Daytime atmospheric chemistry of key compounds provoked by nighttime atmospheric chemistry (DARK KNIGHT).

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Sources of biogenic and anthropogenic origin emit significant amounts of volatile organic compounds (VOCs, 1300 TgC per year) into the atmosphere. After release into the atmosphere, VOCs undergo oxidation with OH and NO3 radical and O3 under formation of semi-volatile compounds that partition into the particle phase leading to the formation of secondary organic mass. Although biogenic and anthropogenic SOA is of great importance for the atmosphere (910 and 9.7 Tg per year), gaps regarding the formation mechanisms and involved compounds still exist. This is partly caused by so-far unknown formation mechanism and also due to mechanisms that lead to a reduction of SOA (like evaporation processes) and missing data sets (NO3 radical reaction). Within the first project phase, a new SOA formation mechanism has been successfully identified for anthropogenic SOA compounds due to the interconnection of day- and night time chemistry. For the present proposal, the evaporation of SOA will be examined and characterized as the existing data set clearly shows that evaporation plays an important role for nocturnal alpha-pinene SOA. Main evaporation products and the underlying mechanisms will be characterized. A second aspect for the present proposal is the data set for NO3 radical reactions of biogenic and anthropogenic VOCs. Within the first project phase, gaps in available data as well as discrepancies in existing data sets were found. The identification of the reason for these discrepancies will be investigated and a data set for the NO3 radical reaction of the most important biogenic and anthropogenic VOCs will be generated.