Periodic Reporting for period 2 - MaSMob-Lion (Mass-Mobility-Size for light ions/clusters)
Berichtszeitraum: 2022-09-01 bis 2023-08-31
The MaSMob-Lion project investigates the mass, size, and electrical mobility relation of light ions and clusters in gas. By measuring experimentally the mobility and mass of ions with known structures using a Planar Differential Mobility Analyser coupled with a Time-of-Flight Mass Spectrometer (DMA-MS, Figure 1), high quality data are collected in nitrogen and air under different temperature and humidity conditions. These data provide insights in studying how ion mobility respond to temperature and humidity changes as well as to carrier gas and ion conformation. Through the effective diameter approach, the measured mass-mobility relation is further linked to ion size in the free molecular regime. The derived parameters are comparable to the derivation using coefficients suggested in the ISO15900. The temperature, humidity and structure dependence of the mass-mobility relation is parameterised. However, due to possible solvation/oxidation in dry conditions and limitation in the generalisation of the parameterisations, a reliable model cannot be formulated yet. Further experiments with ions of more diverse functional groups and structures are necessary to be carried out with better control over the ionisation, especially in dry conditions.
In addition, this project also explores how particle activation diameter measured by supersaturation-based instruments, e.g. a Particle Size Magnifier (PSM), is related to the ion mass and mobility. The experimental results suggest that for monomer ions, the initial diethylene glycol (DEG) attachment is likely site dependent, and water assists in this process. Although the project has ended officially on August 31, 2023, further investigations on the initial DEG attachment and the role of water are continued in collaboration with modellers.
In general, the overall outcomes of the project meet the objectives, in spite of delays and technical difficulties. The work carried out in the project points at the necessities of improvement in future experimental design and provides a means towards the formulation of a model for mass-mobility-size conversion.
In addition, this project also explores how particle activation diameter measured by supersaturation-based instruments, e.g. a Particle Size Magnifier (PSM), is related to the ion mass and mobility. The experimental results suggest that for monomer ions, the initial diethylene glycol (DEG) attachment is likely site dependent, and water assists in this process. Although the project has ended officially on August 31, 2023, further investigations on the initial DEG attachment and the role of water are continued in collaboration with modellers.
In general, the overall outcomes of the project meet the objectives, in spite of delays and technical difficulties. The work carried out in the project points at the necessities of improvement in future experimental design and provides a means towards the formulation of a model for mass-mobility-size conversion.
The MaSMob-Lion project started on Aug. 1, 2021 and lasts through Aug. 31, 2023, in total 25 months. The outgoing phase (Aug. 1, 2021-Aug. 31, 2022) was carried out in the partner organisation, Indiana University–Purdue University Indianapolis (IUPUI) in the United States, under the supervision of Prof. Carlos Larriba. Mobility and mass data have been collected for altogether 40 ions, including amino acids and ammonium ions and clusters. Ammonium samples were analysed in positive mode and amino acid samples were analysed in both positive and negative polarities under nitrogen and air for 0%, 20% and 40% humidity at 24 oC, 34 oC and 41 oC. In the return phase, further experiments on mobility-mass measurements were carried out in the University of Helsinki in collaboration with Dr. Juha Kangasluoma, where one more temperature condition (14 °C) was achieved. Measurements of a series of alkylammonium ions were also performed at the return host, the University of Tartu. Data collected during both outgoing and return phases have been processed and a manuscript is to be submitted.
The project results have been presented at four conferences: American Association for Aerosol Research (AAAR 40th Annual Conference, Oct. 18-22, 2021, oral), 70th American Society for Mass Spectrometry (ASMS2022, June 5-9, 2022, poster), 11th International Aerosol Conference (IAC2022, Sept. 4-9, 2022, oral) and European Aerosol Conference (EAC) 2023 (Sept. 2-8, oral); and at one workshop: 23rd Finnish-Estonian Air Ion and Aerosol Workshop (May 29-30, 2023, oral). In addition, the ER has established collaborations with researchers from Aarhus University, University of Minnesota and University of Helsinki in performing quantum chemistry calculations of the studied ion systems and interpreting the results. The ER has also seconded in Airmodus Oy in Helsinki Finland. During the secondment, in addition to learning practices in company production and R&D work, the ER performed measurements on a DMA-MS setup coupled with a PSM in collaboration with Dr. Juha Kangasluoma et al. from the University of Helsinki.
Performed work:
- Mobility-mass measurements under different temperature and humidity conditions in air and nitrogen (outgoing and return phases)
- Characterisation of the dependence of the mass-mobility relation on ion structure, T, RH and the influence of polarisation (outgoing and return phases).
- Parameterisation using the effective diameter approach and comparison with derivation using coefficients suggested in the ISO15900 (return phase).
- Measurement of activation diameter together with mass-mobility data (secondment&return phase).
- Investigation of the supersaturation needed for activation in relation to the ion structure and mass (return phase).
