Ryan Sullivan

Associate Professor, Mechanical Engineering, Chemistry

Courtesy Appointment, Civil & Environmental Engineering

Ryan Sullivan

Source: College of Engineering


5000 Forbes Avenue
Doherty Hall 2111
Pittsburgh, PA 15213

Phone: 412-268-8462

Fax: 412-268-3348

Email: rsullivan@cmu.edu

Website: http://www.cmu.edu/particulate-matter/


Dr. Ryan Sullivan is an Associate Professor of Chemistry and Mechanical Engineering at Carnegie Mellon University. He is also a faculty member in the Center for Atmospheric Particle Studies.

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.

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.

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2002 Hon. B.Sc., Chemistry, University of Toronto
2006 M.Sc., Chemistry, University of California, San Diego
2008 Ph.D., Chemistry, University of California, San Diego
2009-2011 Post-Doctoral Fellow and Research Scientist, Colorado State University

Awards and Honors

  • National Science Foundation Faculty Early Career Development Award (CAREER) (2016)
  • Editors’ Citation for Excellence in Refereeing for Geophysical Research Letters (2015)
  • Cozzarelli Prize, National Academy of Science USA (2011)
  • Atmospheric Chemistry Colloquium for Emerging Senior Scientists (ACCESS) X (2009)
  • Department of Chemistry & Biochemistry Teaching Assistant Excellence Award, University of California, San Diego (2004-2005)

Selected Publications

See the complete list of publications here.


  1. Ahern, A. T.; Goldberger, L.; Jahl, L.; Thornton, J.; Sullivan, R. C. Production of N2O5 and ClNO2 through Nocturnal Processing of Biomass-Burning Aerosol. Environ. Sci. Technol. 2018, 52, 550–559, doi:10.1021/acs.est.7b04386.
  2. Ye, Q.; Upshur, M. A.; Robinson, E. S.; Geiger, F. M.; Sullivan, R. C.; Thomson, R. J.; Donahue, N. M. Following Particle-Particle Mixing in Atmospheric Secondary Organic Aerosols by Using Isotopically Labeled Terpenes. Chem 2018, 4, 318–333, doi:10.1016/j.chempr.2017.12.008.
  3. Beydoun, H.; Polen, M.; Sullivan, R. C. A new multicomponent heterogeneous ice nucleation model and its application to Snomax bacterial particles and a Snomax–illite mineral particle mixture. Atmos. Chem. Phys. 2017, 17, 13545–13557, doi:10.5194/acp-17-13545-2017.
  4. Gorkowski, K.; Donahue, N. M.; Sullivan, R. C. Emulsified and Liquid–Liquid Phase-Separated States of α-Pinene Secondary Organic Aerosol Determined Using Aerosol Optical Tweezers. Environ. Sci. Technol. 2017, 51, 12154–12163, doi:10.1021/acs.est.7b03250.
  5. Ahern, A. T.; Subramanian, R.; Saliba, G.; Lipsky, E. M.; Donahue, N. M.; Sullivan, R. C. Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers. Atmos. Meas. Tech. 2016, 9, 6117–6137, doi:10.5194/amt-9-6117-2016.
  6. Beydoun, H.; Polen, M.; Sullivan, R. C. Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra. Atmos. Chem. Phys. 2016, 16, 13359–13378, doi:10.5194/acp-16-13359-2016.
  7. Gorkowski, K.; Beydoun, H.; Aboff, M.; Walker, J. S.; Reid, J. P.; Sullivan, R. C. Advanced aerosol optical tweezers chamber design to facilitate phase-separation and equilibration timescale experiments on complex droplets. Aerosol Sci. Technol. 2016, 50, 1327–1341, doi:10.1080/02786826.2016.1224317.
  8. Polen, M.; Lawlis, E.; Sullivan, R. C. The unstable ice nucleation properties of Snomax® bacterial particles. J. Geophys. Res. Atmos. 2016, 121, 11,666-11,678, doi:10.1002/2016JD025251.
  9. Creamean, J. M.; Suski, K. J.; Rosenfeld, D.; Cazorla, A.; Demott, P. J.; Sullivan, R. C.; White, A. B.; Ralph, F. M.; Minnis, P.; Comstock, J. M.; Tomlinson, J. M.; Prather, K. A.Dust and biological aerosols from the Sahara and Asia influence precipitation in the Western U.S.Science, 339, 1572–1578, 2013.
  10. Sullivan, R.C., Miñambres, L., DeMott, P.J., Prenni, A.J., Carrico, C.M., Levin, E., Kreidenweis, S.M.,Chemical processing does not always impair heterogeneous ice nucleation properties of mineral dust particlesGeophysical Research Letters, 37, L24805, doi:10.1029/2010GL045540, 2010.
  11. Sullivan, R. C.; Moore, M. J. K.; Petters, M. D.; Kreidenweis, S. M.; Roberts, G. C.; Prather, K. A. Timescale for hygroscopic conversion of calcite mineral particles through heterogeneous reaction with nitric acid. Phys. Chem. Chem. Phys. 2009, 11, 7826, doi:10.1039/b904217b.
  12. Sullivan, R.C., Moore, M.J.K., Petters, M.D., Kreidenweis, S.M., Roberts, G.C., Prather, K.A. Effect of chemical mixing state on the hygroscopicity and cloud nucleation properties of calcium mineral dust particles, Atmospheric Chemistry and Physics, 9, 3303-3316, 2009.
  13. Sullivan, R.C., Guazzotti, S.A., Sodeman, D.A., Prather, K.A. Direct observations of the atmospheric processing of Asian mineral dust. Atmospheric Chemistry and Physics, 7, 1213-1226, 2007.