Organics Photo-biological Transformations In Clouds – OPTIC

Transformations happening in cloud droplets are induced by light and oxidants and potentially drive atmospheric chemistry more than expected. Microorganisms have been detected in clouds and recent studies have revealed the potential importance of microbiological processes on atmospheric chemistry, since microorganisms alter the chemical composition of droplets by using dissolved organic matter (DOM) as substrate for their metabolic activity. Photochemical and biological transformations lead to a modification of the DOM composition and, consequently, to a potential variation of the properties of aerosol released after cloud evaporation. These latter are directly related, in the big picture, to the role of clouds in the radiative balance of Earth. Thus, it is essential to integrate in-cloud chemical and biological transformations with the study of climate processes, through an enhanced multidisciplinary approach.
The aim of my project is to understand the impact of microbial activity and light on cloud chemistry and, as a consequence, on the atmosphere. I will tackle this challenging problem combining field campaigns, laboratory experiments and modelling. Using high resolution mass spectrometry (FT-ICR MS), I will firstly improve the characterization of cloud water composition through analysis of samples collected in contrasted conditions. Secondly, I will evaluate the impact of microorganisms on the whole composition of DOM, through incubation of real cloud water samples and the identification of target compounds, of which I will study the biodegradation. Finally, microbial transformations will be implemented in a cloud chemistry model to study the transformations in a multiphasic environment.
We will provide exceptional insights into the cloud water composition and microbial degradations. Combined with model studies, these results will be crucial to assess the effect of microorganisms on atmospheric chemistry.