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Content archived on 2024-05-15

Origin and formation of secondary organic aerosol


Problems to be solved
Atmospheric aerosols scatter sunlight serve as condensation nuclei for cloud droplet formation and participate in heterogeneous chemical reactions. Hence, they play an important role in global climate and atmospheric chemistry. At present, the effects of aerosols are the largest uncertainties in quantifying climate forcing due to man-made changes in the composition of the atmosphere. A dominant fraction of atmospheric aerosols consists of organic substances. Few is known about sources and chemical composition of this organic fraction of atmospheric aerosols, but it is suspected to be mainly secondary organic aerosol (SOA) from natural or anthropogenic precursors. The current knowledge clearly reveals that SOA formation is prone to changes caused by anthropogenic activities, both on a global and regional scale, but a clear understanding of the processes is missing.
Scientific objectives and approach
The purpose of OSOA is to quantitatively understand the sources and formation mechanisms of secondary organic aerosols applying a combination of laboratory studies, chemical analysis of particulate matter, modelling and field observations. The laboratory experiments are specifically designed to fill existing gaps in our understanding of chemical pathways and physical processes leading to secondary organic aerosols. In order to reach that goal new analytical instrumentation and methodologies are developed. Aiming on the evaluation and validation of this laboratory work, two large field experiments are carried out. Finally, the results of both, laboratory and field work, are incorporated into atmospheric models to deliver a prognostic tool for the assessment of the SOA formation process under different environmental conditions. A combination of efforts in several fields is needed to reach the objectives of the project. The general approach of the OSOA project can be described as follows: The performance of well defined laboratory studies, including the development of new instrumental techniques, to investigate the aerosol formation from the main SOA precursors: aromatic and biogenic hydrocarbons. One main effort represents the identification of suitable particle phase tracer compounds to differentiate between the anthropogenic and the biogenic contribution to SOA. Additionally, the consortium makes use of the EUPHORE smog chamber facility in Spain. These experiments will serve as a platform to test the newly developed instruments, compare measurement strategies (QA/QC) and to perform specific experiments on reaction systems, which cannot be realised by single partners alone. Since the main objective of OSOA is the elucidation of the anthropogenic and biogenic contribution to the organic fraction of tropospheric aerosols, two field campaigns are planned to take place during the project period. The first campaign takes place in an rural area in Northern Europe (Finland) within a boreal forest, the second in a more densely populated area (Germany). At both sites, aerosol precursor measurements as well as chemical and physical characterisation of the particle phase are performed. The project contains a model development part which is of crucial importance to the overall project since it provides a link between the laboratory, outdoor simulation chamber and field work.
Expected impacts
The expected outcome of the project is highly relevant in the field of global warming and climate modelling since aerosols and their radiative properties are currently described as one of the main uncertainties in global climate models. The data received within the OSOA project will improve this situation and will finally allow a better evaluation, which actions have to be taken in the future.

Call for proposal

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EU contribution
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Bunsen-Kirchhoff Strasse 11

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Participants (9)