Hildebrandt Ruiz, Lea, Ph.D.

Assistant Professor Headshot of Professor Lea Hildebrandt Ruiz

CPE 3.470
PRC Bldg. 133, 1.320E
Mailing Address:
Phone: (512) 471-1050 The University of Texas at Austin
Fax: (512) 471-7060 McKetta Department of Chemical Engineering
Email: lhr@che.utexas.edu 200 E Dean Keeton St.
UT Mail: C0400 Austin, TX 78712-1589

Research Areas: Environmental Engineering

Research Group Website

Research Presentation for Prospective Graduate Students

Educational Qualifications

NSF Postdoctoral Fellow, National Center for Atmospheric Research (2011-2012)
Ph.D., Chemical Engineering and Engineering & Public Policy, Carnegie Mellon University (2011)
B.S., Chemical Engineering, California Institute of Technology (2006)


Air quality, atmospheric chemistry, nanoparticles, mass spectrometry, environmental sustainability


Air pollution kills – about 50,000 people per year in the United States alone. Our research focuses on how gas and particle-phase pollutants form and transform in the atmosphere. Research tools include laboratory experiments using a state-of-the-art environmental chamber facility, ambient measurements, and mathematical modeling. Laboratory experiments and ambient measurements use highly advanced mass spectrometric techniques including a High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) coupled to a particle collector, and an aerosol chemical speciation monitor (ACSM). The ultimate goal of this research is to make better-informed recommendations for environmental policies aimed at improving air quality and human health.

Courses Taught

CHE 348 Numerical Methods in Chemical Engineering and Problem Solving
CHE 379/384 Atmospheric Physicochemical Processes

Awards & Honors

Education Committee, American Association for Aerosol Research (2014-current)
Programming Chair, American Association for Aerosol Research (2013-2014)
NSF Postdoctoral Research Fellowship (2011 – 2012)
EPA Graduate Research Fellowship (2010 – 2011)
NSF Graduate Research Fellowship (2006 – 2009)

