Ph. D. (Environmental Chemistry), University of Toronto, 2013
Thesis Advisor: Dr. D. J. Donaldson
B. Ed. (Intermediate/Senior Chemistry and Mathematics), Ontario Institute for Studies in Education/University of Toronto, 2007
B. Sc. (Honours) Chemistry, Queen’s University, 2006
Thesis advisor: Dr. H.- P. Loock
Secondary organic aerosol (SOA) comprise a significant fraction of atmospheric aerosol. However, the formation and evolution of SOA is poorly understood, making it difficult to predict a) the spatial and temporal distribution of SOA, as well as its composition and properties – and hence its climate impact and b) how controls on primary emissions might influence SOA levels. Traditional models based on reversible gas-to-particle partitioning of semi-volatile organics cannot reproduce SOA observations. Recently, the importance of aqueous-phase processing (for example in cloud droplets or fog water) as a source of SOA has come to attention.
Methylglyoxal (MG) is produced in the atmosphere from both anthropogenic and biogenic precursors and its uptake to aqueous aerosols and cloud droplets is thought to play an important role in SOA formation. MG uptake to aqueous particles is higher than expected due to the fact that its carbonyl moieties can hydrate to form diols, as well as the fact that MG can undergo aldol condensation reactions to form larger oligomers in solution. These reactions can be further catalyzed by certain inorganic salts (such as ammonium) which are also common constituents of aerosols. MG is known to be surface active but an improved description of its surface behaviour is crucial to understanding MG-SOA formation, in addition to understanding its gas-to-particle partitioning and cloud forming potential. Some questions we are interested in include: Does MG exist in a hydrated form at the interface? How does the presence and identity of different salts influence MG’s surface activity and orientation at the interface? Are MG oligomers present at the air-water interface?
We are using vibrational sum frequency spectroscopy (VSFS) to study MG at the air-water interface, in the presence and absence of salts. This work is being complemented by interfacial tension studies and bulk Raman spectroscopic studies. Further interpretation of experimental results is aided by computation studies (molecular dynamics studies and density functional theory calculations) of methylglyoxal and hydrated methylglyoxal (diol and tetrol).
I obtained my Ph. D. in Environmental Chemistry from the University of Toronto in 2013. My Ph. D. research focused on using surface-sensitive spectroscopic techniques (glancing-angle Raman spectroscopy and glancing-angle laser induced fluorescence) to investigate physical and chemical properties of the air-ice interface. I joined the Richmond Group as a post-doctoral research associated in October, 2013. I’m looking forward to applying sum frequency generation spectroscopy (yay lasers!) to the study of atmospherically relevant processes at air-water interfaces. Outside of the lab I enjoy being active (swimming, running, snowboarding, playing hockey, soccer and squash), getting crafty (sharpie doodling and pottery), playing the piano, cooking, curling up with a good book, and chilling with friends.
- Accepted: Donaldson, D. J., Wren, S. N., “Laboratory Kinetics”, revision of original, submitted to “Encyclopedia of Atmospheric Science, 2nd Ed.”, J. Holton, J. Pyle and J. Curry, eds.
- Wren, S. N., Donaldson D. J., Abbatt, J. P. D., Photochemical chlorine and bromine activation from artificial saline snow, Atmos. Chem. Phys., 13, 2013, 9789 – 9800
- Hong, A. C., Wren, S. N., Donaldson, D. J., Enhanced surface partitioning of nitrate anion in aqueous bromide solutions, J. Phys. Chem. Lett., 2013
- Bartelt-Rausch, T., Schreiber, S., Wren, S. N., Riche, F., Schneebeli, M., Ammann, M. “Diffusion of volatile organics through porous snow: Impact of surface adsorption and grain-boundaries”, Atmos. Chem. Phys., 13, 2013, 6727-6739
- Wren, S. N., Donaldson, D. J., How does deposition of gas phase species affect pH at frozen salty interfaces?, Atmos. Chem. Phys., 12, 2012, 10065 – 10073
- Abbatt, J. P. D. et al., Wren, S. N., Halogen activation via interactions with environmental ice and snow in the polar lower troposphere and other regions, Atmos. Chem. Phys., 12, 2012, 6237 – 6271
- Wren, S. N., Donaldson, D. J., Laboratory study of pH at the air-ice interface, J. Phys. Chem. C, 116, 2012, 10171–10180
- Wren, S. N., Donaldson, D. J., Glancing-angle Raman study of nitrate and nitric acid at the air–aqueous interface, Chem. Phys. Lett., 522, 2012, 1 – 10 (Cover, Frontiers Article)
- Wren, S. N., Donaldson, D. J., Exclusion of Nitrate to the Air-Ice Interface During Freezing, J. Phys. Chem. Lett., 2, 2011, 1967 – 1971
- Wren, S. N., Kahan, T. F., Jumaa, K. B., Donaldson, D. J., Spectroscopic studies of the heterogeneous reaction between O3(g) and halides at the surface of frozen salt solutions, J. Geophys. Res. Atmos., 115, D16309, 2010
- Wren, S. N. and Donaldson, D. J., Glancing-angle Raman spectroscopic probe for reaction kinetics at water surfaces, Phys. Chem. Chem. Phys., 12, 2010, 2648 – 2654