Airborne microalgae: investigating their aerosolization potential and gaseous emissions

Atmospheric aerosols influence the Earth’s radiation balance and play a significant role in cloud formation, as well as air quality. Among biological aerosols, there is a clear lack of understanding the impact airborne microalgae have on climate.  To date, most studies have focussed on the associated health and environmental effects when microalgae disperse to new environments; their interactions with sunlight and potential role in cloud seeding have so far been largely neglected.

In this work, we performed detailed laboratory measurements to mimic the potential release of microalgae from the oceans into the atmosphere.  For this purpose, we utilized a sea spray simulation chamber with a plunging jet. We selected microalgae strains from saltwater and freshwater environments that have previously been found to be important for the release of dimethyl sulphide, a compound that is imperative for new particle formation in the atmosphere in marine regions. We focussed on the investigation of the emission of the microalgae themselves and volatile organic compounds (VOCs) that are simultaneously released. Aerosol particle concentrations and size distributions were tracked online by using an aerosol size spectrometer; additionally, the emitted particles were sampled with an impinger and counted using microscopy. A proton-transfer-reaction mass spectrometer continuously measured the VOCs, which were also periodically sampled with Tenex sorbent tubes and analysed using mass spectrometry. Furthermore, we analysed whether microalgae viability was affected by the water-air transfer.