<p>Aerosols are solid or liquid particles that span in size from a few nanometers to tens of micrometers. They are important in both outdoor and indoor environments due to their impact on climate and human health. Many aerosol processes of interest to the environment, health, and filtration are strongly size-dependent. Aerosol particle size distributions (PSDs) provide a basis to better understand outdoor and indoor air pollution sources, evaluate human exposure to air pollution, and aerosol deposition in the human respiratory tract and filters in building ventilation systems. Monitoring the temporal evolution of aerosol PSDs enable for characterization of dynamic aerosol transport and transformation processes, such as direct emissions, nucleation, condensation, coagulation, resuspension, deposition, and filtration. This thesis presents three studies on the PSDs of: (i.) urban aerosols in cities around the world in order to identify geographical trends in the shape and magnitude of PSDs and to frame future research needs for PSD observations at a global-scale, (ii.) synthesized salt particles from a novel thermal aerosol generator to evaluate its suitability for air filter testing, and (iii.) indoor biological particulate matter (<i>bio</i>PM) to characterize transient inhalation exposures of infants and adults to resuspended <i>bio</i>PM from carpet dust induced by crawling and walking.</p> <p>First, this thesis presents the current state-of-knowledge of urban aerosol PSDs by critically analyzing <i>n</i>=793 urban aerosol PSD observations made between 1998 to 2017 in <i>n</i>=125 cities in <i>n</i>=51 countries across the following regions of the world: Africa (AF), Central, South, and Southeast Asia (CSSA), East Asia (EA), Europe (EU), Latin America (LA), North America, Australia, and New Zealand (NAAN), and West Asia (WA). Prominent geographical variations in the shape and magnitude of urban aerosol number and mass PSDs were identified and significant variations in number PSDs were found between cities in EU and NAAN with those in CSSA and EA. Most PSD observations published in the literature are short-term, with only 14% providing data for longer than six months. There is a paucity of PSDs measured in AF, CSSA, LA, and WA, demonstrating the need for long-term aerosol measurements across wide size ranges in many cities around the globe. Inter-region variations in PSDs have important implications for population exposure, driving large differences in the urban aerosol inhaled deposited dose rate received in each region of the human respiratory system. Similarly, inter-region variations in the shape of PSDs impact the penetration of urban aerosols through filters in building ventilation systems, which serve as an important interface between the outdoor and indoor atmospheres. The results of this critical review demonstrate that global initiatives are urgently needed to develop infrastructure for routine and long-term monitoring of urban aerosol PSDs spanning the nucleation to coarse modes.</p> <p>Second, this thesis evaluates a newly designed commercially available thermal aerosol generator for ageing air filters in building heating, ventilation, and air-conditioning (HVAC) systems. The physical characteristics of the synthesized salt aerosol (NaCl and KCl) under different generator operational conditions were evaluated. The shape of the number and mass PSD output of the thermal aerosol generator are similar to those found in outdoor (urban) and indoor air and can be modulated by varying the rate at which the salt stick is fed into the flame. The morphology of the NaCl and KCl particles varied with size, with compact spherical or cubic structures observed below 100 nm and agglomerates observed above 100 nm. The thermal aerosol generator is a cost-effective technique for rapid ageing of HVAC filters with a PSD that more accurately represents, compared to conventional loading dusts, what filters encounter in real HVAC installations.</p> <p>Lastly, this thesis characterizes infant and adult inhalation exposures and respiratory tract deposited dose rates of resuspended <i>bio</i>PM from carpets. Chamber experiments were conducted with a robotic crawling infant and an adult performing a walking sequence. Breathing zone (BZ) size distributions of resuspended fluorescent biological aerosol particles (FBAPs), a <i>bio</i>PM proxy, were monitored in real-time. FBAP exposures were highly transient during periods of locomotion. Both crawling and walking delivered a significant number of resuspended FBAPs to the BZ, with concentrations ranging from 0.5-2 cm^-3. Infants and adults are primarily exposed to a unimodal FBAP size distribution between 2 and 6 μm, with infants receiving greater exposures to super-10 μm FBAPs. In just one minute of crawling or walking, 10²-10³ resuspended FBAPs can deposit in the respiratory tract, with an infant receiving much of their respiratory tract deposited dose in their lower airways. Per kg body mass, an infant will receive nearly four times greater respiratory tract deposited dose of resuspended FBAPs compared to an adult.</p>

Electrospinning has been the focus of countless studies for the past decades for applications, including but not limited to, filtration, tissue engineering, and catalysis. Electrospinning is a one-step process for producing nano- and/or micro-fibrous materials with diameters ranging typically from 50 to 5000 nm. The simulation algorithm presented here is based on a novel mass-spring-damper (MSD) approach devised to incorporate the mechanical properties of the fibers in predicting the formation and morphology of the electrospun fibers as they travel from the needle toward the collector, and as they deposit on the substrate. This work is the first to develop a physics-based (in contrast to the previously-developed geometry-based) computational model to generate 3-D virtual geometries that realistically resemble the microstructure of an electrospun fibrous material with embedded particles, and to report on the filtration performance of the resulting composite media. In addition, this work presents a detailed analysis on the effects of electrospinning conditions on the microstructural properties (i.e. fiber diameter, thickness, and porosity) of polystyrene and polycaprolactone fibrous materials. For instance, it was observed that porosity of a PS electrospun material increases with increasing the needle-to-collector distance, or reducing the concentration of PS solution. The computational tool developed in this work allows one to study the effects of electrospinning parameters such as voltage, needle-to-collector distance (NCD), or polymer concentration, on thickness and porosity of the resulting fibrous materials. Using our MSD formulations, a new approach is also developed to model formation and growth of dust-cakes comprised of non-overlapping non-spherical particles, for the first time. This new simulation approach can be used to study the morphology of a dust-cake and how it impacts, for instance, the filtration efficiency of a dust-loaded filter, among many other applications.

