Ryan Sullivan
Professor, Chemistry, Mechanical Engineering
Courtesy Appointment, Civil and Environmental Engineering
Associate Director, Institute for Green Science
Bio
Ryan Sullivan is a professor of Chemistry and Mechanical Engineering at Carnegie Mellon University. He is also a faculty member in the Centre for Atmospheric Particle Studies. 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.
Education
- Ph.D., Chemistry, University of California, San Diego, 2008
- MS, Chemistry, University of California, San Diego, 2006
- BS, Chemistry, University of Toronto, 2002
Research
Particles in the atmosphere exist in a wide variety of shapes, sizes, and chemical compositions. These properties are highly dynamic, constantly evolving as the particles respond to changes in their gas-phase environment. This makes the study of atmospheric aerosol particles both challenging and fascinating. The important but still poorly understood roles that particles play in influencing air quality, the atmosphere’s chemical balance, cloud nucleation, energy balance, biogeochemical cycles, and other important climate feedbacks motivate our interest in improving our understanding of the chemical behavior of particles in our atmosphere. Our comprehension of these processes is currently limited by the instrumentation available to measure key properties of individual atmospheric particles.
We investigate these important physicochemical particle properties using custom single-particle instruments that allow us to rapidly characterize atmospheric aerosols in real-time, one particle after another. We are developing improved analytical methods to measure individual particles using laser ablation mass spectrometry, and laser spectroscopy. These new instruments are utilized in both laboratory studies and field experiments (from ground, ship, and aircraft sampling platforms) to determine the kinetics and products of a variety of atmospheric chemical aging processes (e.g. heterogeneous reaction, aqueous-phase chemistry, gas-to-particle conversion, photochemistry, new particle formation). Small cloud simulation chambers are also used to determine the ability of the chemically processed particles to nucleate both warm cloud droplets, and ice crystals via heterogeneous ice nucleation.
Single-particle analysis is an important analytical tool that allows us to determine how the myriad chemical constituents are distributed between individual particles (mixing state). As all particle properties (interaction with radiation, heterogeneous kinetics, hygroscopicity, heterogeneous ice nucleation, toxicity, etc.) are dictated by each particle’s unique size and chemical composition, single-particle analysis is required to determine the exact relationships between the sources of atmospheric particles, their size and chemical composition, how they behave chemically in the atmosphere, and what their resulting important environmental effects are.
Sullivan explains his research in using UV light to blast apart PFAS molecules.
Sullivan discusses his group's work using aerosol optical tweezers to study atmospheric particles that impact both human health and global climate change.
By understanding the properties of individual water particles in the clouds, explains Sullivan, we can better predict the onset of severe storms, floods, and droughts—and even human-influenced climate change.