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Authors: Cabrera Perez, Carlos David
Title: Simple monocyclic aromatic compounds from a global scale perspective
Online publication date: 5-Jul-2017
Year of first publication: 2017
Language: english
Abstract: In this thesis mono-cyclic aromatic compounds in the atmosphere are chemically characterized at a global scale. Atmospheric budgets, impacts on atmospheric photo-chemistry, and past and future trends of aromatic compounds are estimated using numerical simulations. The Modular ECHAM/MESSy Atmospheric Chemistry (EMAC) model with an aromatic compound oxidation mechanism was used in this thesis. Emissions from biomass burning, anthropogenic sources, and biogenic sources were incorporated, allowing us simulate sources, sinks, and mixing ratios of aromatic compounds. The model simulation was compared with a set of observations compiled from surface and aircraft measurements. We found good spatial and temporal agreement of numerically simulated concentrations of benzene; good agreement at the surface, but a large underestimation in the free troposphere for toluene, and even larger discrepancies for xylenes. The budget of most aromatic compounds is driven by anthropogenic emissions—which constitute the largest source of aromatics ( 23 TgC year−1)—as well as by photochemical decomposition, which is responsible for the removal of 27 TgC year−1 . Biomass burning is the second-largest source of aromatic compounds ( 5 TgC year−1 ), followed by the simulated chemical production of aromatics, which accounts for 5 TgC year−1 . Wet and dry deposition are responsible for a small sink of 4 TgC year−1 , and the global atmospheric burden of aromatics amounts to 0.3 TgC. A comparison of simulation scenarios including and excluding aromatic compounds revealed that they cause a net annual global mean decrease in OH and O3 mixing ratios. However, an increase in OH and O3 mixing ratios is found in the high NOx mixing ratios areas. NOx mixing ratios decreased globally due to the partial transfer of the NOx atmospheric burden into nitrogenated aromatic species. Among VOCs, glyoxal was most strongly affected by the inclusion of aromatics in the chemical mechanism, with mixing ratios increasing by 20%. Finally, we studied trends in atmospheric mixing ratios between 1950 and 2050, through a series of simulations covering past, present, and future projections. At the global scale, mixing ratios of most aromatic compounds increased steadily for the entire 100-year period, with a small decrease towards 2050. At the regional scale, the mixing ratios in Europe and North America increased from 1950 to 2010, followed by a strong decrease until 2050. In contrast, a continuous increase was found in Southeast Asia and over the Arabian Peninsula.
DDC: 500 Naturwissenschaften
500 Natural sciences and mathematics
Institution: Johannes Gutenberg-Universität Mainz
Department: MaxPlanck GraduateCenter
FB 08 Physik, Mathematik u. Informatik
Place: Mainz
URN: urn:nbn:de:hebis:77-diss-1000013996
Version: Original work
Publication type: Dissertation
License: In Copyright
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Extent: vi, 180 Seiten
Appears in collections:JGU-Publikationen

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