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Haroula Baliaka

Atmospheric Chemistry • Air Quality • Urban Fires • Aerosols

I'm an Onassis and Resnick Scholar in the final year of my PhD at Caltech, where I work with Professors Paul Wennberg, Nga Lee Ng, and Richard Flagan on atmospheric chemistry and air quality. I apply scientific methods and principles to identify, study, and evaluate air pollution problems related to climate change, urban air quality, wildfire smoke, and post-fire impacts on public health.

When I first started my PhD, I was drawn to a puzzling question: why does Los Angeles, a city that has spent decades cleaning up its air, still struggle with persistently elevated pollution? I started looking at unique chemical signatures of trace elements and isotopes to identify different air pollution sources.

Then, the 2025 Los Angeles fires happened. What had been a study of chronic urban pollution in the LA basin became something much more urgent: understanding the acute, overlapping impacts of wildfire smoke, structural burning, and resuspended ash on communities that were already carrying a disproportionate pollution burden. The fires gave my PhD a new dimension and a sharper sense of purpose.

Haroula Baliaka

Research

Using S isotopes to disentangle S sources in an urban environment

Source apportionment in the Los Angeles basin using sulfur isotope signatures and complementary aerosol measurements. Funded by the Resnick Sustainability Institute.

ASCENT: Trace elements during the LA fires plume

High-time-resolution elemental measurements used to characterize wildfire plume composition and distinguish fire-enhanced signals from urban background sources. Part of the NSF Atmospheric Science and Chemistry mEasurement NeTwork spanning 12 institutions.

PHOENIX: post-fire air quality impacts during debris removal

Neighborhood-scale monitoring designed to understand post-fire particulate resuspension, debris removal impacts, and community exposure. Deployed following the 2025 Eaton Fire in Altadena; generated 11,000+ website views and provided critical data to community members and LA County Public Health.

Publications

  • Baliaka, H.D., Ward, R.X., Raffuse, S.M., Ries, B., Cui, Y., Wu, D., Liu, R., Barut, C., Hasheminassab, S., Tissot, F., Russell, A., Seinfeld, J.H., Flagan, R.C., Wennberg, P.O., Bahreini, R., Ng, N.L. (2026). Fire at the boundary: airborne toxic metals from the 2025 Los Angeles urban firestorm. ChemRxiv Preprint. doi:10.26434/chemrxiv.15002335/v1
  • Chen, H., Nie, Q., Yu, Q., Li, J., Niu, M., Yao, Y., Boo, P., Kyi, A., Chao, C.-Y., Deveraux, E., Sung, D.H., Lin, C.-H., Neville, A.C., Blankenship, V., Baliaka, H.D., Flagan, R., Ng, N.L., Bahreini, R., Dillner, A.M., Russell, A.G., Misztal, P.K., Hildebrandt Ruiz, L., Zhu, Y. (2026). Characterizing postfire fine and ultrafine particles in the 2025 Eaton Fire burn zone and nearby areas. Environmental Science & Technology Letters. doi:10.1021/acs.estlett.6c00123
  • Baliaka, H.D., Ward, R.X., Bahreini, R., Dillner, A.M., Russell, A.G., Seinfeld, J.H., Flagan, R.C., Wennberg, P.O., Ng, N.L. (2025). Notes from the field: Elevated atmospheric lead levels during the Los Angeles urban fires --- California, January 2025. CDC MMWR. doi:10.15585/mmwr.mm7405a4
  • Murphy, S.E., Buenconsejo, R.S., Draper, D.C., Crounse, J.D., Baliaka, H.D., Ward, R.X., Schulze, B.C., Rezgui, S.P., Ball, K., Susskind, T., Kappaganthula, G., Wennberg, P.O. (2025). Multi-functional Organic Nitrogen in the Los Angeles Air Basin. ACS ES&T Air. doi:10.1021/acsestair.5c00206
  • Ward, R.X., Baliaka, H.D., Schulze, B.C., Kerr, G.H., Crounse, J.D., Hasheminassab, S., Bahreini, R., Dillner, A.M., Russell, A., Ng, N.L., Wennberg, P.O., Flagan, R.C., Seinfeld, J.H. (2025). Poorly quantified trends in ammonium nitrate remain critical to understand future urban aerosol control strategies. Science Advances. doi:10.1126/sciadv.adt8957
  • Kaltsonoudis, C., Florou, K., Kodros, J.K., Jorga, S.D., Vasilakopoulou, C.N., Baliaka, H.D., Matrali, A., Aktypis, A., Georgopoulou, M.P., Nenes, A., Pandis, S.N. (2024). Significant contributions of fresh and aged biomass burning organic aerosol from residential burning in a wintertime urban environment. Atmospheric Environment. doi:10.1016/j.atmosenv.2024.121018

