Kerri Pratt

Atmospheric chemistry impacts global climate, regional air pollution, and human health. Air-surface interactions are important components of global atmospheric and biogeochemical cycles. Chemical reactions occur in the environment between trace gases, within aqueous solutions (e.g. cloud droplets), within particles, and on surfaces (e.g. snow, ice, atmospheric particles, vegetation). Atmospheric particles, often ~3 nm to 10 microns in diameter, are constantly evolving, complex mixtures that interact with radiation, form cloud droplet and ice crystals, and deposit onto surfaces. Primary atmospheric particles are emitted from a variety of natural and anthropogenic sources (e.g., dust, bacteria, sea spray, soot) and undergo heterogeneous and particle-phase reactions during transport. Secondary organic aerosol, formed primarily from the oxidation of trace level volatile organic compounds and subsequent gas-particle partitioning, is a dynamic chemical mixture, wherein each particle can contain thousands of organic compounds, the vast majority of which remain unidentified. Given the complexity and evolving nature of atmospheric particles, their measurement represents an analytical challenge and has resulted in significant uncertainties in our understanding of particle formation, evolution, and environmental impacts and fate.

The Pratt group focuses on studies of interactions between atmospheric trace gases, particles, and clouds using novel mass spectrometry techniques. In particular, we tackle the major uncertainties that exist in our understanding of atmospheric composition in the Polar Regions, especially in the Arctic, which is experiencing rapid sea ice loss and increasing shipping and development. We use a custom-built, field-portable single-particle mass spectrometer to measure the size and chemistry of individual particles in real-time. Trace gas composition is measured using a field-portable on-line chemical ionization mass spectrometer. To study the molecular composition of high molecular weight organics, electrospray ionization coupled with high-resolution mass spectrometry is used to probe ambient samples. These measurements of trace gases, aerosols, and cloud water are complemented by one-dimensional modeling predict atmospheric composition versus altitude and time. These studies will improve our understanding of the feedbacks between natural aerosol sources, anthropogenic emissions, and the Earth system for future climate and air quality predictions.

Representative Publications

Raso, A.R.W., K.D. Custard, N.W. May, D.J. Tanner, K. Newburn, L. Walker, R. Moore, L.G. Huey, M.L. Alexander, P.B. Shepson, and K.A. Pratt*. 2017. Active molecular iodine photochemistry in the Arctic. Proceedings of the National Academy of Sciences of the United States of America, doi:10.1073/pnas.1702803114.

Gunsch, M.J., R.M. Kirpes, K.R. Kolesar, T.E. Barrett, S. China, R.J. Sheesley, A. Laskin, A. Wiedensohler, T. Tuch, and K.A. Pratt*. 2017. Contributions of transported Prudhoe Bay oilfield emissions to the aerosol population in UtqiaÄ¡vik, Alaska. Atmospheric Chemistry & Physics, doi:10.5194/acp-2017-453.

Peterson, P.K., H. Sihler, D. Pöhler, J. Zielcke, S. General, U. Frieß, U. Platt, W.R. Simpson, S.V. Nghiem, P.B. Shepson, B.H. Stirm, S. Dhaniyala, T. Wagner, D.R. Caulton, J.D. Fuentes and K.A. Pratt*. 2017. Observations of bromine monoxide transport in the Arctic sustained on aerosol particles. Atmospheric Chemistry & Physics, 17: 7567-7579.

Custard, K.D., A.R.W. Raso, P.B. Shepson, R.M. Staebler and K.A. Pratt*. 2017. Production and release of molecular bromine and chlorine from the Arctic coastal snowpack. ACS Earth and Space Chemistry, 1: 142-151.

Boone, E.J., A. Laskin, J. Laskin, C. Wirth, P.B. Shepson, B.H. Stirm and K.A. Pratt*. 2015. Aqueous processing of atmospheric organic particles in cloud water collected via aircraft sampling. Environmental Science & Technology, 49: 8523-8530.

Pratt, K.A.*, K. D. Custard, P.B. Shepson, T.A. Douglas, D. Pohler, S. General, J. Zielcke, W.R. Simpson, U. Platt, D.J. Tanner, L.G. Huey, M. Carlsen and B.H. Stirm. 2013. Photochemical production of molecular bromine in Arctic surface snowpacks. Nature Geoscience. 6: 351-356.

Pratt, K.A., P.J. DeMott*, J.R. French, Z. Wang, D.L. Westphal, A.J. Heymsfield, C.H. Twohy, A.J. Prenni and K.A. Prather*. 2009. In-situ detection of biological particles in cloud ice crystals. Nature Geoscience. 2: 398-401.

Pratt, K.A., J.E. Mayer, J.C. Holecek, R.C. Moffet, R.O. Sanchez, T. Rebotier, H. Furutani, M. Gonin, K. Fuhrer, Y. Su, S. Guazzotti and K.A. Prather*. 2009. Development and characterization of an aircraft aerosol time-of-flight mass spectrometer. Analytical Chemistry. 81: 1792-1800.

Awards

ACS James J. Morgan ES&T Early Career Award, 2018

Eastern Analytical Symposium Young Investigator Award, 2018

Sloan Research Fellowship in Chemistry, 2017

College of Literature, Science, and the Arts Individual Award for Outstanding Contributions to Undergraduate Education, 2017

National Academy of Sciences Gulf Research Program Early Career Fellowship, 2016

Department of Chemistry Seyhan N. Ege Junior Faculty Award, 2016

American Society for Mass Spectrometry Research Award, 2014
Society for Analytical Chemists of Pittsburgh Starter Grant Award, 2014
NSF Postdoctoral Fellowship in Polar Regions Research, 2011
NOAA Climate & Global Change Postdoctoral Fellowship, 2009
NSF Graduate Research Fellowship, 2006

EPA STAR Graduate Fellowship, 2005

Research Areas(s)

• Analytical Chemistry
• Environmental Chemistry

Field(s) of Study

• Mass spectrometry
• Atmospheric trace gases and particles
• Cloud and snow chemistry
• Cryosphere-atmosphere interactions
• Biosphere-atmosphere interactions