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Photo of Hildebrandt Ruiz, Lea
Office Location: CPE 5.458, EME 1.320E

Lea Hildebrandt Ruiz

Associate Professor

Chevron Centennial Teaching Fellowship in Chemical Engineering

Department 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, energy, environmental sustainability


Air pollution kills – worldwide more than 7 million people per year. In order to reduce concentrations of air pollutants their formation, transformation and atmospheric fate need to be understood. This is the focus of our work. Our research tools include state-of-the-science instrumentation used in laboratory experiments and field measurements in indoor and outdoor environments, as well as mathematical modeling. The main goal of our research is to make better-informed recommendations for environmental policies aimed at improving air quality and human health. 

Courses Taught

CHE 317 Introduction to Chemical Engineering Analysis
CHE 348 Numerical Methods in Chemical Engineering and Problem Solving
CHE 379/384 Atmospheric Chemistry and Physics

Awards & Honors

James J. Morgan Early Career Award, American Chemical Society (2021)

Early Career Award, American Institute of Chemical Engineers, Environmental Division (2020)

Elected to Board of Directors, American Association for Aerosol Research (2018)

CAREER Award, U.S. National Science Foundation (2017 – 2022)

NSF Postdoctoral Research Fellowship (2011 – 2012)

EPA Graduate Research Fellowship (2010 – 2011)

NSF Graduate Research Fellowship (2006 – 2009)