In this study we examine the performance of 31 global model radiative transfer schemes in cloudfree conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scatteringonly aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multiangular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly −10 to 20 %, with over- and underestimates of radiative cooling at lower and higher solar zenith angle, respectively. Inter-model diversity (relative standard deviation) increases from ~ 10 to 15% as solar zenith angle decreases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

The ubiquitous abundance of organic compounds in natural and anthorpogenically influenced eco-systems has put these compounds into the focus of atmospheric research. Organic compounds have an impact on air quality, climate, and human health. Moreover, they affect particle growth, secondary organic aerosol (SOA) formation, and the global radiation budget by altering particle properties. To investigate the multiphase chemistry of organic compounds and interactions with the aqueous phase in the troposphere, modelling can provide a useful tool. The oxidation of larger organic molecules to the final product CO2 can involve a huge number of intermediate compounds and tens of thousands of reactions. Therefore, the creation of explicit mechanisms relies on automated mechanism construction. Estimation methods for the prediction of the kinetic data needed to describe the degradation of these intermediates are inevitable due to the infeasibility of an experimental determination of all necessary data. Current aqueous phase descriptions of organic chemistry lag behind the gas phase descriptions in atmospheric chemical mechanisms despite its importance for the multiphase chemistry of organic compounds. In this dissertation, the gas phase mechanism Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) has been advanced by a protocol for the description of the oxidation of organic compounds in the aqueous phase. Therefore, a database with kinetic data of 465 aqueous phase hydroxyl radical and 129 aqueous phase nitrate radical reactions with organic compounds has been compiled and evaluated. The database was used to evaluate currently available estimation methods for the prediction of aqueous phase kinetic data of reactions of organic compounds. Among the investigated methods were correlations of gas and aqueous kinetic data, kinetic data of homologous series of various compound classes, reactivity comparisons of inorganic radical oxidants, Evans-Polanyi-type correlations, and structure-activity relationships (SARs). Evans-Polanyi-type correlations have been improved for the purpose of automated mechanism self-generation of mechanisms with large organic molecules. A protocol has been designed based on SARs for hydroxyl radical reactions and the improved Evans-Polanyi-type correlations for nitrate radical reactions with organic compounds. The protocol was assessed in a series of critical sensitivity studies, where uncertainties of critical parameters were investigated. The advanced multiphase generator GECKO-A was used to generate mechanisms, which were applied in box model studies and validated against two sets of aerosol chamber experiments. Experiments differed by the initial compounds used (hexane and trimethylbenzene) and the experimental conditions (UV-C lights off/on and additional in-situ hydroxyl radical source no/yes). Reasonable to good agreement of the modelled and experimental results was achieved in these studies. Finally, GECKO-A was used to create two new CAPRAM version, where, for the first time, branchingratios for different reaction pathways were introduced and the chemistry of compounds with up to four carbon atoms has been extended. The most detailed mechanism comprises 4174 compounds and 7145 processes. Detailed investigations were performed under real tropospheric conditions in urban and remote continental environments. Model results showed significant improvements, especially in regard to the formation of organic aerosol mass. Detailed investigations of concentration-time profiles and chemical fluxes refined the current knowledge of the multiphase processing of organic compounds in the troposphere, but also pointed at current limitations of the generator protocol, the mechanisms created, and current understanding of aqueous phase processes of organic compounds.:1 Introduction and motivation 2 Theoretical background 2.1 General overview of the tropospheric multiphase chemistry of organic compounds 2.1.1 Gas phase chemistry 2.1.2 