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Shining light on oxidants in the atmosphere: The case of singlet oxygen from aqueous organic aerosols
Speaker Name
Dr. Nadine Borduas-Dedekind
Speaker Detail

SNSF Ambizione Fellow
Department of Environmental Systems Science
ETH Zurich, Switzerland

Online Platform via Zoom
Meeting ID: 958 6484 4148
Password: 682422

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.

About the Speaker

Dr. Nadine Borduas-Dedekind is an atmospheric organic chemist interested in chemical mechanisms, including oxidations and photo-oxidations, in the gas phase and in the aerosol phase. She has a BSc and a MSc in organic chemistry, and worked in the pharmaceutical industry. She then pursued a PhD in atmospheric chemistry at the University of Toronto. After working in air quality consulting in South Africa and in aquatic photochemistry as a postdoc in Switzerland, Nadine is currently a SNSF Ambizione Fellow at ETH Zurich hosted in the environmental chemistry and atmospheric physics groups. Ongoing research interests include reactive oxygen species produced during photochemical exposure of aerosols and organic matter acting as atmospheric ice nuclei. Nadine is moving to the University of British-Columbia in January 2021 to start as an Assistant Professor in Chemistry to study chemical mechanisms indoors and outdoors using mass spectrometry.