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A new method for size resolved chemical analysis of nucleation mode aerosol particles (size range from ~10 to ~30 nm) is presented. The Thermal Desorption Differential Mobility Analyzer (TD-DMA) uses an online, discontinuous principle. The particles are charged, a specific size is selected by differential mobility analysis and they are collected on a filament by electrostatic precipitation. Subsequently, the sampled mass is evaporated in a clean carrier gas and analyzed by a chemical ionization mass spectrometer. Gas phase measurements are performed with the same mass spectrometer during the sampling of particles. The characterization shows reproducible results, with a particle size resolution of 1.19 and the transmission efficiency for 15 nm particles being slightly above 50 %. The signal from the evaporation of a test substance can be detected starting from 0.01 ng and shows a linear response in the mass spectrometer. Instrument operation in the range of pg/m3 is demonstrated by an example measurement of 15 nm particles produced by nucleation from dimethylamine, sulfuric acid and water.
Atmospheric nanoaerosols have extensive effects on the Earth’s climate and human health. This cumulative work focuses on the development and characterization of instrumentation for measuring various parameters of atmospheric nanoaerosols, and its use to understand new particle formation from organic precursors. The principal research question is, how the chemical composition of nanoaerosol particles can be measured and how atmospheric chemistry influences aerosol processes, especially new particle formation and growth. Therefore, nanoaerosols are investigated under various aspects. More specifically, an instrument is developed to analyze nanoparticles, and field as well as chamber studies are conducted.
The main project is the instrument development of the Thermal Desorption Differential Mobility Analyzer (TD-DMA, project 1, Wagner et al. (2018)). This instrument analyzes the chemical composition of small aerosol particles. By characterization and testing in chamber experiments, it is proven to be suitable for the analysis of freshly nucleated particles.
The second project (Wagner et al. (2017)) applies a broad spectrum of aerosol measurement instruments for the characterization of aerosol particles produced by a skyscraper blasting. A comprehensive picture of the particle population emitted by the demolition is obtained.
Project 3 (K¨urten et al. (2016)) is also an ambient aerosol measurement, focusing of new particle formation in a rural area in central Germany, and the ability of a negative nitrate CI-APi-TOF to detect various substances in atmosphere. Project 4 (Heinritzi et al. (2016)) is a characterization of the negative nitrate CI-APi-TOF used in projects 1, 3, 5, 6, 7 and 8. The following projects focus on understanding new particle formation from atmospherically abundant organic precursors. Key instruments comprise the negative nitrate CI-APiTOF for gas-phase measurements of the nucleating species, and various sizing and counting instruments for quantifying the particle formation and growth. Project 5 (Kirkby et al. (2016)) shows that biogenic organic compounds formed from alpha-pinene can nucleate on their own without the influence of e.g. sulfuric acid. Project 6 (Tr¨ostl et al. (2016)) describe the subsequent growth of these particles. Project 7 (Stolzenburg et al. (2018)) covers the temperature dependence of this growth and in project 8 (Heinritzi et al. (2018)), the suppressing influence of isoprene on the new particle formation is assessed.