Phase transfer 2.1.3 Aqueous phase chemistry 2.2 Tropospheric multiphase chemistry mechanisms 2.2.1 Gas phase mechanisms 2.2.2 Aqueous phase mechanisms 2.2.3 The multiphase mechanism MCMv3.1-CAPRAM 3.0n 2.2.3.1 MCMv3.1 2.2.3.2 CAPRAM 3.0n 2.3 Multiphase chemistry box models 2.3.1 Overview 2.3.2 The model SPACCIM 2.3.2.1 Overview 2.3.2.2 The microphysical scheme 2.3.2.3 The chemical and phase transfer scheme 2.3.2.4 The coupling scheme 2.4 Prediction of aqueous phase kinetic data 2.4.1 Simple correlations 2.4.2 Evans-Polanyi-correlations 2.4.3 Structure-activity relationships 2.5 The generator GECKO-A 3 Evaluation of kinetic data and prediction methods 3.1 Compilation and evaluation of aqueous phase kinetic data 3.2 Extrapolation of gas phase rate constants to the aqueous phase 3.3 Homologous series of compound classes 3.4 Radical reactivity comparisons 3.5 Evans-Polanyi-type correlations 3.5.1 OH rate constant prediction 3.5.2 NO3 rate constant prediction 3.5.3 Development of an advanced Evans-Polanyi-type correlation 3.6 Structure-activity relationships 3.7 Conclusions from the evaluation process 4 Development of the new aqueous phase protocol and its implementation into GECKO-A 4.1 Initialisation and workflow of GECKO-A 4.2 Estimation of phase transfer data 4.3 OH reactions of stable compounds 4.4 NO3 reactions of stable compounds 4.5 Hydration of carbonyl compounds 4.6 Hydrolysis of carbonyl nitrates 4.7 Dissociation of carboxylic acids 4.8 Degradation of radical compounds 4.8.1 RO2 recombinations and cross-reactions 4.8.2 HO2 elimination of ff-hydroxy peroxy radicals 4.8.3 Degradation of acylperoxy radicals 4.8.4 Degradation of fi-carboxyl peroxy radicals 4.8.5 Degradation of alkoxy radicals 4.8.6 Degradation of acyloxy radicals 5 Investigation and refinement of crucial parameters in GECKO-A and CAPRAM mechanism development 5.1 Formation and degradation of polycarbonyl compounds in the protocol 5.2 Influence of the mass accommodation coefficient on the organic multiphase chemistry and composition 5.3 Influence of the cut-off parameter for minor reaction pathways 5.4 Influence of the chosen SAR in the protocol 5.5 Processing of organic mass fraction in the protocol 5.5.1 Parameterisations for radical attack of the overall organic mass fraction 5.5.2 Detailed studies of organic nitrate sinks and sources 5.5.3 Phase transfer of oxygenated organic compounds in the protocol 5.5.4 Decay of alkoxy radicals in the protocol 5.5.5 Revision of the GROMHE thermodynamic database 5.6 Influence of the nitrate radical chemistry 5.7 The final protocol for aqueous phase mechanism self-generation 5.8 CAPRAM mechanism development 5.8.1 CAPRAM 3.0 5.8.2 CAPRAM 3.5 5.8.3 CAPRAM 4.0 6 Model results and discussion 6.1 Comparisons of model results with aerosol chamber experiments 6.1.1 Design of the aerosol chamber experiments 6.1.1.1 Hexane oxidation experiment 6.1.1.2 Trimethylbenzene oxidation experiment 6.1.2 Mechanism generation and model setup 6.1.2.1 Hexane oxidation experiment 6.1.2.2 Trimethylbenzene oxidation experiment 6.1.3 Evaluation of the model versus aerosol chamber results 6.1.3.1 Hexane oxidation experiment 6.1.3.2 Trimethylbenzene oxidation experiment 6.2 Simulations with a ‘real atmosphere’ scenario 6.2.1 Model setup 6.2.2 Meteorological and microphysical parameters 6.2.3 Influence of the extended organic scheme on the particle acidity and SOA formation 6.2.3.1 Particle acidity 6.2.3.2 Particle mass 6.2.4 Influence of the extended organic scheme on inorganic radical oxidants 6.2.4.1 OH chemistry 6.2.4.2 NO3 chemistry 6.2.4.3 Comparison of OH and NO3 chemistry 6.2.4.4 HO2/O2- chemistry 6.2.5 Influence of the extended organic scheme on inorganic non-radical oxidants 6.2.5.1 H2O2 chemistry 6.2.5.2 O3 chemistry 6.2.6 Influence of the extended organic scheme on inorganic particulate matter 6.2.6.1 Sulfate chemistry 6.2.6.2 Nitrate chemistry 6.2.6.3 TMI chemistry 6.2.7 Detailed investigations of selected organic subsystems 6.2.7.1 Monofunctional organic compounds 6.2.7.2 Carbonyl compounds 6.2.7.3 Dicarboxylic acids and functionalised monocarboxylic acids 7 Conclusions References Glossary Acronyms List of symbols List of Figures List of Tables Acknowledgements Curriculum Vitae List of relevant publications Peer-reviewed publications Oral conference contributions Poster conference contributions Appendix A Overview of selected compound classes of tropospheric relevance B Detailed description of the function of SARs C The kinetic database C.1 Reactions of hydroxyl radicals with organic compounds C.2 Reactions