Selected Publications

  • Catherine Masoud, and Lea Hildebrandt Ruiz*. Chlorine-initiated oxidation of α-pinene: Formation of secondary organic aerosol and highly oxygenated organic molecules. ACS Earth and Space Chemistry, 5, 9, 2307–2319, 2021.
  • Leif G. Jahn, Dongyu S. Wang, Surya Venkatesh Dhulipala, and Lea Hildebrandt Ruiz*. Gas-phase chlorine radical oxidation of alkanes: effects of structural branching, NOx, and relative humidity observed during environmental chamber experiments. The Journal of Physical Chemistry, Part A, 125, 33, 7303–7317, 2021.
  • K. Patel, M.J. Campmier, S. Bhandari, N. Baig, G. Habib, J.S. Apte*, L. Hildebrandt Ruiz*. Persistence of Primary and Secondary Pollutants in Delhi: Concentrations and Composition from 2017 through the COVID Pandemic. Environmental Science and Technology Letters, 8, 7, 492–497, 2021,
  • Erin F. Katz, Hongyu Guo, Pedro Campuzano-Jost, Douglas A. Day, Wyatt L. Brown, Erin Boedicker, Matson Pothier, David M. Lunderberg, Sameer Patel, Kanan Patel, Patrick L. Hayes, Anita Avery, Lea Hildebrandt
  • Ruiz, Allen H. Goldstein, Marina E. Vance, Delphine K. Farmer, Jose L. Jimenez, Peter F. DeCarlo*. Quantification of Cooking Organic Aerosol in the Indoor Environment Using Aerodyne Aerosol Mass Spectrometers. Aerosol Science and Technology, 55, 10, 1099-1114, 2021,
  • Sarah L. Guberman VerPloeg*, Adelaide E. Clark, Subin Yoon, Lea Hildebrandt Ruiz, Rebecca J. Sheesley, and Sascha Usenko. Assessing the atmospheric fate of pesticides used to control mosquito populations in Houston, TX. Chemosphere, 275, 129951, 2021.
  • K. Patel, S. Bhandari, S. Gani, M.J. Campmier, P. Kumar, G. Habib, J.S. Apte*, L. Hildebrandt Ruiz*. Sources and dynamics of submicron aerosol during the autumn onset of the air pollution season in Delhi, India. ACS Earth and Space Chemistry, 5 (1), 118-128, 2021.
  • Subin Yoon, Stephanie M. Ortiz, Adelaide E. Clark, Tate E. Barrett, Sascha Usenko, Rachelle M. Duvall, Lea Hildebrandt Ruiz, Jeffrey K. Bean, Cameron B. Faxon, James H. Flynn III, Barry L. Lefer, Yu Jun Leong, Robert J. Griffin, and Rebecca J. Sheesley*. Apportioned primary and secondary organic aerosol during pollution events of DISCOVER-AQ Houston. Atmospheric Environment, 244, 117954, 2021.
  • Juan C. Gonzales-Rivera, Kevin C. Baldridge, J.C.L. Chuvalo-Abraham, D.S. Wang, K. Patel, L. Hildebrandt Ruiz, and L. Contreras*. RNA oxidation in chromatin modification and DMA-damage response following exposure to formaldehyde, Scientific Reports, 10 16545, 2020.
  • Wyatt L. Brown, Douglas A. Day, Harald Stark, Demetrios Pagonis, Jordan E. Krechmer, Xiaoxi Liu, Derek J. Price, Erin F. Katz, Peter F. DeCarlo, Catherine G. Masoud, Dongyu S. Wang, Lea Hildebrandt Ruiz, Caleb Arata, David M. Lunderberg, Allen H. Goldstein, Delphine K. Farmer, Marina E. Vance, Jose L. Jimenez*. Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry. Indoor Air, 31 (1), 141-155, 2021,
  • Juan C. Gonzalez-Rivera, Kevin C. Baldridge , Dongyu S. Wang , Kanan H. Patel, Jamie C. L. Chuvalo-Abraham, Lea Hildebrandt Ruiz, and M. Lydia Contreras*. Post-transcriptional air pollution oxidation to the cholesterol biosynthesis pathway promotes pulmonary stress phenotypes, Communications Biology, 3, 392, 2020.
  • S. Gani, S. Bhandari, K. Patel, S. Seraj, P. Soni, Z. Arub, G. Habib, L. Hildebrandt Ruiz*, and J. S. Apte*: Particle number concentrations and size distribution in a polluted megacity: The Delhi Aerosol Supersite study, Atmos. Chem. Phys., 20, 8533-8549, 2020.
  • Z. Arub, S. Bhandari, S. Gani, J. S. Apte, L. Hildebrandt Ruiz, and G. Habib*: Air mass physio-chemical characteristics over New Delhi: Impacts on aerosol hygroscopicity and CCN formation, Atmos. Chem. Phys., 20, 6953-6971, 2020. doi: 10.5194/acp-20-6953-2020.
  • Kanan Patel, Dongyu S. Wang, Puneet Chhabra, Jeffrey Bean, Surya Venkatesh Dhulipala, L. Hildebrandt Ruiz*. Effects of Sources and Meteorology on Ambient Particulate Matter in Austin, Texas. ACS Earth and Space Chemistry, 4, 4, 602-613, 2020. doi:10.1021/acsearthspacechem.0c00016
  • Leigh R. Crilley, Ajit Singh, Louisa J. Kramer, Marvin D. Shaw, Mohammed S. Alam, Joshua S. Apte, William J. Bloss, Lea Hildebrandt Ruiz, Pingqing Fu, Weiqi Fu, Shahzad Gani, Michael Gatari, Evgenia Ilyinskaya, Alastair C. Lewis, David Ng'ang'a, Yele Sun, Rachel C. W. Whitty, Siyao Yue, Stuart Young, and Francis D. Pope. Effect of aerosol composition on the performance of low-cost optical particle counter correction factors. Atmospheric Measurement Techniques, 13, 1181–1193, 2020.
  • J. M. Mattila, P. S. J. Lakey, M. Shiraiwa, C. Wang, J. P.D. Abbatt, C. Arata, A. H. Goldstein, L. Ampollini, E. F. Katz, P. F. DeCarlo, S. Zhou, T. F. Kahan, F. J. Cardoso-Saldaña, L. Hildebrandt Ruiz, A. Abeleira, E. K. Boedicker, M. E. Vance, D. K. Farmer. Multiphase chemistry controls inorganic chlorinated and nitrogenated compounds in indoor air during bleach cleaning. Environmental Science and Technology, 54, 3, 1730-1739, 2020.
