In 1992, Professor Prather completed her postdoctoral fellowship with Prof. Yuan T. Lee and started as an Asst. Professor at UC Riverside. It was at UC Riverside that Prof. Prather invented and patented the first ATOFMS (aka "The Beast") (Prather, 1994). In early studies, the Prather group developed ATOFMS source libraries which were first used to characterize the sources of aerosols in California air pollution. With funding from the California Air Resources Board (CARB), transportable ATOFMS instruments (Jake and Elwood) were developed and used for determining the sources of atmospheric aerosols in real-time. The Prather group demonstrated that these laser-based instruments could indeed be transported to the other side of the globe and successfully used to provide insights into the atmospheric sources of pollution worldwide (Ramanathan 2001).
In 2001, Prof. Prather moved to UC San Diego with a joint appointment in the Dept. of Chemistry and Biochemistry and Scripps Institution of Oceanography. After moving, her research shifted from instrument development to the use of these instruments in probing the impacts of aerosols on human health and climate. The impact of aerosols on clouds and climate represents the single largest uncertainty in our overall understanding of climate change. Prather group research focuses on the area that presents the largest challenge, understanding how complex chemical processes and different aerosol sources impact clouds and climate.
ATOFMS has proven to be capable of differentiating between emissions from cars, trucks, ship, incineration, coal burning, wildfires, dust, and biological particles (e.g., Toner 2006; Ault 2009). The 3rd generation ATOFMS instrument (aka Laverne), based on the design of Jake and Elwood, was modified to become more compact, and was commercialized by TSI, Inc.. ATOFMS is now being used in studies worldwide, with a significant effort currently being undertaken in Asia. In 2009, the 4th generation of the instrument, named Shirley, was developed with the compact design that is necessary for airborne research (Pratt 2009a). Shirley first flew on the NSF/NCAR C-130 out of Colorado, detecting bioparticles in ice residues within mixed phase clouds (Pratt, 2009b) and obtaining unique information on the vertical profile dependence of the chemical composition of atmospheric aerosols (Pratt 2010).
In 2010, Prof. Prather became the Distinguished Chair in Atmospheric Chemistry. She was also elected as a Fellow of the prestigious American Academy of Arts and Sciences, of the American Association for the Advancement of Sciences, and of the American Geophysical Union.
In 2010, Prof. Prather spearheaded an effort to develop a plan for bringing the real world into the lab in an effort to perform the needed studies to bridge the gap between lab and field measurements. She assembled a proposal team that wrote a successful Phase I proposal, and ultimately succeeded in accurately generating sea spray aerosols using real seawater, complex biology, and the proper production mechanism. As a result of the success of Phase I, in 2013 the National Science Foundation Center selected the Center for Aerosol Impacts on Climate and the Environment to become a $20 million Phase II Center which Prof. Prather now directs alongside Profs. Vicki Grassian (U. of Iowa) and Tim Bertram (U. of Wisconsin, Madison) who serve as co-Director and Associate Director, respectively. In an effort to better understand how aerosols impacted climate before humans exerted a major influence, the Center is initially focusing on determining how sea spray from the ocean impacts clouds and climate. Ultimately, a smog chamber will be added to the simulated ocean-atmosphere environment to allow CAICE scientists to increase the complexity of the system by adding in human-made pollution. This will allow CAICE scientists to study interactions between natural and anthropogenic atmospheric constiutents in a controlled system. CAICE studies are branching out to integrate many techniques in an effort to better understand complex chemical processing at the individual particle level. These techniques include 2-step laser desorption/ionization and high resolution mass spectrometry, IR and Raman spectroscopy, optical microscopy, and atomic force microscopy.
Examples of our major findings over the past two decades:
- In the very first field study conducted in 1996 with the ATOFMS, in collaboration with Glen Cass's group, the Prather group directly measured heterogeneous reactions occurring on individual sea spray particles for the first time (Gard 1998).
- ATOFMS was used to demonstrate that chemically distinct types of particles exist which include aged and fresh forms of fossil fuel soot, biomass burning, organic aerosols, sea spray, and dust which show a strong size-composition dependence (Noble 1996). The relative proportions of different particle types have since been shown by many other groups to dominate atmospheric aerosols worldwide, with their relative fractions determined by proximity to the sources and degree of atmospheric processing (Hughes, 2000).
- In the Indian Ocean Experiment, performed in 1999, the Prather group showed that air pollution due to biomass burning dominates over that due to fossil fuel combustion in India (Guazzotti 2003).
