Hiukkasmuodostus ja esiastekaasut Ny-Ålesundissa, Huippuvuorilla
Year: 2025
Type: article
Abstract: Aerosols and their effects on cloud formation remain the most uncertain element contributing to the Earth's radiative balance. A considerable amount of this uncertainty is due to gaps in the understanding of the formation of secondary aerosols, a process also called new particle formation (NPF). Observational data on NPF is especially lacking in remote ecosystems, e.g. the Arctic, which is the focus area of this thesis. In NPF, vapour molecules collide and form molecular clusters, which then grow as more molecules attach to them. The compounds that can form, or contribute to the growth of, said clusters are together called precursor vapours. Precursor vapours are characterised by either having low volatility themselves, or being able to form low-volatility clusters together with other precursor gases. This group of compounds includes, for example, sulfuric acid (SA), methanesulfonic acid (MSA), iodic acid (IA), ammonia, and a group of oxidised organic species called highly oxygenated organic molecules (HOM). In this thesis, the contribution of the various precursor vapours to NPF is studied over the course of one Arctic summer, from 5th of May to the 20th of August 2024, in Ny-Ålesund, Svalbard. Ambient precursor vapour concentrations and molecular cluster compositions were studied using chemical ionisation atmospheric pressure time of flight mass spectrometer (CI-APi-TOF). Particle size distribution and NPF occurrence were monitored using a neutral cluster and air ion spectrometer (NAIS). The time series of the precursor vapour concentrations suggest that the main summertime source of MSA is the oxidation of dimethylsulfide (DMS), produced by marine phytoplankton. For SA, in addition to the DMS oxidation, long-range transport of anthropogenic sulfide seem to also contribute. Tundra vegetation appears to be the primary source for HOM at the site. A previously unidentified clustering mechanism was detected during a springtime NPF event, involving large MSA-SA-ammonia multicomponent clusters of 7-12 molecules. MSA has not before been observed to form large clusters capable of influencing NPF. Similar clusters were not detected during a summertime NPF event, but instead a large number of unidentified organics were observed at the same mass range. Also, another clustering pathway was observed, in which SA and ammonia were sequentially added to an unidentified ion core. Overall, the findings highlight the importance in studying Arctic NPF in enhancing the understanding of the climate system, both in the Arctic, and globally.
Source: Työväentutkimus Vuosikirja
Author: Vaittinen, Aarni Ilmari
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
OpenAlex ID: W7197958057