of nitrate radicals with organic compounds D Detailed information about the evaluation of prediction methods D.1 Rate data used for the derivation and evaluation of gas-aqueous phase correlations D.2 Explanation of the use of box plots D.3 Additional correlations of homologous series of various compound classes D.4 Additional information of Evans-Polanyi-type correlations D.5 Additional information of structure-activity relationships E Additional information for the development of the protocol of GECKO-A E.1 Investigations on the decay of acylperoxy radicals E.2 Additional information about the sensitivity of mass accomodation coefficients E.3 Additional information about the sensitivity studies concerning the decay of polycarbonyls E.4 Additional information about the sensitivity studies concerning the omission of minor reaction pathways E.5 Additional information about the sensitivity studies concerning the processing of the organic mass fraction E.6 Additional information about the influence of the nitrate radical chemistry F Additional information about the mechanism generation and model initialisation F.1 List of primary compounds used for the generation of CAPRAM 3.5 F.2 List of primary compounds used for the generation of CAPRAM 4.0 F.3 Model initialization of the ‘real atmosphere’ scenarios G The CAPRAM oxidation scheme G.1 Photolysis processes G.2 Inorganic chemistry G.2.1 Phase transfer processes G.2.2 Chemical conversions G.3 Organic chemistry G.3.1 Phase transfer processes G.3.2 Chemical conversions H Detailed information about the model validation with chamber experiments H.1 Additional information about the initialisation of the hexane oxidation experiment H.2 Additional model results from the hexane oxidation experiment H.3 Additional information about the sensitivity runs used in the trimethylbenzene oxidation experiment H.4 Additional results from the TMB oxidation experiment I Additional results from the ‘real atmosphere’ scenario I.1 Particle acidity and SOA formation I.2 Radical oxidants I.3 Organic compounds References of the Appendix / Das zahlreiche Vorkommen organischer Verbindungen in natürlichen und anthropogen beeinflussten Ökosystemen hat diese Verbindungen in den Fokus der Atmosphärenforschung gerückt. Organische Verbindungen beeinträchtigen die Luftqualität, die menschliche Gesundheit und das Klima. Weiterhin werden Partikelwachstum und -eigenschaften, sekundäre organische Partikelbildung und dadurch der globale Strahlungshaushalt durch sie beeinflusst. Um die troposphärische Multiphasenchemie organischer Verbindungen und Wechselwirkungen mit der Flüssigphase zu untersuchen, sind Modellstudien hilfreich. Die Oxidation großer organischer Moleküle führt zu einer Vielzahl an Zwischenprodukten. Der Abbau erfolgt in unzähligen Reaktionen bis hin zum Endprodukt CO2. Bei der Entwicklung expliziter Mechanismen muss deshalb für diese Verbindungen auf computergestützte, automatisierte Methoden zurückgegriffen werden. Abschätzungsmethoden für die Vorhersage kinetischer Daten zur Beschreibung des Abbaus der Zwischenprodukte sind unabdingbar, da eine experimentelle Bestimmung aller benötigten Daten nicht realisierbar ist. Die derzeitige Beschreibung der Flüssigphasenchemie unterliegt deutlich den Beschreibungen der Gasphase in atmosphärischen Chemiemechanismen trotz deren Relevanz für die Multiphasenchemie. In dieser Arbeit wurde der Gasphasenmechanismusgenerator GECKO-A (“Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere”) um ein Protokoll zur Oxidation organischer Verbindungen in der Flüssigphase erweitert. Dazu wurde eine Datenbank mit kinetischen Daten von 465 Hydroxylradikal- und 129 Nitratradikalreaktionen mit organischen Verbindungen angelegt und evaluiert. Mit Hilfe der Datenbank wurden derzeitige Abschätzungsmethoden für die Vorhersage kinetischer Daten von Flüssigphasenreaktionen organischer Verbindungen evaluiert. Die untersuchten Methoden beinhalteten Korrelationen kinetischer Daten aus Gas- und Flüssigphase, homologer Reihen verschiedener Stoffklassen, Reaktivitätsvergleiche, Evans-Polanyi-Korrelationen und Struktur-Reaktivitätsbeziehungen. Für die Mechanismusgenerierung großer organischer Moleküle wurden die Evans-Polanyi-Korrelationen in dieser Arbeit weiterentwickelt. Es wurde ein Protokol für die Mechanismusgenerierung entwickelt, das auf Struktur-Reaktivitätsbeziehungen bei Reaktionen von organischen Verbindungen mit OH-Radikalen und auf den erweiterten Evans-Polanyi-Korrelationen bei NO3-Radikalreaktionen beruht. Das Protokoll wurde umfangreich in einer Reihe