- Formation of secondary organic aerosol and its processing by atmospheric halogen species – A spectroscopic study (2011)
- Atmospheric aerosols play an important role in the global climate system. Through their physicochemical properties, they contribute in various ways to climate change and radiative forcing. Those properties can be considerably changed by processing the aerosols, which is especially significant for organic aerosols processed with atmospheric trace gases like halogens released through sea-salt activation or from other sources. Based on aerosol smog-chamber experiments, the formation of secondary organic aerosols (SOA) from predominantly aliphatic (α-pinene) or aromatic (catechol and guaiacol) precursors and the processing of those model SOAs with simulated molecular and naturally released halogens were studied. Different physicochemical methods were used to study the transformation of those organic aerosols. Infrared and UV/VIS spectroscopy allowed the determination of functional and structural changes during aerosol formation and processing. Using electron microscopy and measurement of the particle size distribution, the formation of the morphology and geometry of the particles was investigated. Temperature-programmed pyrolysis mass spectroscopy and ultra-high-resolution mass spectroscopy delivered detailed information on functional groups, extent of halogenation, and the macromolecular structure. Organic aerosols are significantly influenced by atmospheric halogens. Halogen species from different sources change the aerosol size distribution, the presence of functional groups, and the optical properties. Furthermore, they even form halogenated species in the solid phase of the organic aerosol.