The project results have been presented at four conferences: American Association for Aerosol Research (AAAR 40th Annual Conference, Oct. 18-22, 2021, oral), 70th American Society for Mass Spectrometry (ASMS2022, June 5-9, 2022, poster), 11th International Aerosol Conference (IAC2022, Sept. 4-9, 2022, oral) and European Aerosol Conference (EAC) 2023 (Sept. 2-8, oral); and at one workshop: 23rd Finnish-Estonian Air Ion and Aerosol Workshop (May 29-30, 2023, oral). In addition, the ER has established collaborations with researchers from Aarhus University, University of Minnesota and University of Helsinki in performing quantum chemistry calculations of the studied ion systems and interpreting the results. The ER has also seconded in Airmodus Oy in Helsinki Finland. During the secondment, in addition to learning practices in company production and R&D work, the ER performed measurements on a DMA-MS setup coupled with a PSM in collaboration with Dr. Juha Kangasluoma et al. from the University of Helsinki.
Performed work:
- Mobility-mass measurements under different temperature and humidity conditions in air and nitrogen (outgoing and return phases)
- Characterisation of the dependence of the mass-mobility relation on ion structure, T, RH and the influence of polarisation (outgoing and return phases).
- Parameterisation using the effective diameter approach and comparison with derivation using coefficients suggested in the ISO15900 (return phase).
- Measurement of activation diameter together with mass-mobility data (secondment&return phase).
- Investigation of the supersaturation needed for activation in relation to the ion structure and mass (return phase).
The project results assist mass-size-mobility interconversion, which are essential in studying ions and aerosol particles, whereby potentially benefiting the investigation of atmospheric new particle formation and the improvement of the understanding of cloud and air pollution formation from secondary aerosol particles. The results can also possibly find applications in engineering aerosol particle production and pharmaceutical development.
• Scientifically
- Mass-mobility data under different atmospheric-relevant T and RH valuable to be added to database for future comparisons.
- Solvation/oxidation of small ions in dry condition pointing at cautions in future experimental design and result interpretation of mobility measurements under atmospheric pressure.
- An approach to parameterize T, RH and structure effects as well as polarization in mass-mobility relation using the effective diameter method.
- Model applicability is limited when derived without diverse chemical structures and functional groups in the parameterization.
- Site preference over mass in the initial DEG attachment to small monomer ions.
- Water able to lower the supersaturation needed for particle activation in PSM, i.e. water assists DEG attachment.
- Necessary to improve ambient data interpretation regarding the humidity effect.
• Technologically
- Method to control and monitor T and RH in mobility measurements.
- Integration of a PSM in parallel to mass spectrometry downstream of mobility measurements.
- RH control and monitoring to PSM calibration setup.
Socially and Economically, the project results are valuable in helping better interpret ion mobility, mass and size properties. For example, the study on the mobility-mass-size relation helps the intercomparison of ambient aerosol and ion data measured by different techniques, and the work on RH effect in particle activation in PSM is potentially useful in developing methodology to take the RH effect into consideration when analysing and comparing ambient data. These results benefit the elucidation of atmospheric new particle formation and thereby characterising climate impacts of secondary aerosols and their role in air pollution. An improved understanding of aerosol climate impacts and their involvement in air pollution provides a foundation for assessment of the impact of anthropogenic emissions and assists the development of emission reduction strategy.
• Scientifically
- Mass-mobility data under different atmospheric-relevant T and RH valuable to be added to database for future comparisons.
- Solvation/oxidation of small ions in dry condition pointing at cautions in future experimental design and result interpretation of mobility measurements under atmospheric pressure.
- An approach to parameterize T, RH and structure effects as well as polarization in mass-mobility relation using the effective diameter method.
- Model applicability is limited when derived without diverse chemical structures and functional groups in the parameterization.
- Site preference over mass in the initial DEG attachment to small monomer ions.
- Water able to lower the supersaturation needed for particle activation in PSM, i.e. water assists DEG attachment.
- Necessary to improve ambient data interpretation regarding the humidity effect.
• Technologically
- Method to control and monitor T and RH in mobility measurements.
- Integration of a PSM in parallel to mass spectrometry downstream of mobility measurements.
- RH control and monitoring to PSM calibration setup.
Socially and Economically, the project results are valuable in helping better interpret ion mobility, mass and size properties. For example, the study on the mobility-mass-size relation helps the intercomparison of ambient aerosol and ion data measured by different techniques, and the work on RH effect in particle activation in PSM is potentially useful in developing methodology to take the RH effect into consideration when analysing and comparing ambient data. These results benefit the elucidation of atmospheric new particle formation and thereby characterising climate impacts of secondary aerosols and their role in air pollution. An improved understanding of aerosol climate impacts and their involvement in air pollution provides a foundation for assessment of the impact of anthropogenic emissions and assists the development of emission reduction strategy.