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@PHDTHESIS{Karl:41885,
author = {Karl, Matthias},
title = {{M}odellierung atmosphärisch-chemischer {R}eaktionen in
der {T}ageslicht-{A}tmosphären-{S}imulationskammer},
volume = {4140},
issn = {0944-2952},
school = {Univ. Münster},
type = {Dr. (Univ.)},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-41885, Juel-4140},
series = {Berichte des Forschungszentrums Jülich},
pages = {215 S.},
year = {2004},
note = {Record converted from VDB: 12.11.2012; Münster, Univ.,
Diss., 2004},
abstract = {The abundance of the higly reactive hydroxyl radical (OH
radical) in the troposphere (lower 10 kilometers of the
atmosphere) is of great importance for the removal of both
naturally occurring trace gases and those brought in by
human activities. Ozone (O$_{3}$) is formed in a complex
reaction sequence during the OH-induced degradation of
volatile organic compounds (VOC) involving nitrogen oxides
(NO$_{x}$, NO$_{x}$ = NO + NO$_{2}$) and solar radiation.
Elevated levels of ozone mixing ratios in the planetary
boundary layer (lower up to two kilometers of the
troposphere) represent a serious hazard for human health and
vegetation. Isoprene, a volatile organic compound released
by vegetation, plays an important role in the formation of
ozone. Its high reactivity towards the OH radical in
conjunction with its large global emission rate renders
isoprene a compound of outstanding importance in the
atmosphere. Formaldehyde (HCHO) is a major product from
isoprene oxidation and represents a substantial source for
HOx radicals (combined OH radicals and hydrogen peroxy
radicals (HO$_{2}$)). The atmosphere simulation chamber
SAPHIR provides the opportunity to investigate different air
masses with defined chemical compositions under conditions
(sun light, temperature and pressure) comparable to the
atmosphere. An important advantage of SAPHIR is the
possibility to study kinetic parameters (for example rate
constants) from the gas-phase oxidation of VOC at
tropospheric mixing ratios of reactants. The method of
sensitivity analysis is employed to develop an experimental
design for chamber experiments exploring rate constants in
SAPHIR. Chamber sources for gaseous nitrous acid (HONO) and
HCHO can have a strong impact on gas-phase chemistry.
Parameterisations for these chamber sources were derived
from the measured temporal increase of the respective
compounds. Time dependent concentration profiles of HCHO
from chamber experiments investigating the photochemical
removal of HCHO were analysed. Analysis of the chemical
balance of HCHO supplied evidence for the correctness of the
spectralradiometric method used for the determination of
photolysis frequencies of HCHO. The rate constant of HCHO
with the OH radical, determined in this work, is within the
error limits of the actually recommended value. Based on a
current chemical sheme for the degradation of isoprene,
which embodies recent kinetic data and reaction pathways, a
detailed pattern for the treatment of the isoprene oxidation
products methacrolein (MACR) and methyl vinyl ketone (MVK)
was developed. In experiments investigating the OH-induced
and O$_{3}$-induced oxidation, rate constants were
determined for the initial steps, using measured
concentrations of isoprene, OH and O$_{3}$. The determined
values are in accordance with literature values. In
comparison with literature values of OH-induced oxidation of
isoprene in the presence of NO$_{x}$, higher product yields
were derived for MACR and MVK, while the rate constants of
their OH-reactions were lower for about 20 \%. The
tropospheric relevance of these results was investigated
using a photochemical scenario which represents a polluted
air mass over a close-to-the-city forest area. It was
concluded that MACR and MVK provide an important sink for OH
radicals.},
cin = {ICG-II},
cid = {I:(DE-Juel1)VDB48},
pnm = {Chemie und Dynamik der Geo-Biosphäre},
pid = {G:(DE-Juel1)FUEK257},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/41885},
}