Laboratory studies of peroxy radical reactions with NOx species using turbulent flow chemical ionisation mass spectroscopy

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Bacak, A.D., 2004. Laboratory studies of peroxy radical reactions with NOx species using turbulent flow chemical ionisation mass spectroscopy. PhD, Nottingham Trent University.

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Abstract

The importance of peroxy radical reactions in the upper troposphere and lower stratosphere (UTLS) region are well known. The reaction between peroxy radicals and NOx species is a notable example, influencing as it does ozone (O3) concentrations within this region. Previous kinetic studies have been performed over small ranges of temperature and pressure and have thus been very limited. The result of these studies is a wealth of data that needs extrapolation to UTLS region parameters before it can be compared accurately with atmospheric conditions.

The main target of this work was the development of a unique analytical tool for the study of peroxy radical reactions, a chemical ionisation mass spectrometer (CIMS) turbulent flow system, capable of the detection and identification of both the reactant and product species. The system was designed and became operational. Experimental work has the focused on laboratory studies of reaction kinetics, data reported in this work representing the reactions of hydroperoxy and methylperoxy radical reactions with NO2 and the reaction between HO2 and NO over wide temperature and pressure ranges (190 - 298 K and 70 - 760 Torr).

The reaction of the hydro peroxy radical with NO was studied using the TF-CIMS system over a temperature range of 190 - 298 K at three different pressures 75, 100 and 200 Torr. The rate coefficient was found to display a negative temperature dependence, determined with Arrhenius type analysis to yield the expression k = (3.98+0.29-0.27) x 10-12 exp [(223 ± 16.5) / T] cm3 molecules-1 s-1. The rate coefficient was determined as a function of pressure, however, there was no effect of pressure on the measured rate coefficient. The product study and atmospheric implications of this reaction are discussed.

The reaction of the hydroperoxy radical with NO2 was also studied using the same system; at three different temperatures 298, 223 and 200 K over a pressure range of 150 - 700 Torr. The rate coefficient was found to be pressure dependent. For the reaction, the temperature dependent low-pressure rate coefficient can be described by the equation k0 (T) = (1.8 ± 0.3) x 10-31 (T/300)-(0.2 ± 0.3) cm6 molecule-2 s-1 and the temperature dependent high pressure rate coefficient can be described by the equation k∞ (T) = (4.7 ± 1.0) x 10-12 (T/300)-(0.5±0.3) cm3 molecule-1 s-1 The atmospheric implications of this reaction are also discussed.

The reaction of the methylperoxy radical with NO2 was also examined with the TF-CIMS system, at two different temperatures 298, 223 K over a pressure range of 100 - 700 Torr. The rate coefficient found to be pressure dependent. For the reaction, the temperature dependent low-pressure rate coefficient can be described by the equation k0 (T) = (1.5 ± 0.8) x 10-30 (T/300)-(4.0±2.0) cm6 molecule-2 s-1 and the temperature dependent high pressure rate coefficient can be described by the equation k∞ (T) = (6.5 ± 3.2) x 10-12 (T/300)-(2.0±2.0) cm3 molecule-1 s-1 The results described in this thesis are concordant with previous recommendations.

Item Type:

Thesis

Creators:

Bacak, A.D.

Date:

2004

ISBN:

9781369316667

Identifiers: