Gas phase ammonia is plays an important role in the formation of atmospheric aerosol particles. These particles may affect cloud properties which, in turn, modulate Earth surface temperatures and precipitation. However, the critical role of ammonia has not been unambiguously demonstrated. Underlaying challenge is that reliable ammonia measurements are extremely difficult, and little is known about concentrations, sources and fate of ammonia especially in the Arctic atmosphere. In this project, ammonia is measured using novel technology from subarctic Lapland to high Arctic Svalbard and northern Greenland. Simultaneous and diverse measurements of other relevant vapours and new particles allow us to quantify the concentrations and sources of ammonia and resolve the aerosol particle formation mechanisms. Arctic climate and environment are changing fast. Resolving the role of ammonia in Arctic climate system helps understanding the present and predicting the future climate.
We are part of the Center of Excellence in research funded by the Research Council of Finland during 2022-2029. Our work is in the experimental part of the project, providing new insight on topics "Eliminating detection biases" and "Measuring the chemical composition of clusters and nanoparticles".
The EU-funded PACIFIC project will test a wide range of SAFs with consistent engine settings and fuel compositions. The project will improve models for soot formation, predict particle emissions more accurately, and assess SAF’s potential. This will support the development of sustainable aviation practices.
Project 2025-2028
Aviation affects our climate in complex ways. UNIC (Understanding the Non-CO₂ Impacts of DeCarbonised Aviation) will address key knowledge gaps to enable both science and policy to tackle them. UNIC combines innovative in-flight and ground-based emissions measurement methods, advanced lab-scale experiments, and cutting-edge modelling.
Project 2025-2029
The relative importance of biogenic aerosol production as a forcing component will increase in
future as anthropogenic aerosol emissions will decrease when fossil fuel-based energy production
is replaced by fossil free solutions. Our objective is to assess the biogenic aerosol production
potential of Danish afforestation actions by performing measurements, which will form
the basis for estimating biogenic aerosol emissions, and further the cooling by aerosol-cloud interactions
at regional scale. These are the first comprehensive measurements to quantify natural
aerosol production in a Danish forested environment.
Intensive measurement campaign at old forest site (Sorø) in 2026-2027
We have started measurements of condensable vapors and aerosols in India with co-operation with IIT Delhi.
Project in 2026
New particle formation describes a certain process where tiny particles are formed out of vapour molecules in the atmosphere. Those newly formed particles – or molecular clusters with sizes around 1-3 nanometers – can grow to sizes of cloud condensation nuclei (> 50 nanometers) and influence the optical properties, lifetime and precipitation of clouds, thereby connecting new particle formation to Earth’s radiative balance and climate. Approximately half of all cloud condensation nuclei in the air are formed through this process. Since these particles in the air have massive influence on climate it is crucial to understand their formation processes in different atmospheric environments in detail. This is our main research challenge, and this is why we carry our detector complexes around the globe.
In the gas-phase, little clusters form through reactions of different vapours. Compounds such as sulphuric acid and ammonia can in proper conditions stick to each other and form the initial seeds of new particles. However, there are likely several mechanisms via which new clusters are formed in the different parts of the Earths atmosphere. These mechanisms are only vaguely understood. Recently, we succeeded to resolve the cluster formation mechanism in the coastal environment where iodic acid was found the be responsible on cluster formation.
To have any climatic relevance, tiny clusters need to grow to sizes above some 50 nanometers. Vapours like sulphuric acid or extremely low volatile organic compounds are needed to ensure this growth, otherwise the little clusters would just “stick” to coarse particles in the atmosphere and “disappear”. Still not all vapours could have been identified through measurement campaigns. In our group, we investigate the new particle formation in different areas and climate zones around the globe to detect all gases involved.
With understanding the new particle formation, we are able to understand also the influence of human activities on the process. Our experimental results can be used to improve the predictive power of e.g. global climate models.
Besides understanding the mechanisms of cluster and new particle formation, it is also crucial to understand the chemical reactions leading to production of the cluster / particle precursor vapours. Hydroxyl radical (OH) is an important oxidant, but our recent research have pointed out some previously disregarded or unknown chemical reaction pathways crucial for understanding the precursor formation. These include the reaction of so called stabilised Criegee intermediates with sulphur dioxide leading to sulphuric acid production as well as so called auto-oxidation reaction, producing extremely low volatile organic compounds. Still, yet unknown mechanisms are needed to explain e.g. the atmospheric formation of iodic acid.
Why resolving the chemistry and physics related to cluster formation is so difficult? Why we still have open questions? It’s because the concentrations of particle precursor vapours and clusters are so small that it is challenging to analyse. Sulphuric acid, for example can be important for particle formation at the concentrations of 1 ppq (part per quadrillion). It means, that out of 10^15 (1 million billions) molecules of atmospheric air only 1 molecule would be sulphuric acid. Imagine a human hair. It’s diameter, ~100 micrometers, is ~1 ppq of the distance between the earth and sun. So it’s hard! And harder it gets when we want to detect clusters and their chemical composition. Their concentrations are namely still lower.
If the detector technology would have been on required level, all our research questions would have been answered already. But that has not been the case. Because of the challenge that the extremely low concentrations of clusters and precursor vapours create, one of the cornerstones of our research is continuous instrument and method development toward increasing sensitivity and identification capability. Some of the detection technologies we have been working with have also been commercialised via spin-off companies. Airmodus Ltd., for example, manufactures and distributes chemical ionisation sources while Karsa Ltd. develops and manufactures mass spectrometer systems for aviation security applications. Both technologies have emerged from the basic research we have been conducting within last decade.
Quantitative high-quality data
In order to study the precursors and growth of the particles we have to have quantitative methods to study them. Whereas to understand the trends and changes happening in the atmosphere we have to have long-term measurements of the atmospheric vapors and particles. ACTRIS CiGas-UHEL is a topical center hosted by University of Helsinki with a key-mission to offer operational support for continuous long-term measurements of condensable vapours and aerosol precursors such as sulphuric acid and oxidized organic compounds in the atmosphere. The core activity of CiGas-UHEL is to ensure sustainable and traceable high-quality data and data products of in-situ measured atmospheric reactive trace gases with known uncertainty. That is accomplished by: