Wildfires are becoming more frequent and more intense, resulting in degraded air quality across the country.  After smoke is emitted from a fire, it undergoes chemical processing in the atmosphere, altering its properties as well as impacts on climate and human health. 

In 2019, we conducted field measurements at Mt. Bachelor, Oregon, to understand these atmospheric transformations.  We sampled smoke from fires in the Pacific Northwest and from as far away as Siberia and found that particles from these fires were present throughout the remote atmosphere.  Read the paper here 

We also coupled the 2019 measurements with aircraft measurements collected during the 2013 Biomass Burning Observation Project.  This allowed us to gain an understanding of the lifecycle of smoke particles ranging from minutes after emission to weeks of aging.  From this extensive dataset, we identified the rapid formation of low volatility secondary organic aerosol and added constraints to changes in chemical composition that can be integrated into chemical transport models.  Read the paper here

Catastrophic fires are also occurring more frequently in the Wildland Urban Interface (WUI) where homes and other structures are interspersed with vegetation, such as the 2025 Los Angeles Wildfires and 2023 Lahaina Fire. 

To understand how emissions from fires that burn manmade fuels are different than wildland fires, current work involves analyzing ash samples collected after the Eaton Fire in Altadena, and combustion experiments of plastics.  Early results show enhanced emissions of metals, hydrochloric acid and other air toxics from urban fuels. Stay tuned for publication on this topic!

Chemical reactions can occur within cloud and fog droplets resulting in particulate matter with unique properties.  Additionally, polluted conditions can alter cloud properties by increasing cloud brightness and inhibiting rainfall

To understand the role of anthropogenic emissions on cloud properties we deployed instrumentation to La Jolla, California as part of the Eastern Pacific Cloud and Aerosol Precipitation Experiment (EPCAPE).  During this campaign we measured the composition of both particulate matter and material dissolved in cloud droplets.  We found that cloud droplets had higher concentrations of inorganic salts, specifically nitrate and chloride, which provides evidence for what type of particles act as cloud condensation nuclei in polluted coastal locations.    

We also explored the role of fog processing on particulate matter composition in Fresno, CA.  In the wintertime, Fresno frequently experiences extremely polluted conditions due to residential woodburning for heating.   We examined the composition of soot particles, released by vehicles and wood combustion, and found that fog processing resulted in particles with thick coatings, which can alter light absorption and particle hygroscopicity.  Read the paper here

As a part of the Tracking Aerosol Convection Interactions Experiment (TRACER) we deployed a mass spectrometer to Houston, TX, to measure the particle-resolved composition of soot aerosol.  We found an incredibly diverse range of particle types impacted by local emissions, long-range transport and atmospheric processing.  Although soot particles are generally thought to be hydrophobic, we found many particles were mixed with hydroscopic material, such as sulfate and oxidized organic compounds which greatly increases there ability to act as cloud condensation nuclei.  Read the paper here