How does vapour generate climate-cooling particles?

Mikael Ehn has received seven-figure funding from the EU to continue his research into atmospheric vapours.

The air around us is composed of more than gas – there are solid and liquid particles floating around as well. Aerosol particles are known to cool the atmosphere.

The formation and dynamics of organic particles is not yet well known, so their inclusion into atmospheric modelling has been difficult.

“Funded by the European Research Council, my COALA project seeks to describe organic particles in a completely new way. We’re using the latest mass spectrometry technology,” explains University Lecturer Mikael Ehn from the University of Helsinki’s Department of Physics.

Will the compound evaporate or condense?

All compounds that wind up in the atmosphere have a specific level of volatility, or vapour pressure. Volatile compounds remain gaseous, while those with low vapour pressure are unlikely to evaporate and more likely to become condensed into particles.

Thus, the generation of organic aerosols in the atmosphere can be explained either by a small amount of a low-volatility compound or a large amount of a high-volatility one.

“Determining the distribution of different evaporation rates is one of the key goals of the COALA project. Previously this would have been impossible, as the required measuring equipment did not exist,” explains Ehn.

The vapours that create particles are generated both in nature and through human action.

First came the measuring equipment

Some of the equipment used in the project has been developed at the University of Helsinki’s Division of Atmospheric Sciences led by Academy of Finland Research Fellow Markku Kulmala at the Department of Physics.

Measurements will be taken simultaneously using several separate mass spectrometers, each of which has its own group of compounds to measure. “There still isn't one single instrument that could take all these measurements simultaneously. This is why we need such an extensive arsenal of instruments, which is very difficult to find. But Kulmala’s group has it,” Ehn states.

“We will first apply the measurement results to chemical process models, then to regional models and finally to models on the global scale,” Ehn explains. A regional model can be a simulation of reactions occurring over a conifer forest, for example.

The goal of the five-year project is to better understand the generation, evolution and life-cycle of organic particles in the atmosphere. “We need models to simulate the particles of the atmosphere in history, currently and in the future."

Aerosols, butterflies and philosophy

Ehn's project has received five years of funding from the EU. Thus far, two other University of Helsinki researchers have received the same Starting Grant from the 2014 application round: Marjo Saastamoinen for her butterfly research and philosopher Jose Pereira da Silva from the Helsinki Collegium for Advanced Studies.

More ERC grant decisions will be made this winter. The next grants to be decided by the ERC will be the Consolidator Grants and the Advanced Grants.