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| Hauptseite > Publikationsdatenbank > Experimental study of the chemical degradation of biogenic volatile organic compounds by atmospheric OH radicals |
| Hauptseite > Publikationsdatenbank > Experimental study of the chemical degradation of biogenic volatile organic compounds by atmospheric OH radicals |
| Book/Dissertation / PhD Thesis | FZJ-2021-03478 |
2021
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-568-0
Please use a persistent id in citations: http://hdl.handle.net/2128/28926
Abstract: Approximately 1000 Tg of carbon is annually emitted by biogenic sources. In the atmosphere, these compounds are oxidized and thereby secondary air pollutants are formed such as secondary organic aerosol (SOA) and ozone, thus contributing to air quality and climate change. At daytime, biogenic volatile organic compounds (BVOCs) are mainly degraded by photolytically produced hydroxyl (OH) radicals. In the presence of nitric oxide (NO), OH initiated reactions proceed through radical chain reactions that involve organic peroxy radicals (RO$_{2}$). In field studies conducted in forested environments, which were characterized by large BVOC emissions and low NO concentrations, measured OH concentrations were largely underestimated by model calculations using state-of-the-art chemical models, thus underestimating the oxidative capacity of the atmosphere. In the degradation scheme of isoprene, the BVOC with the globally highest emission rate, new chemical pathways for OH regeneration that involve unimolecular reactions of RO$_{2}$ have been discovered. However, few studies exist, which investigate radical regeneration in the photooxidation of other abundant hydrocarbons and monoterpenes. This thesis aims for investigating potential new pathways for radical regeneration in the photooxidation of three selected BVOCs that were abundant in previous field campaigns: 2-methyl-3-butene-2-ol (MBO), α-pinene, and the oxidation production of α-pinene, pinonaldehyde. In total, five experiments, which were conducted in 2012 and 2014 in the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber), are analyzed. A comprehensive set of instruments provided concentration measurements of OH and hydroperoxy (HO$_{2}$) radicals, OH reactivity, injected BVOCs, formed oxidation products, NO$_{x}$ (= NO + NO$_{2}$), and measurements of physical parameters (radiation, temperature, and pressure). In contrast to previous studies, all experiments were performed at ambient reactant concentrations and low NO mixing ratios (<220 pptv, parts per trillion by volume) to simulate conditions that are typical in forested regions. [...]
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