Quantifying the OH radical by global scale NMHC measurements from the NOAA-ESRL cooperative flask sampling network [Elektronische Ressource] / Jan Pollmann

Pollmann

Sujets

• Social work

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2007
• Nombre de lectures: 71
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Quantifying the OH radical by global scale
NMHC measurements from the
NOAA – ESRL cooperative
flask sampling network


Dissertation zur Erlangung des Grades
“Doktor der Naturwissenschaften”


Am Fachbereich: Chemie, Pharmazie und Geowissenschaften
der Johannes Gutenberg – Universität in Mainz


Jan Pollmann

geboren am 29.März 1978 in Osnabrück


Mainz den 25.6.2007 2
Table of Contents:

1 Introduction 5

1.1 Non-methane hydrocarbons in the atmosphere 6
1.1.1 Sources 6
1.1.2 Global distribution of NMHC 7
1.2 Atmospheric Oxidation Chemistry 9
1.2.1 Hydroxyl radical chemistry 9
1.2.2 OH Distribution 11
1.2.3 Other oxidative reactions (nitrate, ozone, halogens) 12
1.3 NOAA – ESRL cooperative air sampling network 14
1.4 Variability Analysis 16
1.5 Thesis Outline 21

2 Evaluation of Adsorbent Materials for Cryogen – Free Trapping –
GC Analysis of Atmospheric C2 – C6 NMHC 24

2.1 Introduction 25
2.2 Instrumental 28
2.3 Experiments 33
2.3.1 Adsorbent Material Evaluation 33
2.3.2 Interference from water vapor 34
2.4 Results and Discussion 34
2.4.1 Adsorbent Material Evaluation 34
2.4.2 Interference from water vapor 48
2.5 Conclusions and implications for microtrap
thermodesorption applications 50
2.6 Acknowledgements 51 3
3 Sampling of Atmospheric Sesquiterpenes: Sampling Losses and
Mitigation of Ozone Interference 52

3.1 Introduction 53
3.2 Experiments 56
3.3 Results and Discussion 60
3.3.1 SQT losses in the presence of ozone 60
3.3.2 Ozone mitigation techniques 67
3.4 Implications for research on sesquiterpene flux studies 78
3.5 Acknowledgements 80

4 Sampling, Storage and, Analysis of C2 – C7 Non – Methane
Hydrocarbons from Whole Air Glass Sampling Flasks 81

4.1 Introduction 82
4.2 Instrumental 86
4.3 Experiments 92
4.3.1 Sampling method validation 92
4.3.2 Calibration, accuracy, and precision 94
4.4 Results and Discussion 96
4.4.1 Sampling method validation 96
4.4.2 Calibration, accuracy, and precision 100
4.5 Conclusions 117
4.6 Acknowledgements 118 4
5 Global NMHC Measurements from the NOAA – ASRL Cooperative
Air Sampling Network: observations and Assessment of OH
Concentration by Variability 119

5.1 Introduction 121
5.2 Experiments 125
5.3 Results and Discussions 130
5.3.1 Individual Stations 130
5.3.2 Global Distribution 139
5.3.3 OH quantification by variability analysis 145
5.4 Conclusions 154
5.5 Acknowledgements 155

6 Conclusions and future perspectives 156

7 Summary 161

8 Bibliography 165 5
1 Introduction

The overall aim of this thesis is to improve our understanding of the global
distribution of non-methane hydrocarbons (NMHC) in the atmosphere and study
implications for the global oxidation chemistry. Particular emphasis is placed on assessing
the global distribution of the main atmospheric oxidant: the hydroxyl radical (OH). This work
focuses on reactive, non-oxygenated C2-C7 atmospheric NMHC. These compounds can
yield insight into various atmospheric processes such as transport, source structure and
oxidative chemistry. However, the global meridionally varying background distribution of
most NMHC has been largely unknown. Therefore, the scientific understanding of the
earth’s atmosphere can be significantly enhanced by the knowledge of the global
distribution of the most important NMHC.
In this section we present a detailed overview of the current knowledge on
atmospheric trace gases relevant to this thesis. The main sources of anthropogenic volatile
organic compounds to the atmosphere are presented. We then describe the main
atmospheric oxidation mechanisms and their implication for the NMHC budget.
Furthermore, we describe the NOAA cooperative air sampling network which provided us
with the air samples. Subsequently, a novel technique, based on the variability lifetime-
relationship to estimate the 24 h average OH mixing ratio an air sample was exposed to
during transport, is presented. Finally, the specific research aims and the outline of this
thesis are detailed.

