photosensitizer; viscosity; aerosol; photochemistry; atmospheric chemistry; organic aerosol
Alpert Peter A., Dou Jing, Corral Arroyo Pablo, Schneider Frederic, Xto Jacinta, Luo Beiping, Peter Thomas, Huthwelker Thomas, Borca Camelia N., Henzler Katja D., Schaefer Thomas, Herrmann Hartmut, Raabe Jörg, Watts Benjamin, Krieger Ulrich K., Ammann Markus (2021), Photolytic radical persistence due to anoxia in viscous aerosol particles, in Nature Communications
, 12(1), 1769-1769.
Dou Jing, Alpert Peter A., Corral Arroyo Pablo, Luo Beiping, Schneider Frederic, Xto Jacinta, Huthwelker Thomas, Borca Camelia N., Henzler Katja D., Raabe Jörg, Watts Benjamin, Herrmann Hartmut, Peter Thomas, Ammann Markus, Krieger Ulrich K. (2021), Photochemical degradation of iron(III) citrate/citric acid aerosol quantified with the combination of three complementary experimental techniques and a kinetic process model, in Atmospheric Chemistry and Physics
, 21(1), 315-338.
Alpert Peter A., Corral Arroyo Pablo, Dou Jing, Krieger Ulrich K., Steimer Sarah S., Förster Jan-David, Ditas Florian, Pöhlker Christopher, Rossignol Stéphanie, Passananti Monica, Perrier Sebastien, George Christian, Shiraiwa Manabu, Berkemeier Thomas, Watts Benjamin, Ammann Markus (2019), Visualizing reaction and diffusion in xanthan gum aerosol particles exposed to ozone, in Physical Chemistry Chemical Physics
, 21(37), 20613-20627.
Dou Jing, Luo Beiping, Peter Thomas, Alpert Peter A., Corral Arroyo Pablo, Ammann Markus, Krieger Ulrich K. (2019), Carbon Dioxide Diffusivity in Single, Levitated Organic Aerosol Particles, in The Journal of Physical Chemistry Letters
, 10(15), 4484-4489.
Liati A., Schreiber D., Alpert P.A., Liao Y., Brem B.T., Corral Arroyo P., Hu J., Jonsdottir H.R., Ammann M., Dimopoulos Eggenschwiler P. (2019), Aircraft soot from conventional fuels and biofuels during ground idle and climb-out conditions: Electron microscopy and X-ray micro-spectroscopy, in Environmental Pollution
, 247, 658-667.
Corral Arroyo Pablo, Aellig Raffael, Alpert Peter A., Volkamer Rainer, Ammann Markus (2019), Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry, in Atmospheric Chemistry and Physics Discussions
, in press, 1-18.
Bastelberger S., Krieger U. K., Luo B. P., Peter Th. (2018), Time evolution of steep diffusion fronts in highly viscous aerosol particles measured with Mie resonance spectroscopy, in The Journal of Chemical Physics
, 149(24), 244506-244506.
Arroyo Pablo Corral, Malecha Kurtis T., Ammann Markus, Nizkorodov Sergey A. (2018), Influence of humidity and iron( iii ) on photodegradation of atmospheric secondary organic aerosol particles, in Physical Chemistry Chemical Physics
, 20(47), 30021-30031.
Corral Arroyo Pablo, Bartels-Rausch Thorsten, Alpert Peter A., Dumas Stéphane, Perrier Sébastien, George Christian, Ammann Markus (2018), Particle-Phase Photosensitized Radical Production and Aerosol Aging, in Environmental Science & Technology
, 52(14), 7680-7688.
Berkemeier Thomas, Ammann Markus, Krieger Ulrich K., Peter Thomas, Spichtinger Peter, Pöschl Ulrich, Shiraiwa Manabu, Huisman Andrew J. (2017), Technical note: Monte Carlo genetic algorithm (MCGA) for model analysis of multiphase chemical kinetics to determine transport and reaction rate coefficients using multiple experimental data sets, in Atmospheric Chemistry and Physics
, 17(12), 8021-8029.