von Sensitivitätsstudien getestet, um Unsicherheiten kritischer Parameter abzuschätzen. Der erweiterte Multiphasengenerator GECKO-A wurde dazu verwendet, neue Mechanismen zu generieren, die in Boxmodellstudien gegen Aerosolkammerexperimente evaluiert wurden. Die Experimentreihen unterschieden sich sowohl in der betrachteten Ausgangssubstanz (Hexan und Trimethylbenzen) und dem Experimentaufbau (ohne oder mit UV-C-Photolyse und ohne oder mit zusätzlicher partikulärer Hydroxylradikalquelle). Bei den Experimenten konnte eine zufriedenstellende bis gute Übereinstimmung der experimentellen und Modellergebnisse erreicht werden. Weiterhin wurde GECKO-A verwendet, um zwei neue CAPRAM-Versionen mit bis zu 4174 Verbindungen und 7145 Prozessen zu generieren. Erstmals wurden Verzweigungsverhältnisse in CAPRAM eingeführt. Außerdem wurde die Chemie organischer Verbindungen mit bis zu vier Kohlenstoffatomen erweitert. Umfangreiche Untersuchungen unter realistischen troposphärischen Bedingungen in urbanen und ländlichen Gebieten haben deutliche Verbesserungen der erweiterten Mechanismen besonders in Bezug auf Massenzuwachs des organischen Aerosolanteils gezeigt. Das Verständnis der organischen Multiphasenchemie konnte durch detaillierte Untersuchungen zu den Konzentrations-Zeit-Profilen und chemischen Flüssen vertieft werden, aber auch gegenwärtige Limitierungen des Generators, der erzeugten Mechanismen und unseres Verständnisses für Flüssigphasenprozesse organischer Verbindungen aufgezeigt werden.:1 Introduction and motivation 2 Theoretical background 2.1 General overview of the tropospheric multiphase chemistry of organic compounds 2.1.1 Gas phase chemistry 2.1.2 Phase transfer 2.1.3 Aqueous phase chemistry 2.2 Tropospheric multiphase chemistry mechanisms 2.2.1 Gas phase mechanisms 2.2.2 Aqueous phase mechanisms 2.2.3 The multiphase mechanism MCMv3.1-CAPRAM 3.0n 2.2.3.1 MCMv3.1 2.2.3.2 CAPRAM 3.0n 2.3 Multiphase chemistry box models 2.3.1 Overview 2.3.2 The model SPACCIM 2.3.2.1 Overview 2.3.2.2 The microphysical scheme 2.3.2.3 The chemical and phase transfer scheme 2.3.2.4 The coupling scheme 2.4 Prediction of aqueous phase kinetic data 2.4.1 Simple correlations 2.4.2 Evans-Polanyi-correlations 2.4.3 Structure-activity relationships 2.5 The generator GECKO-A 3 Evaluation of kinetic data and prediction methods 3.1 Compilation and evaluation of aqueous phase kinetic data 3.2 Extrapolation of gas phase rate constants to the aqueous phase 3.3 Homologous series of compound classes 3.4 Radical reactivity comparisons 3.5 Evans-Polanyi-type correlations 3.5.1 OH rate constant prediction 3.5.2 NO3 rate constant prediction 3.5.3 Development of an advanced Evans-Polanyi-type correlation 3.6 Structure-activity relationships 3.7 Conclusions from the evaluation process 4 Development of the new aqueous phase protocol and its implementation into GECKO-A 4.1 Initialisation and workflow of GECKO-A 4.2 Estimation of phase transfer data 4.3 OH reactions of stable compounds 4.4 NO3 reactions of stable compounds 4.5 Hydration of carbonyl compounds 4.6 Hydrolysis of carbonyl nitrates 4.7 Dissociation of carboxylic acids 4.8 Degradation of radical compounds 4.8.1 RO2 recombinations and cross-reactions 4.8.2 HO2 elimination of ff-hydroxy peroxy radicals 4.8.3 Degradation of acylperoxy radicals 4.8.4 Degradation of fi-carboxyl peroxy radicals 4.8.5 Degradation of alkoxy radicals 4.8.6 Degradation of acyloxy radicals 5 Investigation and refinement of crucial parameters in GECKO-A and CAPRAM mechanism development 5.1 Formation and degradation of polycarbonyl compounds in the protocol 5.2 Influence of the mass accommodation coefficient on the organic multiphase chemistry and composition 5.3 Influence of the cut-off parameter for minor reaction pathways 5.4 Influence of the chosen SAR in the protocol 5.5 Processing of organic mass fraction in the protocol 5.5.1 Parameterisations for radical attack of the overall organic mass fraction 5.5.2 Detailed studies of organic nitrate sinks and sources 5.5.3 Phase transfer of oxygenated organic compounds in the protocol 5.5.4 Decay of alkoxy radicals in the protocol 5.5.5 Revision of the GROMHE thermodynamic database 5.6 Influence of the nitrate radical chemistry 5.7 The final protocol for aqueous phase mechanism self-generation 5.8 CAPRAM mechanism development 5.8.1 CAPRAM 3.0 5.8.2 CAPRAM 3.5 5.8.3 CAPRAM 4.0 6 Model results and discussion 6.1 Comparisons of model results with aerosol chamber experiments 6.1.1 Design of the aerosol chamber experiments 6.1.1.1 Hexane oxidation experiment 6.1.1.2 