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.
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.