- The Prather group was the first to report the episodic high abundance of amine salts in atmospheric aerosols. These early results were initially scrutinized due to the volatility of amines. The group suggested amines could be undergoing acid-base chemistry, which has since been proven to be critical to particle formation and growth processes (Angelino 2001)-- a current area of intense focus in atmospheric chemistry studies.
- During ACE-Asia-2001, the Prather group showed that mineralogy strongly affects the heterogeneous reactivity of individual Asian dust particles (Sullivan 2007).
- During MILAGRO, the Prather group detected high amounts of biomass burning in Mexico City, a source which was not prevalent in previous Mexico City studies by other groups. Since then, biomass burning and incineration have indeed been shown to be major components in Mexico City as well as many developing countries around the world (Moffet 2008a; 2008b).
- During MILAGRO and SOAR-2007, the Prather group used optical signals from ATOFMS to directly determine optical properties as a function of mixing state of atmospheric aerosols in Mexico City and Riverside (Moffet 2008c). The group showed that aged soot absorbs and heats the atmosphere ~3 times more than freshly emitted soot, matching modeling work done by Jacobson (Moffet 2009).
- In CalWater (2009-2011), the Prather group showed that dust and bioparticles transported from as far away as Africa impact precipitation processes over the California Sierra Nevadas (Ault 2009; Creamean 2013). This has motivated novel efforts to add dust aerosols to weather forecasting models.
- As part of CAICE, the Prather group developed a simulated ocean-atmosphere environment using a wave flume filled with real seawater, successfully transferring the complexity of sea spray aerosol into a laboratory setting for controlled studies of reactivity and climate properties (Prather 2013).
- 2013: The Prather group performed mesocosm experiments inducing phytoplankton, bacteria, and viruses to grow, interact, and transform seawater composition leading to correlated changes in the reactivity and climate properties of sea spray. These represent the most chemically complex lab-based studies of aerosols to date. They will provide critical explanations for atmospheric field observations and will be used to improve climate models.
- In addition to atmospheric studies, the ATOFMS has been used as a versatile on-line mass spectrometry tool in a broad range of fields including MALDI of single cells, biowarfare detection, cancer cell analysis, metal organic framework and materials characterization, and pharmaceutrial powders and inhalants.
Prather, K. A., T. Nordmeyer and K. Salt (1994). "Real-Time Characterization of Individual Aerosol-Particles Using Time-of-Flight Mass-Spectrometry." Analytical Chemistry 66(9): 1403-1407.(cited 289 times)
Noble, C. A. and K. A. Prather (1996). "Real-time measurement of correlated size and composition profiles of individual atmospheric aerosol particles." Environmental Science & Technology 30(9): 2667-2680. (cited 239 times)
Gard, E., J. E. Mayer, B. D. Morrical, T. Dienes, D. P. Fergenson and K. A. Prather (1997). "Real-time analysis of individual atmospheric aerosol particles: Design and performance of a portable ATOFMS."Analytical Chemistry 69(20): 4083-4091. (cited 397 times)
Gard, E. E., M. J. Kleeman, D. S. Gross, L. S. Hughes, J. O. Allen, B. D. Morrical, D. P. Fergenson, T. Dienes, M. E. Galli, R. J. Johnson, G. R. Cass and K. A. Prather (1998). "Direct observation of heterogeneous chemistry in the atmosphere." Science 279(5354): 1184-1187. (cited 224 times)
Hughes, L. S., J. O. Allen, P. Bhave, M. J. Kleeman, G. R. Cass, D. Y. Liu, D. F. Fergenson, B. D. Morrical and K. A. Prather (2000). "Evolution of atmospheric particles along trajectories crossing the Los Angeles basin." Environmental Science & Technology 34(15): 3058-3068. (cited 94 times)
Ramanathan, V., P. J. Crutzen, et al. (2001). "Indian Ocean Experiment: An integrated analysis of the climate forcing and effects of the great Indo-Asian haze." Journal of Geophysical Research-Atmospheres 106(D22): 28371-28398. (cited 618 times)
Guazzotti, S. A., D. T. Suess, K. R. Coffee, P. K. Quinn, T. S. Bates, A. Wisthaler, A. Hansel, W. P. Ball, R. R. Dickerson, C. Neususs, P. J. Crutzen and K. A. Prather (2003). "Characterization of carbonaceous aerosols outflow from India and Arabia: Biomass/biofuel burning and fossil fuel combustion." Journal of Geophysical Research-Atmospheres 108(D15). (cited 63 times)