Selected Publications

  • Paciga, E. Karnezi, E. Kostenidou, L. Hildebrandt, M. Psichoudaki, G. J. Engelhart, B. H. Lee, M. Crippa, A. S. H. Prevot, U. Baltensperger, and S. N. Pandis. Volatility of organic aerosol and its components in the Megacity of Paris. Atmospheric Chemistry and Physics Discussions, 15, 22263 – 22289, 2015.
  • K. Bean and L. Hildebrandt Ruiz. Hydrolysis and Gas-particle Partitioning of Organic Nitrates Formed from the Oxidation of α-Pinene in Environmental Chamber Experiments. Atmospheric Chemistry and Physics Discussions, 15, 20629 – 20653, 2015.
  • Pikridas, J. Sciare, F. Freutel, S. Crumeyrolle, S.-L. von der Weiden-Reinmüller, A. Borbon, A. Schwarzenboeck, M. Merkel, M. Crippa, E. Kostenidou, M. Psichoudaki, L. Hildebrandt, G. J. Engelhart, T. Petäjä, A. S. H. Prévôt, F. Drewnick, U. Baltensperger, A. Wiedensohler, M. Kulmala, M. Beekmann, and S. N. Pandis. Ultrafine particle sources and in-situ formation in a European Megacity. Atmospheric Chemistry and Physics, in press, 2015.
  • Hildebrandt Ruiz, A.L. Paciga, K. Cerully, A. Nenes, N.M. Donahue and S.N. Pandis. Formation and Aging of Secondary Organic Aerosol from Toluene: Changes in Chemical Composition, Volatility and Hygroscopicity, Atmospheric Chemistry and Physics, 15, 8301-8313, 2015.
  • Zhao, S. Wang, N. M. Donahue, W. Chuang, L. Hildebrandt Ruiz, N. L. Ng, Y. Wang, J. Hao. Evaluation of one-dimensional and two-dimensional volatility basis sets in simulating the aging of secondary organic aerosol with smog chamber experiments, Environmental Science and Technology, 49 (4), 2245-2254, 2015.
  • R. Canagaratna, J. L. Jimenez, J. H. Kroll, Q. Chen, S. H. Kessler, P. Massoli, L. Hildebrandt Ruiz, E. Fortner, L. R. Williams, K. R. Wilson, J. D. Surratt, N. M. Donahue, J. T. Jayne, and D. R. Worsnop. Elemental Ratio Measurements of Organic Compounds using Aerosol Mass Spectrometry: Characterization, Improved Calibration, and Implications. Atmospheric Chemistry and Physics 15, 253-272, 2015.
  • M. Crippa, F. Canonaco, V. A. Lanz, M. Äijälä, J. D. Allan, S. Carbone, G, Capes, M. Dall’Osto, D. A. Day, P. F. DeCarlo, M. Ehn, A. Eriksson, E. Freney, L. Hildebrandt Ruiz, R. Hillamo, J.-L. Jimenez, H. Junninen, A. Kiendler-Scharr, A.-M. Kortelainen, M. Kulmala, A. A. Mensah, C. Mohr, E. Nemitz, C. O’Dowd, J. Ovadnevaite, S. N. Pandis, T. Petäjä, L. Poulain, S. Saarikoski, K. Sellegri, E. Swietlicki, P. Tiitta, D. R. Worsnop, U. Baltensperger, A. S. H. Prévôt. Compilation of organic aerosol components for 25 AMS datasets across Europe using a newly developed ME-2 based source apportionment strategy. Atmospheric Chemistry and Physics, 14, 6159–6176, 2014.
  • T. Yli-Juuti, K. Barsanti, L. Hildebrandt Ruiz, A.-J. Kieloaho, U. Makkonen, T. Petäjä, M. Kulmala and I. Riipinen. Model for acid-base chemistry in nanoparticle growth. Atmospheric Chemistry and Physics, 13, 12507 – 12524, 2013
  • M. R. Pennington, B. R. Bzdek, J. W. DePalma, J. N. Smith, A.-M. Kortelainen, L. Hildebrandt Ruiz, T. Petäjä, M. Kulmala, D. R. Worsnop, M. V. Johnston. Identification and quantification of particle growth channels during new particle formation. Atmospheric Chemistry and Physics, 13, 10215-10225, 2013.
  • M. Pikridas, I. Riipinen, L. Hildebrandt, E. Kostenidou, H. Manninen, N. Mihalopoulos, N. Kalivitis, J. Burkhart, A. Stohl, M. Kulmala, S. N. Pandis. New particle formation at a remote marine site in the Eastern Mediterranean. Journal of Geophysical Research – Atmospheres, 117, D12205, doi:10.1029/2012JD017570, 2012.
  • L. Hildebrandt, E. Kostenidou, V. A. Lanz, G. Kouvarakis, A. S. H. Prevot, U. Baltensperger, N. Mihalopoulos, N.M. Donahue and S.N. Pandis. Sources and Atmospheric Processing of Organic Aerosol in the Mediterranean: Insights from Aerosol Mass Spectrometer Factor Analysis. Atmospheric Chemistry and Physics, 11, 12499–12515, 2011.
