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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

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
CHE 384 Professional Development for Engineering PhD Students

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
  • National Science Foundation (NSF) Postdoctoral Research Fellowship, 2011 – 2012
  • EPA Graduate Research Fellowship, 2010 – 2011
  • NSF Graduate Research Fellowship, 2006 – 2009

Selected Publications

  • Catherine Masoud, Mrinali Modi, Nirvan Bhattacharyya, Leif Jahn, Kristi McPherson, Pearl Abue, Kanan Patel, David Allen, Lea Hildebrandt Ruiz*. High chlorine concentrations in an unconventional oil and gas development region and impacts on atmospheric chemistry. Environmental Science and Technology, 2023.
  • Nirvan Bhattacharyya, Mrinali Modi, Leif G. Jahn, and Lea Hildebrandt Ruiz*. Different Chlorine and Hydroxyl Radical Environments Impact m-xylene Oxidation Products. Environmental Science, Atmospheres, 3, 1174-1185, 2023.
  • Kanan Patel, Sahil Bhandari, Shahzad Gani, Purushottam Kumar, Nisar Baig, Gazala Habib, Joshua Apte*, Lea Hildebrandt Ruiz*. Factors Influencing Ambient Particulate Matter in Delhi, India: Insights from Machine Learning. Aerosol Science and Technology, 57, 6, 546–561, 2023.
  • Nirvan Bhattacharyya, Mengjia Tang, Daniel Blomdahl, Leif Jahn, Pearl Abue, David Allen, Richard Corsi, Atila Novoselac, Pawel Misztal, Lea Hildebrandt Ruiz. “Bleach Emissions Interact Substantially with Surgical and KN95 Mask Surfaces”. Environmental Science and Technology, 57, 16, 6589–6598, 2023.
  • Anita Avery, Mitchell Alton, Manjula Canagaratna, Jordan Krechmer, Donna Sueper, Nirvan Bhattacharyya, Lea Hildebrandt Ruiz, William Brune, Andrew Lambe*. Comparison of the yield and chemical composition of secondary organic aerosol generated from the OH and Cl oxidation of decamethylcyclopentasiloxane. ACS Earth and Space Chemistry, 7, 1, 218–229, 2023.
  • Leif G. Jahn, Mengjia Tang, Daniel Blomdahl, Nirvan Bhattacharyya, Pearl Abue, Atila Novoselac, Lea Hildebrandt Ruiz*, and Pawel K. Misztal*. Volatile organic compound (VOC) emissions from the usage of benzalkonium chloride and other disinfectants based on quaternary ammonium compounds. Environmental Science: Atmospheres, 3, 363-373, 2023.
  • Catherine G. Masoud, Ying Li, Dongyu S. Wang, Erin F. Katz, Peter F. DeCarlo, Delphine K. Farmer, Marina E. Vance, Manabu Shiraiwa, Lea Hildebrandt Ruiz*. Molecular composition and gas-particle partitioning of indoor cooking aerosol: Insights from a FIGAERO-CIMS and kinetic aerosol modeling. Aerosol Science and Technology, 56, 12, 1156-1173, 2022.
  • Sahil Bhandari, Zainab Arub, Gazala Habib, Joshua S. Apte*, and Lea Hildebrandt Ruiz*. Contributions of primary sources to submicron organic aerosols in Delhi, India. Atmospheric Chemistry and Physics, 22, 13631–13657, 2022.
  • Sahil Bhandari, Zainab Arub, Gazala Habib, Joshua S. Apte*, and Lea Hildebrandt Ruiz*. Source apportionment resolved by time-of-day for improved deconvolution of primary source contributions to air pollution. Atmospheric Measurement Techniques, 15, 6051–6074, 2022.
  • Dongyu S. Wang, Catherine G. Masoud, Mrinali Modi, and Lea Hildebrandt Ruiz*. Impacts of chlorine chemistry on urban air quality: Isoprene-chlorine oxidation in the presence of NOx. Environmental Science and Technology, 56, 13, 9251–9264, June 2022.
  • 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, September 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.
  • 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.
  • 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. 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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,
  • 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.
  • 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.