Angelino, S., D. T. Suess and K. A. Prather (2001). "Formation of aerosol particles from reactions of secondary and tertiary alkylamines: Characterization by aerosol time-of-flight mass spectrometry." Environmental Science & Technology 35(15): 3130-3138. (cited 125 times)
Sullivan, R. C. and K. A. Prather (2005). "Recent advances in our understanding of atmospheric chemistry and climate made possible by on-line aerosol analysis instrumentation." Analytical Chemistry77(12): 3861-3885. (cited 118 times)
Pratt, K. A. and K. A. Prather (2012). "Mass spectrometry of atmospheric aerosols: Recent developments and applications. Part II: On-line mass spectrometry techniques." Mass Spectrometry Reviews31(1): 17-48. (cited 37 times)
Ault, A. P., M. J. Moore, H. Furutani and K. A. Prather (2009). "Impact of Emissions from the Los Angeles Port Region on San Diego Air Quality during Regional Transport Events."Environmental Science & Technology 43(10): 3500-3506. (cited 32 times)
Sullivan, R. C., S. A. Guazzotti, D. A. Sodeman and K. A. Prather (2007). "Direct observations of the atmospheric processing of Asian mineral dust." Atmospheric Chemistry and Physics 7: 1213-1236. (cited 165 times)
Moffet, R. C., B. de Foy, L. T. Molina, M. J. Molina and K. A. Prather (2008a). "Measurement of ambient aerosols in northern Mexico City by single particle mass spectrometry." Atmospheric Chemistry and Physics 8(16): 4499-4516. (cited 99 times)
Moffet, R. C. et al. (2008b). "Characterization of aerosols containing Zn, Pb, and Cl from an industrial region of Mexico City." Environ. Science & Technology 42(19): 7091-7097. (cited 62 times)
Moffet, R. C., X. Y. Qin, T. Rebotier, H. Furutani and K. A. Prather (2008c). "Chemically segregated optical and microphysical properties of ambient aerosols measured in a single-particle mass spectrometer." Journal of Geophysical Research-Atmospheres 113(D12). (cited 25 times)
Moffet, R. C. and K. A. Prather (2009). "In-situ measurements of the mixing state and optical properties of soot with implications for radiative forcing estimates." Proceedings of the National Academy of Sciences of the United States of America 106(29): 11872-11877. (cited 105 times)
Pratt, K. A., J. E. Mayer, J. C. Holecek, R. C. Moffet, R. O. Sanchez, T. P. Rebotier, H. Furutani, M. Gonin, K. Fuhrer, Y. X. Su, S. Guazzotti and K. A. Prather (2009a). "Development and Characterization of an Aircraft Aerosol Time-of-Flight Mass Spectrometer." Analytical Chemistry 81(5): 1792-1800. (cited 40 times)
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 (2009b). "In situ detection of biological particles in cloud ice-crystals." Nature Geoscience 2(6): 397-400. (cited 140 times)
Pratt, K. A. and K. A. Prather (2010). "Aircraft measurements of vertical profiles of aerosol mixing states." Journal of Geophysical Research-Atmospheres 115.
Ault, A. P., C. R. Williams, A. B. White, P. J. Neiman, J. M. Creamean, C. J. Gaston, F. M. Ralph and K. A. Prather (2011). "Detection of Asian dust in California orographic precipitation." Journal of Geophysical Research-Atmospheres 116.
Creamean, J. M., K. J. Suski, D. Rosenfeld, A. Cazorla, P. J. DeMott, R. C. Sullivan, A. B. White, F. M. Ralph, P. Minnis, J. M. Comstock, J. M. Tomlinson and K. A. Prather (2013). "Dust and Biological Aerosols from the Sahara and Asia Influence Precipitation in the Western U.S." Science 339(6127): 1572-1578.
Prather, K. A., T. H. Bertram, V. H. Grassian, G. B. Deane, M. D. Stokes, P. J. DeMott, L. I. Aluwihare, B. P. Palenik, F. Azam, J. H. Seinfeld, R. C. Moffet, M. J. Molina, C. D. Cappa, F. M. Geiger, G. C. Roberts, L. M. Russell, A. P. Ault, J. Baltrusaitis, D. B. Collins, C. E. Corrigan, L. A. Cuadra-Rodriguez, C. J. Ebben, S. D. Forestieri, T. L. Guasco, S. P. Hersey, M. J. Kim, W. F. Lambert, R. L. Modini, W. Mui, B. E. Pedler, M. J. Ruppel, O. S. Ryder, N. G. Schoepp, R. C. Sullivan and D. F. Zhao (2013). "Bringing the ocean into the laboratory to probe the chemical complexity of sea spray aerosol."Proceedings of the National Academy of Sciences of the United States of America 110(19): 7550-7555.
9018 Citations and H-index = 52
**Number of citations taken from Google Scholar as of February 23, 2014