in 2019. We attribute these to anthropogenic NOx emissions by sector, country, and season using the adjoint model and provide a recommendation for the most impactful sector and season for NOx emission controls in each G20 country. Discrepancies exist between the health benefits incurred by emission reductions and the emission sector distributions, particularly in countries with emitters adjoining population centers. For example, we find that, if Russian anthropogenic NOx emissions were reduced uniformly by 10% across all sectors, the energy sector, 31% of annual NOx emissions, would account for 47% of pediatric asthma and 49% of premature death health benefits. The season in which these emission reductions occur also affects the magnitude of the health benefit, as seen by the fact that Russian wintertime NOx emission reductions alone are responsible for approximately one-third of the annual health benefits for each health outcome. We present the unique results for each of the G20 members to showcase how a country’s NOx emission reductions can be most impactful in reducing the global NO2-associated health burden.

  PublisherOA PDFDOI

• Tracking Ethane From Space Over a Large US Oil and Gas Region

  Geophysical Research Letters · 2025-07-04

  articleOpen access

  Abstract Ethane (C 2 H 6 ) is a volatile organic compound (VOC) that has few anthropogenic sources, and is primarily emitted from oil and natural gas (NG) (O&amp;G) activities. This makes it a useful tracer for distinguishing O&amp;G activities from other sources of methane (CH 4 ) and non‐methane VOCs. Here we use the Cross‐track Infrared Sounder (CrIS) to develop a simple physical approach that quantifies the change in C 2 H 6 absorption over the Permian basin. However, aircraft observations and the magnitude of the gradient in absorption across the basin suggests our model underestimates C 2 H 6 emissions by a factor of ∼2. The 2014–2020 trend in C 2 H 6 absorption is found to be increasing 5.6% ± 3.8% yr −1 , which suggests that the amount of VOCs emitted per amount of NG production has decreased by 23% yr −1 .

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: SNOWpack Photodenitrification from the Antarctic and Arctic Cryosphere (SNOWPAAC)

  NSF · $57k · 2013–2015

Frequent coauthors

• Zhen Qu

  North Carolina State University

  109 shared

• Dylan B. A. Jones

  University of Toronto

  81 shared

• K. W. Bowman

  Jet Propulsion Laboratory

  75 shared

• Randall V. Martin

  Washington University in St. Louis

  64 shared

• Susan C. Anenberg

  62 shared

• Jesse O. Bash

  Research Triangle Park Foundation

  62 shared

• Shannon L. Capps

  Stanford University

  55 shared

• Nicolas Theys

  50 shared

Labs

• Henze GroupPI