Laura Marie Dahler Heinlein

Wildfire smoke is composed of particles that travel through Earth’s atmosphere for up to two weeks. During this process, the wildfire smoke particles undergo chemical aging, which alters a particle’s toxicity and its impact on climate. I study the reactive chemical species formed inside wildfire smoke particles when the sun shines that contribute to this chemical aging.

Biomass burning (BB) is a major source of particulate matter pollution in the United States. Whether from wildfire smoke, agricultural burns, or residential wood burning, millions of Americans breathe in BB smoke. After smoke is emitted, particles reside in the atmosphere for approximately two weeks during which their chemical composition undergoes a dramatic transformation, called chemical aging. BB particles are rich in brown carbon (BrC), a class of light absorbing organic compounds. When BrC absorbs light, it forms photooxidants – reactive species that are involved in the chemical aging of particles. Specifically, photooxidants can change a particle’s chemical composition, size, toxicity, and impact on climate. While up to 80% of BrC is not water soluble, the only measurements of BrC photooxidants are from water-soluble BrC. Here, we develop a method to quantify photooxidants from water insoluble BrC. Next, we will make the first-ever measurements of BrC photooxidants from water-insoluble BrC collected from wildfire smoke. This work expands our understanding of particle chemistry in wildfires smoke, providing insight into the complex chemical aging of wildfire smoke particles.