Trimethylbenzene oxidation experiment 6.1.2 Mechanism generation and model setup 6.1.2.1 Hexane oxidation experiment 6.1.2.2 Trimethylbenzene oxidation experiment 6.1.3 Evaluation of the model versus aerosol chamber results 6.1.3.1 Hexane oxidation experiment 6.1.3.2 Trimethylbenzene oxidation experiment 6.2 Simulations with a ‘real atmosphere’ scenario 6.2.1 Model setup 6.2.2 Meteorological and microphysical parameters 6.2.3 Influence of the extended organic scheme on the particle acidity and SOA formation 6.2.3.1 Particle acidity 6.2.3.2 Particle mass 6.2.4 Influence of the extended organic scheme on inorganic radical oxidants 6.2.4.1 OH chemistry 6.2.4.2 NO3 chemistry 6.2.4.3 Comparison of OH and NO3 chemistry 6.2.4.4 HO2/O2- chemistry 6.2.5 Influence of the extended organic scheme on inorganic non-radical oxidants 6.2.5.1 H2O2 chemistry 6.2.5.2 O3 chemistry 6.2.6 Influence of the extended organic scheme on inorganic particulate matter 6.2.6.1 Sulfate chemistry 6.2.6.2 Nitrate chemistry 6.2.6.3 TMI chemistry 6.2.7 Detailed investigations of selected organic subsystems 6.2.7.1 Monofunctional organic compounds 6.2.7.2 Carbonyl compounds 6.2.7.3 Dicarboxylic acids and functionalised monocarboxylic acids 7 Conclusions References Glossary Acronyms List of symbols List of Figures List of Tables Acknowledgements Curriculum Vitae List of relevant publications Peer-reviewed publications Oral conference contributions Poster conference contributions Appendix A Overview of selected compound classes of tropospheric relevance B Detailed description of the function of SARs C The kinetic database C.1 Reactions of hydroxyl radicals with organic compounds C.2 Reactions of nitrate radicals with organic compounds D Detailed information about the evaluation of prediction methods D.1 Rate data used for the derivation and evaluation of gas-aqueous phase correlations D.2 Explanation of the use of box plots D.3 Additional correlations of homologous series of various compound classes D.4 Additional information of Evans-Polanyi-type correlations D.5 Additional information of structure-activity relationships E Additional information for the development of the protocol of GECKO-A E.1 Investigations on the decay of acylperoxy radicals E.2 Additional information about the sensitivity of mass accomodation coefficients E.3 Additional information about the sensitivity studies concerning the decay of polycarbonyls E.4 Additional information about the sensitivity studies concerning the omission of minor reaction pathways E.5 Additional information about the sensitivity studies concerning the processing of the organic mass fraction E.6 Additional information about the influence of the nitrate radical chemistry F Additional information about the mechanism generation and model initialisation F.1 List of primary compounds used for the generation of CAPRAM 3.5 F.2 List of primary compounds used for the generation of CAPRAM 4.0 F.3 Model initialization of the ‘real atmosphere’ scenarios G The CAPRAM oxidation scheme G.1 Photolysis processes G.2 Inorganic chemistry G.2.1 Phase transfer processes G.2.2 Chemical conversions G.3 Organic chemistry G.3.1 Phase transfer processes G.3.2 Chemical conversions H Detailed information about the model validation with chamber experiments H.1 Additional information about the initialisation of the hexane oxidation experiment H.2 Additional model results from the hexane oxidation experiment H.3 Additional information about the sensitivity runs used in the trimethylbenzene oxidation experiment H.4 Additional results from the TMB oxidation experiment I Additional results from the ‘real atmosphere’ scenario I.1 Particle acidity and SOA formation I.2 Radical oxidants I.3 Organic compounds References of the Appendix

Über einen Zeitraum von zwei Jahren wurden vier sächsische Standorte beprobt und auf Bioaerosole analysiert. An jedem Standort wurden mindestens 12 Messtage im Zeitraum Mai bis Oktober realisiert. Untersucht wurden die Summenparameter Gesamtbakterienzahl, Gesamtpilzzahl und Endotoxine sowie die für Tierhaltungsanlagen festgelegten Leitparameter Staphylokokken spp., Enterokokken spp. und Staphylococcus aureus. Für Sachsen liegen damit erstmals hinreichend belastbare Daten über die Hintergrundkonzentration von für landwirtschaftliche Anlagen relevanten Bioaerosolen (VDI 4250 Bl. 3) vor. Mit diesen kann die Verfahrensweise im LAI-Bioaerosol-Leitfaden bezüglich der Einführung von Leitparametern bestätigt werden. Damit ist es möglich, im Rahmen von Genehmigungsverfahren die Hintergrundbelastung zu benennen.