6
1.1 Non-methane hydrocarbons in the atmosphere

1.1.1 Sources
The natural to anthropogenic emission ratio for NMHC to the atmosphere was
estimated to be approximately 2 (van Aardenne et al., 2001). However, biogenic emissions
were mostly characterized by unsaturated, highly reactive species with lifetimes on the
order of a couple hours (Guenther et al., 1999). Therefore, these species mostly have local
effects on atmospheric chemistry. Anthropogenic NMHC emissions are usually dominated
by saturated short-chained compounds with lifetimes on the order of several days (hexane)
to months (ethane) (Atkinson, 1994). These species can impact atmospheric chemistry on
a regional to hemispheric scale. The following sections will exclusively focus on the
atmospheric chemistry of the long-lived anthropogenic C2-C7 organic trace gases since
one of the primary scientific aims of this thesis is to determine the global distribution of
these compounds.
The global anthropogenic non-methane hydrocarbon (NMHC) emissions to the
atmosphere are dominated by fossil fuel usage, notably their evaporative loss and
incomplete combustion. Natural and technical combustion processes such as internal
combustion engines or furnaces are always incomplete to a certain degree. Reasons may
include the lack of oxygen, low combustion temperatures or the residence time in the
burning zone being too short. Minor emissions develop from fossil fuel exploitation and
production, biofuel use as well as from anthropogenic biomass burning, the latter
considering that most fires are human-induced (Singh et al., 2000). However, these minor
processes may dominate the source structure of atmospheric NMHC in remote regions. A
brief summary of NMHC emission sources to the atmosphere is shown in table 1.1. The
main source regions for anthropogenic NMHC emissions are located in the mid-northern
latitude region (30-60 °N) as the vast majority of industrialized countries are located. The
emissions in this region are dominated by incomplete combustion of fossil fuels. Significant
NMHC emissions from fossil fuel exploitation can be expected in the Arctic region as well
as near the latitudinal region of the Tropic of Cancer (23.5 °N). Large biomass burning
emissions periodically occur in the Arctic regions (Siberia, Canada and Alaska) as well as
in tropical regions and Australia (Riano et al., 2007). Biofuel burning for energy production 7
becomes an important emission source for the developing countries mostly located south
of the Tropic of Cancer. The dominant sink for all these species is reaction with the
hydroxyl radical and is detailed in a later section.

Table 1.1: anthropogenic NMHC emission sources to the atmosphere
Compounds Source Reference
Acetylene and ethene biomass burning Singh et al., 2000
Acetylene flaming combustion Blake et al., 1996
C2-C5 alkanes flare emissions Kim et al., 2005
Ethane natural gas cobustion Na and Kim, 2001
Ethane biofuel burning Bertschi et al., 2003b
Ethane, propene residual smoldering combustion Bertschi et al., 2003a
Ethane, propane leakage liquefied petroleum gas Sahu and Lal, 2006
Ethane, propane gas leakage Yang et al., 2005
Ethane, propane refinery Kim et al., 2005
C2-C5 NMHC motor vehicle exhaust Kim et al., 2005
Ethene and 1,3-butadiene fresh biomass burning plumes Blake et al., 1996
Propane fossil fuel production Olivier et al., 1996
Propane smoldering combustion Blake et al., 1996
Propane biomass burning Gros et al., 2003, 2004
Propane, butane natural gas burning Mugica et al., 2001
Butane isomers solid waste incineration Leach et al., 1999
Butane isomers gasoline evaporation Lee et al., 2006
Isopentane fossil fuel evaporation from cars Hopkins et al., 2005
Isopentane traffic Tsai et al., 2006
Pentane isomers, butane traffic John, 1997
Pentane isomers, hexane nontailpipe, evaporative loss Lee et al., 2006
hexane and aromatics traffic Batterdam et al., 2002
Alkanes long range pollution from oil exploration Blake et al.