  • S. Bhandari, S. Gani, K. Patel, D.S. Wang, P. Soni, Z. Arub, G. Habib, J.S. Apte, L. Hildebrandt Ruiz*. Sources and atmospheric dynamics of organic aerosol in New Delhi, India: Insights from receptor modeling. Atmospheric Chemistry and Physics, 20, 735–752, 2020.
  • D. Hagan, G. Shahzad, S. Bhandari, K. Patel, G. Habib, J. Apte, L. Hildebrandt Ruiz, and J. Kroll*. Inferring Aerosol Sources from Low-Cost Air Quality Sensor Measurements: A Case Study in Delhi, India. Environmental Science and Technology Letters, 6, 8, 467- 472, 2019, doi: 10.1021/acs.estlett.9b00393.
  • D.K. Farmer*, M.E. Vance, J.P.D. Abbatt, A. Abeleira, M.R. Alves, C. Arata, E. Boedicker, S. Bourne, F. Cardoso-Saldaña, R. Corsi, P.F. DeCarlo, A.H. Goldstein, V.H. Grassian, L. Hildebrandt Ruiz, J.L. Jimenez, T.F. Kahan, E.F. Katz, J.M. Mattila, W.W. Nazaroff, A. Novoselac, V.W. Or, R.E. O’Brien, S. Patel, S. Sankhyan, P. S. Stevens, Y. Tian, M. Wade, C. Wang, S. Zhou, Y. Zhou. Overview of HOMEChem: House Observations of Microbial and Environmental Chemistry, Environmental Science: Processes & Impacts, 21, 1280–1300, 2019.
  • S. Gani, S. Bhandari, S. Seraj, D. S. Wang, K. Patel, P. Soni, Z. Arub, G. Habib, L. Hildebrandt Ruiz*, and J. S. Apte*. Submicron aerosol composition in the world's most polluted megacity: The Delhi Aerosol Supersite campaign. Atmospheric Chemistry and Physics, 19, 6843–6859, 2019.
  • S.V. Dhulipala, S. Bhandari, and L. Hildebrandt Ruiz*. Formation of Oxidized Organic Compounds from Cl-Initiated Oxidation of Toluene. Atmospheric Environment, 199, 265-273, 2019.
  • D. S. Wang and L. Hildebrandt Ruiz*. Chlorine-initiated oxidation of n-alkanes under high NOx conditions: Insights into secondary organic aerosol composition and volatility using a FIGAERO-CIMS. Atmospheric Chemistry and Physics, 18, 15535–15553, 2018.
  • C. B. Faxon, S. V. Dhulipala, D. T. Allen and L. Hildebrandt Ruiz*. Heterogeneous Production of Cl2 from Particulate Chloride: Effects of Composition and Relative Humidity. AIChE Journal, 64, 8, 3151 – 3158, 2018.
  • J. K. Bean, S. Bhandari, A. Bilotto and L. Hildebrandt Ruiz*. Formation of particulate matter from the oxidation of evaporated hydraulic fracturing wastewater. Environmental Science and Technology, 52, 8, 4960-4968, 2018.
  • D. S. Wang and L. Hildebrandt Ruiz*. Secondary organic aerosol from chlorine-initiated oxidation of isoprene, Atmospheric Chemistry and Physics, 13491-13508, 17, 2017.
    Y. J. Leong, N. P. Sanchez, H. W. Wallace, B. Karakurt Cevik, C. S. Hernandez, Y. Han, J. H. Flynn, P. Massoli, C. Floerchinger, E. C. Fortner, S. Herndon, J. K. Bean, L. Hildebrandt Ruiz, W. Jeon, Y. Choi, B. Lefer, R. J. Griffin*: Overview of Surface Measurements and Spatial Characterization of Submicron Particulate Matter during the DISCOVER-AQ 2013 Campaign in Houston, The Journal of the Air & Waste Management Association 67, 8, 854-872, 2017.
  • A. Kiendler-Scharr*, A. A. Mensah, E. Friese, D. Topping, E. Nemitz, A. S. H. Prevot, M. Äijälä, J. Allan, F. Canonaco, M. Canagaratna, S. Carbone, M. Crippa, M. Dall Osto, D. A. Day, P. De Carlo, C.F. Di Marco, H. Elbern, A. Eriksson, E.Freney, L. Hao, H. Herrmann, L. Hildebrandt, R. Hillamo, J. L. Jimenez, A. Laaksonen, G. McFiggans, C. Mohr, C. O’Dowd, R. Otjes, J. Ovadnevaite, S. N. Pandis, L. Poulain, P. Schlag, K. Sellegri, E. Swietlicki, P. Tiitta, A. Vermeulen, A. Wahner, D. Worsnop, and H.-C. Wu: Organic nitrates from night-time chemistry are ubiquitous in the European submicron aerosol, Geophysical Research Letters, 43, 14, 7735-7744, 2016.
  • J.K. Bean, C.B. Faxon, Y.J. Leong, H.W. Wallace, B.K. Cevik, S. Ortiz, M.R. Canagaratna, S. Usenko, R. Sheesley, R.J. Griffin, and L. Hildebrandt Ruiz*: Composition and Sources of Particulate Matter Measured near Houston, TX: Anthropogenic-Biogenic Interactions, Atmosphere, 7, 73, 2016
  • J.K. Bean and L. Hildebrandt Ruiz*. Gas-particle Partitioning and Hydrolysis of Organic Nitrates Formed from the Oxidation of α-Pinene in Environmental Chamber Experiments. Atmospheric Chemistry and Physics, 2175–2184, 16, 2016.
  • A. 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, 2013-2023, 16, 2016.
  • C. B. Faxon, J. K. Bean and L. Hildebrandt Ruiz*. Inland Concentrations of Cl2 and ClNO2 in Southeast Texas Suggest Chlorine Chemistry Significantly Contributes to Atmospheric Reactivity, Atmosphere, 6, 1487-1506, 2015.
  • M. 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*. In situ formation and spatial variability of particle number concentration in a European megacity. Atmospheric Chemistry and Physics, 15, 10219 - 10237, 2015.
  • L. 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.
  • B. 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.
  • M. 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, D. Ceburnis, 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. Laaksonen, 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.