  • L. Hildebrandt, K. Henry, J.H. Kroll, D. R. Worsnop, S.N. Pandis and N.M. Donahue. Evaluating the Mixing of Organic Aerosol Components Using High-Resolution Aerosol Mass Spectrometry. Environmental Science and Technology 45, 6329-6335, 2011.
  • G.J. Engelhart, L. Hildebrandt, E. Kostenidou, N. Mihalopoulos, N.M. Donahue, S.N. Pandis. Water content of aged aerosol. Atmospheric Chemistry and Physics 11, 911-920, 2011.
  • B.-H. Lee, E. Kostenidou, L. Hildebrandt, I. Riipinen, G.J. Engelhart, C. Mohr, P.F. DeCarlo, N. Mihalopoulos, A.S.H. Prevot, U. Baltensperger, S.N. Pandis. Measurement of the Ambient Organic Aerosol Volatility Distributions: Application during the Finokalia Aerosol Measurement Experiment (FAME-2008). Atmospheric Chemistry and Physics 10, 12149-12160, 2010.
  • L. Hildebrandt, E. Kostenidou, D. R. Worsnop, N. Mihalopoulos, N.M. Donahue and S.N. Pandis. Formation of Highly Oxygenated Organic Aerosol in the Atmosphere: Insights from the Finokalia Aerosol Measurement Experiments. Geophysical Research Letters 37, L23801, doi:10.1029/2010GL045193, 2010.
  • M. Pikridas, K. Bougiatioti, L. Hildebrandt, G.J. Engelhart, E. Kostenidou, C. Mohr, A. S. H. Prevot, G. Kouvarakis, P. Zarmpas, J. F. Burkhart, B.-H. Lee, M. Psichoudaki, N. Mihalopoulos, C. Pilinis, A. Stohl, U. Baltensperger, M. Kulmala, and S. N. Pandis: The Finokalia Aerosol Measurement Experiments – 2008 (FAME-08): An Overview, Atmospheric Chemistry and Physics 10, 6793–6806, 2010.
  • N. L. Ng, M. R. Canagaratna, Q. Zhang, J. L. Jimenez, J. Tian, I. M. Ulbrich, J. H. Kroll, K. S. Docherty, P. S. Chhabra, R. Bahreini, S. M. Murphy, J. H. Seinfeld, L. Hildebrandt, N. M. Donahue, P. F. DeCarlo, V. A. Lanz, A. S. H. Prevot, E. Dinar, Y. Rudich, and D. R. Worsnop: Organic aerosol components observed in northern hemispheric datasets from aerosol mass spectrometry, Atmospheric Chemistry and Physics 10, 4625-4641, 2010.
  • L. Hildebrandt, G.J. Engelhart, , C. Mohr, E. Kostenidou, V. A. Lanz, A. Bougiatioti, P. F. DeCarlo, A. S. H. Prevot, U. Baltensperger, , N. Mihalopoulos, N.M. Donahue and S.N. Pandis. Aged organic aerosol in the Eastern Mediterranean: The Finokalia Aerosol Measurement Experiment – 2008, Atmospheric Chemistry and Physics 10, 4167-4186, 2010.
  • L. Hildebrandt, N.M. Donahue and S.N. Pandis. High formation of secondary organic aerosol from the photo-oxidation of toluene. Atmospheric Chemistry and Physics 9, 2973–2986, 2009.
  • J.R. Pierce, G.J. Engelhart, L. Hildebrandt, E.A. Weitkamp, R.K. Pathak, N.M. Donahue, A.L. Robinson, P.J. Adams and S.N. Pandis. Constraining particle evolution from wall losses, coagulation, and condensation-evaporation in smog-chamber experiments: Optimal estimation based on size distribution measurements. Aerosol Science and Technology 42, 1001-1015, 2008.
  • U. Dusek, G.P. Frank, L. Hildebrandt, J. Curtius, J. Schneider, S. Walter, D. Chand, F. Drewnick, S. Hings, D. Jung, S. Borrmann, M.O. Andreae. Size matters more than chemistry for cloud-nucleating ability of aerosol particles. Science 312, 1375-1378, 2006.
  • M.I. Guzman, L. Hildebrandt, A.J. Colussi, M.R. Hoffmann. Cooperative hydration of pyruvic acid in ice. Journal of the American Chemical Society 128, 10621-10624, 2006.
  • J.D. Surratt, S.M. Murphy, J.H. Kroll, N.L. Ng, L. Hildebrandt, A. Sorooshian, R. Szmigielski, R. Vermeylen. W. Maenhaut, M. Claeys, R.C. Flagan, J.H. Seinfeld. Chemical composition of secondary organic aerosol formed from the photooxidation of isoprene. Journal of Physical Chemistry A 110, 9665-9690, 2006.