Due to its prevalence over large, densely populated areas, ammonium nitrate is an important chemical species in aerosol research. However, due to its volatility at ambient temperatures and over low temperature gradients, ammonium nitrate can be a difficult species to accurately measure. The volatility of ammonium nitrate is known to be dependent on temperature, relative humidity, the internal mixing state of the particle, and availability of the precursor gas constituents. The particle's physical state affects the equilibrium constant value of the ammonium nitrate - nitric acid / ammonia exchange and helps determine the dissociation rate. For indoor aerosol research, the outdoor originating aerosol particles' exposure to the new physical conditions indoors, such as changes in temperature, humidity, and particle-surface reactions within the microenvironment all accelerate ammonium nitrate dissociation. This increased rate of partitioning can generate artifacts on datasets, increase indoor particle formation, and accelerate the corrosion of cultural antiquities through acidification. The magnitude of these impacts is uncertain due to the current lack of knowledge on particle transformation processes when outdoor originating particles migrate indoors. To address this gap in knowledge, this thesis...

In der vorliegenden Arbeit wurde das hygroskopische Wachstum sowie das Aktivierungsverhalten von biogenen sekundären organischen Aerosolpartikeln (SOA) betrachtet. Ziel der Arbeit war es, für verschiedene Arten von SOA eine rechnerische Schließung der hygroskopischen Wachstumsfaktoren, für den Bereich von relativen Feuchten > 90 %, sowie dem Aktivierungspunkt zu Wolkentropfen, mittels der Köhlergleichung zu erreichen. Betrachtet wurden SOA-Partikel, welche über dunkle Ozonolyse (ohne Vorhandensein von Licht) sowie Photolyse von alpha-Pinen in Laborversuchen, unter Variation der Reaktionsbedingungen, gebildet wurden. Mit zwei Messgeräten – dem High Humidity Tandem Differential Mobility Analyzer (HHTDMA) und dem Leipzig Aerosol Cloud Interaction Simulator (LACIS) – wurde das hygroskopische Wachstum bei relativen Feuchten von 80 % bis 99,4 % untersucht. Die kritische Übersättigung im Aktivierungspunkt der Partikel zu Wolkentropfen wurde mit einem Cloud Condensation Nuclei Counter (CCNC) bestimmt. Weiterhin kam zur chemischen Charakterisierung der verschiedenen SOA-Arten ein Aerosol-Massenspektrometer (AMS) zum Einsatz. Die experimentellen Arbeiten hierzu wurden am Leibniz-Institut für Troposphärenforschung durchgeführt. Anhand von Schließungsrechnungen konnte für alle in der vorliegenden Arbeit untersuchten SOA-Arten gezeigt werden, dass der Hygroskopizitätsparameter kappa aus der kappa-Köhlertheorie mit zunehmender relativer Feuchte variiert. So nahm mit zunehmender relativer Feuchte zunächst ab und stieg, nach Erreichen eines Minimums bei Werten von etwa 96 – 98 % relativer Feuchte, anschließend steil an. Dabei zeigte sich dieser Kurvenverlauf abhängig von den Reaktionsbedingungen bei der Bildung der SOA-Partikel. Der Hygroskopizitätsparameter konnte dabei mit einer im Rahmen dieser Arbeit entwickelten Funktion für alle hier untersuchten SOA-Arten beschrieben werden. In einem letzten Schritt wurde diese Funktion zur Beschreibung von mittels der O/C-Verhältnisse, welche aus den AMS-Messungen ermittelt wurden, parametrisiert. Somit konnten die gemessenen Werte der verschiedenen SOA-Arten besonders für relative Feuchten nahe dem Aktivierungspunkt erfolgreich beschrieben werden.

