Atmospheric sub-10 nm aerosol number size distributions : measurement, analysis and implications

New particle formation (NPF) is a major source of atmospheric aerosol in terms of number concentration. As the newly formed particles grow, they can affect climate both directly and indirectly. However, understanding the first steps of NPF is an ongoing challenge. This is challenging in terms of the complexity of the process in question, but also in terms of directly observing NPF by measuring sub-10 nm particle number size distributions and NPF precursor vapors. In this thesis, the standard operation procedure (SOP) for measuring sub-3 nm particle number size distributions is first defined: how to setup the instrument, maintain it, and treat and quality control the data. I also determine the best settings for running the instrument in boreal forest conditions. A second key element of this thesis is the analysis of long-term time series data. I show that in the past twenty years, the number concentration of sub-10 nm charged aerosol particles has increased in the boreal forest while total aerosol number concentration has decreased. Our results suggest that the decreasing aerosol sink can lead to increased sub-10 nm aerosol concentrations and make NPF a larger source of aerosol loading in the future. I also studied the connection between NPF precursor vapors and sub-10 nm particle number concentrations at two sites. I confirmed that sulfuric acid and highly oxygenated molecules (HOMs) can participate in NPF in the boreal forest and discovered that in Po Valley the sulfuric acid clusters are likely stabilized by bases after which HOMs participate in the growth of the particles alongside sulfuric acid and bases. Overall, this thesis focuses on improving and analyzing measurements of sub-10 nm particle number size distributions. I demonstrated that changes in the aerosol num- ber concentration can imply how atmospheric particle dynamics change in the future. Furthermore, by linking variation in sub-10 nm particle number concentrations to pre- cursor vapor concentrations, precursors relevant to NPF in a given environment are determined.

Grantor dc:publisher

Helsingin yliopisto

Year dc:date.issued

2024

Author dc:creator

• Sulo, Juha

• ilmakehätieteet

Statement dc:rights

• Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
• This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
• Publikationen är skyddad av upphovsrätten. Den får läsas och skrivas ut för personligt bruk. Användning i kommersiellt syfte är förbjuden.

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10138/569207

OAI record oai:identifier

https://helda.helsinki.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Ahelda.helsinki.fi%3A10138%2F569207