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Reactive oxygen species in the atmosphere: the significance of singlet oxygen production within aqueous organic aerosols

Research profile seminar

Abstract
Organic aerosols have an atmospheric lifetime of approximately one week. During this time, these aerosols will be subjected to atmospheric processing including exposure to sunlight. Photochemistry of organic aerosols produces reactive oxygen species (ROS) in-situ capable of transforming their chemical and physical properties, with implications for air quality and climate. In surface aquatic environments rich in organic matter, singlet oxygen (1O2) concentrations are typically 1000 times higher than OH radical concentrations. Although 1O2 is a selective oxidant, we wondered whether it would also be present within secondary organic aerosol (SOA) and whether its steady-state concentrations were elevated enough to impact the degradation of key organic aerosol tracers. Using furfuryl alcohol as a probe for 1O2, we determined steady-state concentrations of this oxidant and calculated 1O2 quantum yields for SOA samples. Subsequent quantification of OH radicals and peroxides allowed for the comparison of degradation rates between ROS species. We find that for typical molecules found in SOA such as amino acids (histidine, tryptophan, methionine), organo-nitrogen compounds (imidazole, indole, niclosamide) and phenolic compounds (hydroquinone, resorcinol) have a shortened lifetime by more than half when 1O2 reactivity is taken into consideration. To further understand the seasonal variability of 1O2, we are currently working on a one-year time series of PM10 filters collected in Switzerland. It is becoming clear that 1O2 could be an important photo-generated oxidant within aqueous organic aerosols for the degradation of aerosol tracer molecules.

Lecturer: Nadine Borduas-Dedekind (https://usys.ethz.ch/en/people/profile.MjI5NjY5.TGlzdC82MzcsMzIwMTk3MjIy.html)

Date: 10/24/2019

Time: 12:00 PM - 1:00 PM

Categories: Science

Location: Room KC, Chemistry Building, Campus Johanneberg

Contact person: Erik Thomson

Page Manager: |Last update: 1/2/2012
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