Further specification of water-soluble brown carbon in aerosol particles (BranKo II)

• Applicant: Dr. Dominik van Pinxteren
• Subject Area: Atmospheric Science
• Term: from 2013 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 248903411

The DFG project BranKo (Specification of water-soluble brown carbon in aerosol particles) studied concentrations and sources of several light-absorbing organic substances (so-called brown carbon, BrC) in atmospheric aerosol particles. Among others, imidazoles were in the focus of these studies, as these species are known i) to have a potential impact on the Earth radiative balance by absorbing visible light, and ii) to trigger chemical reactions in the atmsophere by photosensibilisation. The impact of imidazoles on such processes has so far only been studied in laboratory experiments. BranKo, for the first time, delivered data on ambient concentrations for several sites in different atmospheric regimes. The data set, however, is still limited in size, making statistically robust conclusions on typical concentration ranges and potential sources difficult. Therefore, the follow-up project BranKo II aims at extending the data on ambient imidazole concentrations for a number of different sites, allowing for more detailed insights. From the preliminary BranKo results, biomass burning likely is an important source of imidazoles in the atmosphere. The field data did not, however, allow conclusions on their emission and/or formation pathways. Imidazoles could form directly upon combustion, i.e. be primarily emitted into the atmosphere, and/or they could form in secondary processes from precursor gases during the transport and ageing of the smoke plume, as suggested from laboratory studies. Understanding the importance of each of these two processes is a second major goal of BranKo II. It will be addressed in controlled experiments in a biomass burning smog chamber, which allow the discrimination of primary emission from secondary processes.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Hartmut Herrmann