Effect of NH₃on the formation of indoor secondary organic aerosols from monoterpene/ozone reactions

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Effect of NH₃on the formation of indoor secondary organic aerosols from monoterpene/ozone reactions


Author: Niu, Xinyi
Title: Effect of NH₃on the formation of indoor secondary organic aerosols from monoterpene/ozone reactions
Degree: M.Sc.
Year: 2013
Subject: Cleaning compounds -- Environmental aspects.
Indoor air quality.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Construction and Environment
Pages: ix, 82 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2646927
URI: http://theses.lib.polyu.edu.hk/handle/200/7175
Abstract: Monoterpene as the most commonly Biogenic volatile organic compounds (BVOCs) in cleaning products and air fresheners are unsaturated and very reactive, which can react rapidly with indoor oxidants such as ozone (O₃) to produce secondary organic aerosols (SOAs) in indoor environments, and the reactions can be influenced by indoor gaseous pollutants such as ammonia (NH₃). So it is important to characterize the formation of SOAs and to investigate the effect of NH₃ on the monoterpene and ozone reaction, and the surface compositions and carbon compounds were also indicated. This study focuses on ozone-initiated formation of indoor secondary organic aerosols (SOAs) with monoterpene in a large environmental chamber. Experiments were done with and without the presence of NH₃. The results demonstrated that the presence of NH₃ can significantly enhance SOAs formation in the ozonolysis of monoterpene. The maximum total particle concentration was up to 1.4×10⁵ #cm⁻³ in the presence of NH₃, while it was 5.7×10⁴ #cm⁻³ without NH₃, which was 60% lower. The nuclei coagulation and condensation resulted in the growth of SOAs, and it was found that the presence of NH3 slightly enlarges the mean particle diameter. In order to have further knowledge of the SOAs, we used X-ray photoelectron spectroscopy (XPS) to characterize the surface properties of SOAs from ozone and monoterpene reactions with and without the presence of NH3. The different elements O, C, N and associated core energy levels are indicated in the spectrums. The decreasing O/C ratio indicated there were a mass of new organic matters containing carbon generated. The increasing N/C ratio indicated the larger amount of nitrogen-containing organic compounds with the presence of NH₃, and the main components are cyanide and organic matrix. Among the four types of carbon contents: unsubstituted aromatic carbon (C-C/C-H); aliphatic carbon (C-C/C-H); amide carbon (C(O)N) and carboxylic carbon (C(O)O), C-H was the main carbon structure which occupied over 60% of the carbon-containing compounds. With the presence of NH₃, there were more C-N and COO functional groups generated in the ozone and monoterpene reactions. Results obtained in this study will not only improve our understanding of the effect of NH₃ on the formation of ozone-derived SOAs and the surface properties of SOAs, but also raise the awareness of public that the importance of improving indoor air quality.

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