Presentations

Conference Presentations

  • ACS Spring Meeting • Atlanta, GA, 2026 • Oral
    Real-Time Trace Element Insights from the 2025 LA Eaton Firestorm
  • Air Sensors International Conference • Los Angeles, CA, 2026 • Oral
    PHOENIX: Dense sensor network for PM monitoring
  • AGU Fall Meeting • New Orleans, LA, 2025 • Oral
    PHOENIX: Dense sensor network for PM monitoring
  • AAAR Annual Conference • Buffalo, NY, 2025 • Oral
    Real-Time Trace Elements from 2025 LA Eaton Firestorm
  • 1st Annual LA Fires Research Conference • UCLA, 2025 • Poster (2 presentations)
  • AGU Fall Meeting • Washington, DC, 2024 • Poster
    Yearlong variability and source apportionment of PM2.5
  • AAAR Annual Conference • Albuquerque, NM, 2024 • Oral
    Impact of ambient particulate metals in Los Angeles
  • AAAR Annual Conference • Portland, OR, 2023 • Poster
    Characterizing LA aerosol through high-resolution measurements
  • International Aerosol Conference • Athens, Greece, 2022 • Oral
    Secondary organic aerosol formation from volatile chemical products
  • IGASP • UC Irvine, CA, 2022 • Poster
    Source apportionment of brown carbon

Invited Talks

  • University of Washington, ENV H 580 • April 30, 2026
    Environmental and Occupational Health Seminar
  • 9zero Climate Innovation Hub • Seattle, WA • April 30, 2026
  • California State University Fullerton • April 9, 2026
    Chemistry and Biochemistry Department
  • University of Washington, ATMOS 523 • February 23, 2026
    Atmospheric Physics and Chemistry Seminar
  • Caltech, BEES • April 29, 2025
    Breakfast Exchange in Environment & Sustainability
  • Caltech, RSI Seminar • October 30, 2023
    Resnick Sustainability Institute

Public Webinars

  • Environmental Impacts of Fires at Wildland–Urban Interface
    Caltech Science Exchange • ~2,000 attendees • Jan 31, 2025
  • Conversations After the Fires: Air Quality and Health
    Caltech Science Exchange • ~600 attendees • May 2, 2025
  • Three Minute Thesis (3MT) Finalist
    Watch on YouTube

Media Coverage

Curriculum Vitae

For a complete overview of my education, awards, experience, and publications, please download my full curriculum vitae:

Download Full CV (PDF)

Teaching & Mentoring

Teaching Assistant (Sep 2022–present)

  • Atmospheric Chemistry I (ESE/Ge/Ch 171)
  • Climate Change Impacts, Mitigation and Adaptation (ESE/ME/EST/Ec/ChE/EE 179)
  • Mentoring and Outreach for GO-Outdoors (Ge/ESE 298; 3 quarters)

Guest Lecturer (2023–2026)

  • Current Problems in Environmental Science and Engineering (ESE 104; 2024, 2026)
  • Environmental Impacts of Wildfire (ESE 200; 2025)
  • Atmospheric Chemistry I (ESE 171; 2023)

SURF Student Mentor (Summer 2024)

  • Mentored undergraduate researcher on "Evolution of black and brown carbon in the Los Angeles Basin"
    Received Caltech's Certificate of Interest in Undergraduate Research Mentoring

Outreach

  • Mar 2026 — Conference Symposium Co-Organizer, American Chemical Society Spring Meeting, Atlanta, GA
    Co-led "Wildland Urban Interface (WUI) Fire Impacts on Environmental Systems" and served as session presider
  • 2021–2025 — ASCENT Standard Operating Procedures Student Committee Member, NSF Atmospheric Science and Chemistry mEasurement NeTwork
    Coordinated protocols across 12 institutions. Received Certificate of Appreciation
  • 2022–2024 — Lab Safety Officer, Seinfeld Group, Caltech
  • 2024 — Scientific Outreach Event Co-Organizer, Caltech
    Linde Center Open House (100 participants) and Two-day Science Symposium (150 participants)
  • 2024 — International Student Programs (ISP) Orientation Leader, Caltech
  • 2023–2024 — GO-Outdoors Program Lead, Caltech
    Developed lesson plans, doubled reach to 1,000+ students from underrepresented schools
  • 2022–present — Founder & President, Hellenic Students Association of Caltech