Biomass-burning organic aerosols boost air pollutant formation under sunlight

What is it about?

This research explores how organic particles emitted from burning biomass contribute to sulfate formation in the atmosphere. These particles contain special light-absorbing molecules called photosensitizers, which are excited to reactive states upon exposure to sunlight. We experimentally investigated how biomass burning particles promote the conversion of gaseous sulfur dioxide into particulate sulfate through the action of these photosensitizers. Our findings demonstrate how wildfires and biomass burning can worsen air pollution by accelerating atmospheric reactions under sunlight.

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Photo by Malachi Brooks on Unsplash

Photo by Malachi Brooks on Unsplash

Why is it important?

Sulfate is a major component of atmospheric particles that significantly contribute to respiratory diseases, resulting in millions of premature deaths worldwide each year. This study sheds light on the previously unexplained high levels of sulfate observed during haze events. Moreover, it is increasingly recognized that wildfire events release ‘brown’ particles into the atmosphere, which influence the Earth's radiative balance by absorbing sunlight. However, less attention has been given to the chemical reactivity of these light-absorbing particles under sunlight. While atmospheric reactions are generally considered driven by gaseous oxidants, we demonstrate that the oxidants can also be effectively generated within those light-absorbing biomass-burning particles under sunlight, as indicated by the rapid sulfate formation. These findings not only improve our understanding of atmospheric reaction mechanisms but also raise awareness about the formation of air pollutants linked to wildfires, particularly as climate change increases the frequency and severity of these events.

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