Detailed model studies on new particle formation and relevant precursors in chamber experiments and ambient atmosphere

• Main Author: Xavier, Carlton
• Other Authors: Karl, Matthias, University of Helsinki, Faculty of Science, INAR, Doctoral Programme in Atmospheric Sciences, Helsingin yliopisto, matemaattis-luonnontieteellinen tiedekunta, Ilmakehätieteiden tohtoriohjelma, Helsingfors universitet, matematisk-naturvetenskapliga fakulteten, Doktorandprogrammet i atmosfärvetenskap, Boy, Michael, Roldin, Pontus
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Helsingin yliopisto 2022
• Subjects: atmospheric Sciences; Arctic
• Online Access: http://hdl.handle.net/10138/344761

Atmospheric aerosols are small, solid, or liquid particles suspended in the air surrounding us. Although small in size, aerosol particles significantly influence human life, by deteriorating the health, air quality in urban centers and influencing climate both directly and indirectly by scattering and absorption of solar radiation and modifying cloud properties. Atmospheric new particle formation (NPF) contributes the major fraction of atmospheric total particle number concentrations. NPF proceeds via the formation of nanometer-sized molecular clusters followed by the subsequent growth to larger sizes, when they can act as cloud condensation nuclei (CCN) and thus potentially affect the climate. The growth of the aerosols in the atmosphere is driven primarily by the condensation of organics or heterogeneous and multi-phase chemistry and is termed as secondary aerosol formation. In this thesis we elucidated the role of secondary aerosol formation and its impact in continental and remote Arctic regions. Additionally, we attempted at quantifying the long-term trends of important atmospheric oxidants (OH and NO3) which potentially impact both NPF and secondary aerosol formation. In spring-time boreal forest (SMEAR II) ion-mediated H2SO4-NH3 clustering could explain 91% of NPF while organics-H2SO4 clustering played a minor role according to our model simulations. Depending on the volatility, highly oxidized organic molecules (HOM), which are formed from the oxidation of volatile organic compounds (VOCs), can contribute to the growth of aerosol particles. Results from simulations performed at SMEAR II indicate that HOM contributes almost 18% to total secondary organic aerosol (SOA) mass concentration. The results further show that HOM SOA can result in a net negative radiative forcing. This negative radiative forcing by HOM SOA is offset by a net positive forcing caused by NPF under certain meteorological conditions. In remote marine environments compounds such as methane sulfonic acid (MSA), which are aqueous-phase ...