Atmospheric Biogenic Sugars – ABS

Primary biogenic organic aerosol (PBOA) is little studied although it forms up to 30% of the organic fraction of atmospheric PM (in Europe in summer average) and presents important properties for atmospheric particles (PM), both for cloud formation and for health impacts. Despite its importance, this fraction is currently not considered in atmospheric chemistry models. Current studies are generally limited in time, space, or range of species measured, which does not allow for a reliable assessment of emission sources and processes.

ABS proposes to establish a more comprehensive study of this primary biogenic contribution to PM, and particularly to its organic fraction, in different types of environments, to specify the main emission sources, and to determine whether this contribution has varied significantly over the last 150 years. One of the barriers to such studies is the analytical limitation for the chemical species included in this fraction (sugars and sugar alcohols), which ABS will overcome by developing an innovative LC-MS/MS method at low concentration of about thirty of these species in mixture. ABS will study this fraction via these chemical measurements in association with the microbiology of the samples, including abundance and genomic analyses of the microbial and fungal diversity. The central hypothesis of the project is that an important part of these species is closely related to living matter (bacteria and fungi), and that the coupling of chemical and microbiological measurements can lead to a better understanding of their sources and emission processes to the atmosphere, as well as of the interactions between chemistry and microbiology in situ.

We will consider the variability and sources of this chemical fraction in PM series collected mainly in Europe but also in tropical areas (e.g. 1500 samples), in the seasonal alpine snowpack and in an alpine ice core corresponding to a 150-year record (Col du Dome, Mont Blanc). The snowpack work will include both in situ and mesocosm studies to understand the biological processes involving these carbohydrates in cold snow, including potential changes in the chemical profiles of sugars in the deposits. Atmospheric and ice samples constitute a unique collection and are already analyzed for a wide range of chemical properties and tracers, the original combination of which will allow source apportionment by advanced methods such as Positive Matrix Factorization, methods that will be applied with this magnitude for the first time on an ice core. The simultaneous treatment of samples in the 3 environments will give access to essential information on the transfer processes that are necessary for the interpretation of ice core records.

ABS will be totally innovative for the 3 fields, atmospheric geochemistry and microbiology, and glaciology. The synergy of the approach in the 3 domains will reinforce these advances with a unique view of the importance of atmospheric PBAO emissions and concentrations, coupling with living matter, and their historical evolution in the European atmosphere. ABS should reinforce the strong need to take into account these primary biogenic emissions in atmospheric chemistry models. The advances in the knowledge of the emission sources by ABS will open the door to the quantification of the specific processes involved for further emissions inventories. The established proof of concept of using these species in ice cores as tracers of the evolution of particulate biogenic composition will allow applications to other glaciological records, in mid latitudes and polar ice.