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Ryan Sullivan - Carnegie Mellon University. Pittsburgh, PA, US

Ryan Sullivan

Professor | Carnegie Mellon University


Ryan Sullivan's research includes developing aircraft-deployable analytical instrumentation to characterize particles in the atmosphere.


Ryan Sullivan has a background in atmospheric and analytical chemistry, single-particle analysis, heterogeneous kinetics and cloud nucleation research. His research interests include the development of improved aircraft-deployable analytical instrumentation to characterize individual particles in the atmosphere in real-time. These instruments are used to investigate the physicochemical properties of atmospheric particles emitted and produced from a variety of sources, the chemical processes they experience during atmospheric transport, and how these processes modify the ability of particles to nucleate both cloud droplets and ice crystals, thus altering cloud properties and the Earth’s climate. These research endeavors involve equal parts instrument development, laboratory experiments and field measurements.

Areas of Expertise (7)

Water Treatment

Phase Transitions

Environmental Systems

Aerosol-Cloud Interactions

Air Quality

Microfluidic Systems

Mass Spectrometry

Media Appearances (5)

If you can smell your air freshener, you might have a problem

The Washington Post  online


“To a chemist ‘really clean’ would actually be no scent because the scent is caused by a chemical,” said Ryan Sullivan, an associate professor of chemistry and mechanical engineering at Carnegie Mellon University. “Truly clean means very low levels of chemicals.”

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The Discovery Files: Fire & Ice

National Science Foundation  online


Scientists at Carnegie Mellon University investigated the effects wildfires have on cloud formation and the intense storms that can develop from them.

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Dead orangutans and burnt forests: Nature lovers see the ravages of climate change up close

Salon  online


"I remember waking up to a smoke-filled apartment as I had left the window open in my bedroom at night, and suddenly realizing what the deep red sky I noticed at sunset the night before had really meant – it was caused by the smoke particles in the atmosphere that hadn't yet reached me but were on the way," Ryan Sullivan, associate professor of chemistry and mechanical engineering at Carnegie Mellon University's College of Engineering, wrote to Salon about his experience in the first month of his PhD program in chemistry at the University of California — San Diego. A large wildfire had broken out in the San Diego area.

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COVID and Masks

Shared Air Podcast  online


We discuss how masks can help prevent the spread of COVID with guests Coty Jen and Ryan Sullivan. Coty and Ryan also tell us about their project to help protect nurses and doctors when treating COVID patients.

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'Tweezers' Show How Particles Evolve in the Atmosphere

Futurity  online


"Particles float around in the atmosphere for at least a week on average," researcher Ryan Sullivan says. "They're so dynamic—their composition and other properties are constantly evolving."

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Ryan Sullivan: Studying Atmospheric Particles Using Aerosol Optical Tweezers Ryan Sullivan: Understanding Climate Change Through Clouds



Industry Expertise (2)

Environmental Services


Education (3)

University of California at San Diego: Ph.D., Chemistry 2008

University of California at San Diego: M.S., Chemistry 2006

University of Toronto: B.S., Chemistry 2002

Articles (5)

Evaluation of iodide chemical ionization mass spectrometry for gas and aerosol-phase per-and polyfluoroalkyl substances (PFAS) analysis

Environmental Science: Processes & Impacts

2023 Per- and polyfluoroalkyl substances (PFAS) are a class of ultra-persistent anthropogenic contaminants. PFAS are ubiquitous in environmental and built systems, but very few online methods exist for their characterization in atmospheric gases and aerosols. Iodide time-of-flight chemical ionization mass spectrometry (iodide-ToF-CIMS) is a promising technology for online characterization of PFAS in the atmosphere. Previous work using iodide-ToF-CIMS was successful in measuring gas-phase perfluoroalkyl carboxylic acids and fluorotelomer alcohols, but those are just two of the myriad classes of PFAS that are atmospherically relevant.

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Nontarget analysis and fluorine atom balances of transformation products from UV/sulfite degradation of perfluoroalkyl contaminants

Environmental Science: Processes & Impacts

2023 Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of highly fluorinated, anthropogenic compounds that are used in a wide variety of consumer applications. Due to their widespread use and high persistence, PFAS are ubiquitous in drinking water, which is of concern due to the threats these compounds pose to human health. Reduction via the hydrated electron is a promising technology for PFAS remediation and has been well-studied. However, since previous work rarely reports fluorine atom balances and often relies on suspect screening, some transformation products are likely unaccounted for.

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A universally applicable method of calculating confidence bands for ice nucleation spectra derived from droplet freezing experiments

Atmospheric Measurement Techniques

2022 A suite of generally applicable statistical methods based on empirical bootstrapping is presented for calculating uncertainty and testing the significance of quantitative differences in temperature and/or ice active site densities between ice nucleation temperature spectra derived from droplet freezing experiments. Such experiments are widely used to determine the heterogeneous ice nucleation properties and ice nucleation particle concentration spectra of different particle samples, as well as in studies of homogeneous freezing. Our methods avoid most of the assumptions and approximations inherent to existing approaches, and when sufficiently large sample sizes are used (approximately >150 droplets and [] bootstrap samples in our system), can capture the full range of random variability and error in ice nucleation spectra.

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Preventing spread of aerosolized infectious particles during medical procedures: A lab-based analysis of an inexpensive plastic enclosure

PLoS One

2022 Severe viral respiratory diseases, such as SARS-CoV-2, are transmitted through aerosol particles produced by coughing, talking, and breathing. Medical procedures including tracheal intubation, extubation, dental work, and any procedure involving close contact with a patient’s airways can increase exposure to infectious aerosol particles. This presents a significant risk for viral exposure of nearby healthcare workers during and following patient care. Previous studies have examined the effectiveness of plastic enclosures for trapping aerosol particles and protecting health-care workers. However, many of these enclosures are expensive or are burdensome for healthcare workers to work with.

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Permafrost landscape history shapes fluvial chemistry, ecosystem carbon balance, and potential trajectories of future change

Global Biogeochemical Cycles

2022 Intensifying permafrost thaw alters carbon cycling by mobilizing large amounts of terrestrial substrate into aquatic ecosystems. Yet, few studies have measured aquatic carbon fluxes and constrained drivers of ecosystem carbon balance across heterogeneous Arctic landscapes. Here, we characterized hydrochemical and landscape controls on fluvial carbon cycling, quantified fluvial carbon fluxes, and estimated fluvial contributions to ecosystem carbon balance across 33 watersheds in four ecoregions in the continuous permafrost zone of the western Canadian Arctic: unglaciated uplands, ice‐rich moraine, and organic‐rich lowlands and till plains.

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