Richard Flagan

flagan The Pursuit of the Ideal Aerosol Measurement

About the Presenter:

Professor Flagan focuses on aerosols, and includes studies of secondary organic aerosols in the atmosphere, of biological particles such as pollen and their health impacts, and of the formation of particles and clouds in the atmosphere of Titan. At the center of his work is the development of methods for the physical, chemical, and biochemical characterization of aerosol particles ranging from particles as small a 1 nm diameter to pollen grains that can exceed 100 μm in size. He also applies methods derived from aerosol science to the study of phase transitions in materials, and the development of separations technologies.

Full Presentation:


Aerosol science has advanced in fits and starts, with advances in instrumentation and experimental methods driving many of the advances. Early measurements probed the physical nature of the aerosol, and the dynamic processes leading to those properties. The focus of aerosol measurements has increasingly shifted from fundamental aerosol physics to the effects of aerosols on human health, climate, ecosystems, and the technologies in which they arise. With this shift, the nature of the ideal measurement has changed as well. The primary measurement being made to assess exposure to particulate pollution and its impacts on human health is PM2.5, but a growing body of evidence shows that a tiny mass of ultrafine particles can have profound health effects. Half the particles in the global atmosphere result from nucleation of vapor-phase precursors, impacting radiative forcing of climate after they have grown large enough to efficiently scatter sunlight or to act as cloud condensation nuclei. In aerosol technology, nucleation processes are central to the synthesis of engineered nanoparticles and structures. Though the same particles are involved in the first two arenas, and the same size range and physical mechanisms in all three, very different methods will be required to address the underlying science. Similarly, optical measurements of larger particles are central to our understanding of radiative forcing, and to the characterization of the aerosol burden on the global scale through remote sensing. The continued advance of aerosol science requires ongoing pursuit of improved measurement technology, but the directions for these improvements for different applications may diverge.