NO3 Chemistry at Night and at Sunrise - From Alkenes to Aerosols

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Freja F. Østerstrøm


DKK 850,000




Internationalisation Fellowships


Atmospheric particles contribute to air pollution and has an impact on Earth’s climate. Up to 90 % of the particles are of organic origin with a large fraction formed in atmospheric gas phase reactions. Of great interest is the formation of organic nitrates that lead to formation of secondary particles. The organic nitrates are formed in the reactions with nitrate radicals that dominate the chemistry at night and may have impact at sunrise. These reactions are associated with uncertainty and the changing conditions at sunrise has not been studied to a great extent. To understand the chemistry at the transition, I aim to characterise the atmospheric chemistry of nitrate reactions with different species under night and sunrise conditions using both experimental and theoretical methods.


The composition of atmospheric particles is a big uncertainty in understanding climate change and crucial to know in order to assess their health impacts. Understanding the drivers of the atmospheric chemistry will lead to a greater knowledge of climate change and air pollution. In this project I will investigate the reactions of nitrate radicals with different species relevant in the atmosphere, that could lead to particle formation. The impact of changing the conditions at sunrise are of interest as day and night chemistry influence each other, but previously have been studied separately. The project will add knowledge to gas phase atmospheric chemistry and particle formation as well as expand the predictive capabilities of models to be used and extended with experimental results.


I will be using two atmospheric simulation chambers to investigate the gas phase nitrate reactions to study the reactions in different chemical regimes: making it possible to study the reaction mechanisms, intermediate species, and products at molecular level up to the initial particle formation. Different instruments will be used for analysis of the data and lamps will be used to simulate sunrise in some experiments. The theoretical part of the project will be focussed on two things: simulating the experiments, describing the mechanisms of the reactions and using the experimental results to update and correct the regional and global chemical models to include the results from this study, improving predictions of particle formation used in climate predictions and air pollution forecasts.

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