Wildfire Smoke: Why It's Thick and What It Means

Biomass burning organic aerosol, or BBOA, is a big deal when it comes to air pollution. It's made when stuff like trees and plants burn, and it plays a big role in how our climate and health are affected. The key here is how sticky and gooey this aerosol is, and whether it's one big blob or a few separate parts. These properties aren't fully understood yet. In 2021, scientists collected BBOA samples from wildfires in British Columbia, Canada. They wanted to find out how gooey and how many parts these aerosols have at different levels of humidity. Guess what? All the samples showed two parts: one that likes water (polar) and one that doesn't (nonpolar).

To measure how gooey these particles are, the scientists used a method called "poke-flow viscosity. " Both parts were super gooey, even when the air was a bit humid. We're talking about viscosities over 10^8 Pa s up to 50% relative humidity. That means these particles mix really slowly, taking over 5 hours in some cases. This two-phase, super gooey behavior has important implications. It changes how we should think about BBOA in our weather models. It's like trying to predict the weather without knowing if it's going to rain or not.

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