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During their lifetime, organic aerosols will be subjected to atmospheric processing including exposure to sunlight. Photochemistry of chromophoric organic matter within aerosols can produce in-situ reactive oxygen species (ROS) capable of transforming chemical and physical properties of aerosols, with implications for air quality and climate. Singlet oxygen (¹O₂) is a well-known ROS in biology and in surface waters, yet there is little knowledge of its atmospheric sources and sinks, and consequently of its ability to alter aerosol chemistry.

To address this knowledge gap, we generated secondary organic aerosols from aromatic anthropogenic precursors in a laboratory smog chamber. We then extracted the collected SOA filters and submitted the soluble extracts to atmospherically-relevant photochemical conditions. Using furfuryl alcohol as a probe for ¹O₂, we determined steady-state concentrations of this oxidant and calculated ¹O₂ quantum yields for each SOA sample. Subsequent quantification of OH radicals and peroxides allowed for the comparison of degradation rates between ROS. We find that molecules such as amino acids, organo-nitrogen compounds and phenolic compounds have a shortened lifetime by more than half when ¹O₂ reactivity is taken into consideration. Our ongoing work is looking at the photoproduction of ¹O₂ in ambient PM₁₀ filter samples and its potential source apportionment.