González Palacios Laura, Corral Arroyo Pablo, Aregahegn Kifle Z., Steimer Sarah S., Bartels-Rausch Thorsten, Nozière Barbara, George Christian, Ammann Markus, Volkamer Rainer (2016), Heterogeneous photochemistry of imidazole-2-carboxaldehyde: HO<sub>2</sub> radical formation and aerosol growth, in Atmospheric Chemistry and Physics
, 16(18), 11823-11836.
Berkemeier Thomas, Steimer Sarah S., Krieger Ulrich K., Peter Thomas, Pöschl Ulrich, Ammann Markus, Shiraiwa Manabu (2016), Ozone uptake on glassy, semi-solid and liquid organic matter and the role of reactive oxygen intermediates in atmospheric aerosol chemistry, in Physical Chemistry Chemical Physics
, 18(18), 12662-12674.
Aerosol aging refers to the multitude of physical and chemical transformation atmospheric particles undergo, which play an important role in the impact of aerosols on climate, air quality and health. In this project, we consider indirect photochemical processes, which catalyze redox processes of non-absorbing molecules. Indirect photochemistry is especially relevant in the lower troposphere where UV light intensity with sufficiently low wavelengths to directly photolyze the major organic or inorganic aerosol components is low. Important indirect photochemical processes are transition metal complex photochemistry and photosensitized processes. Iron (Fe(III)) carboxylate complexes absorb light below about 500 nm, which leads to reduction of iron to Fe(II) and oxidation of the carboxylate ligands, a process that represents an important sink of organic acids in the troposphere. Photosensitizers, such as aromatic ketones or imidazoles, form triplet excited states which initiate redox processes with other compounds. Photosensitized processes provide an important contribution to condensed phase radical production, to fragmentation of organics and also to buildup of secondary organic matter. The radical induced oxidation processes in turn also affect the microphysical properties through building up products exhibiting different hydration properties. Furthermore, some of the products of condensed phase oxidation may themselves be chromophores, which may induce an increase in the absorbance of aerosol particles (cf brown carbon) but which may also be active as photosensitizers. It has recently been recognized that aqueous aerosol particles may attain highly viscous, semi-solid or even glassy physical states under a wide range of conditions in the atmosphere. While the impact of reduced mobility of aerosol constituents in high viscosity particles on dark chemical reactions has received substantial attention over the past five years, systematic studies on the effect of high viscosity on photochemical processes are scarce. The reduced mobility and low water content in highly viscous particles impacts on the indirect photochemical processes through affecting the initial absorption process, charge and energy transfer, and by preventing diffusion of intermediates. In turn, the formation of higher molecular weight and more oxygenated products mix may lead to an increase in viscosity of the particles. Thus, a multitude of feedbacks exist that link microphysics and photochemistry in aerosol particles. The approach in this joint project between the ‘Ammann group’ at PSI and the ‘Krieger group’ at ETH follows directly on our previous work, where we have established a link between microphysics and dark oxidation processes. We plan to work with three model systems: Fe(III)-citrate induced citric acid degradation, imidazole carboxaldehyde sensitized citric acid degradation, and imidazole carboxaldehyde sensitized oxidation of phenolic biomass burning proxy compounds. Mass, size, water diffusivity, and optical properties of single levitated particles will be measured in an electrodynamic balance at ETH. Spatially resolved O:C ratios, carbon functional group composition, and Fe oxidation state will be measured by in situ scanning transmission X-ray microscopy (STXM). Measurements of product formation rates and assessment of radical budgets and redox activity will be performed in an irradiated coated wall flow tube (CWFT) experiment. In each of these techniques, the model systems will be followed over time as a function of irradiation, RH and temperature. The integration of the results will be assisted by kinetic model tools. It will provide a sound basis to understand the bidirectional feedbacks between indirect photochemical aerosol aging, optical properties and viscosity for the selected particle system.