Theoretical and synchrotron excited spectroscopic studies of water solutions as model systems of atmospheric cloud droplets

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, auditorium L2

Topic of the dissertation

Theoretical and synchrotron excited spectroscopic studies of water solutions as model systems of atmospheric cloud droplets

Doctoral candidate

Master of Science Georgia Michailoudi

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Nano and Molecular Systems Research Unit

Subject of study

Atmospheric physics

Opponent

Associate Professor Jenny Rissler, Lund University

Custos

Associate Professor Nønne L. Prisle, University of Oulu

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Theoretical and synchrotron excited spectroscopic studies of water solutions as model systems of atmospheric cloud droplets

Aerosol particles play significant roles in atmospheric processes but their effects pose large uncertainties in climate predictions. This thesis presents computational and experimental studies of aqueous organic and organic–inorganic solutions that serve as model systems of cloud droplets for better understanding of aerosols and their impact on climate.
Carbon and oxygen K-edge X-ray Absorption Spectroscopy (XAS) has been applied in order to study molecular level interactions in aqueous solutions of glyoxal and methylglyoxal and to investigate potential salting effects with addition of inorganic salts to the solutions. The spectra were used for identification of chemical bonds and hydrated forms in the solutions.
Carbon K-edge XAS was applied also for the study of binary aqueous solutions comprising surfactants- sodium hexanoate and sodium octanoate. The solutions were measured for concentrations of solutes above and below the critical micelle concentration in order to observe the formation of micelles in the solution. In the case of aqueous sodium octanoate changes in the shapes of the spectra with increasing concentrations suggest changes in the chemical environment of the carbon atoms that could possibly be related to micelle formation.
COSMOtherm, a software based on COSMO-RS (COnductor like Screening MOdel for Real Solvents), was used to predict solubilities and activity coefficients for C2–C12 fatty acids with even number of carbon atoms and their sodium salts in binary aqueous solutions and also in ternary solutions, comprising inorganic salts. The computed values indicate that COSMOtherm can be used to provide information about atmospheric organic components of aqueous solutions where experimental data are currently inaccessible. The results of these studies contribute to understanding of cloud microphysics and may be used to improve accuracy of atmospheric model predictions.
Last updated: 10.8.2021