For the first time, a comprehensive characterization of optical, microphysical, and cloud-relevant properties of Central Asian aerosol particles with a state-of-the-art lidar has been performed. This study fills a gap between observations in Eastern Mediterranean (e.g., in Greece, Cyprus, and Israel) and Eastern Asian (e.g, in China, Korea, and Japan) aerosol monitoring. During the Central Asian Dust Experiment (CADEX), an automatic multiwavelength polarization Raman lidar PollyXT was operated in Dushanbe, Tajikistan, from 17 March 2015 until 31 August 2016. During the 18-month campaign, on 487 days, lidar data has been acquired for a time period of at least 3 h. On 308 of these days, the lidar ran even longer than 20 h. 328 manually analyzed profiles of nighttime observations build the data basis of this study and cover well the annual cycle of dust and pollution aerosol layering. Thorough quality assurance and calibration efforts have been made before, during, and after the measurement campaign. With the lidar, vertical profiles of the particle backscatter coefficient at 355 nm, 532 nm, and 1064 nm, of the particle extinction coefficient at 355 nm and 532 nm, and of the particle linear depolarization ratio at 355 nm and 532 nm wavelength were determined. From these quantities, lidar ratios and backscatter-related and extinction-related Ångström exponents were derived. Furthermore, the optical properties were converted to mass concentration and cloud-relevant parameters (CCN and INP concentration) by means of the recently developed lidar technique POLIPHON.

In der oberen Troposphäre und untersten Stratosphäre (OT/US) beeinflussen Aerosolpartikel im Submikrometerbereich den Strahlungshaushalt der Erde direkt und, was noch wichtiger ist, indirekt, da sie als Kondensationskern für Wolken dienen und somit die Spurengaskonzentrationen durch heterogene chemische Prozesse ändern können. Seit 1997 gibt es regelmäßige in situ Messungen der OT/US Partikel durch das Leibniz-Institut für Troposphärenforschung in Leipzig, Deutschland. Diese Messungen werden an Bord eines Passagierflugzeugs mit dem weltweit einzigartigen IAGOS-CARIBIC Messcontainer durchgeführt (www.iagos.org/iagos-caribic). In der vorliegenden Arbeit wurden die Partikelanzahlkonzentration und die Partikelgrößenverteilung im Submikrometerbereich der vergangenen Jahre ausgewertet. Dafür wurden die Daten von drei Kondensationspartikelzählern (CPC, Condensation Particle Counter) und einem optischen Partikelgrößenspektrometer (OPSS, Optical Particle Size Spectrometer) verwendet. Zunächst wurde im Labor eine umfangreiche Charakterisierung des IAGOS-CARIBIC OPSS hinsichtlich der Zähleffizienz durchgeführt. Weiterhin wurde eine Kalibrierung mit Polystyrol-Latex im geräterelevanten Bereich von 140 nm bis 1050 nm vorgenommen und daraus mit Hilfe der Mie-Streuung eine Funktion zur Datenauswertung für die OT/US entwickelt. Die statistische Analyse der IAGOS-CARIBIC OPSS und CPC Daten gibt einen guten Überblick über die in der OT/US vorkommenden Partikelanzahlkonzentrationen und stellt sicher, dass ein statistisch fundierter Datensatz für die Analyse zur Verfügung steht. Auf dieser Grundlage wurde zum ersten Mal eine detaillierte Analyse der raumzeitlichen Verteilung der Aitkenmode- und Akkumulationsmode-Partikelanzahlgrößenverteilung in der OT/US vorgenommen. Diese Analyse beinhaltet Weltkarten mit Medianwerten, Wahrscheinlichkeitsdichtefunktionen für spezielle Flugrouten und Partikelgrößenverteilungen entlang der Längengrade. Außerdem wurden die Partikelanzahlkonzentrationen zum ersten Mal mit dem globalen Klimamodell ECHAM-HAM verglichen. Dabei ergab sich, dass die Partikelanzahlkonzentration hauptsächlich von großräumigen Strömungsverhältnissen beeinflusst wird, was im Großen und Ganzen gut vom Modell wiedergegeben wird. Für die einzelnen Jahreszeiten wurden mit Hilfe der potentiellen Temperatur und äquivalenten Breitengrade die vertikalen Profile ausgewertet. Für die Analyse in Bezug auf die Aerosol-Mikrophysik und den Transport durch die Tropopause wurden auch die in IAGOS-CARIBIC gemessenen Spurengase, wie z.B. Ozon und Wasserdampf, hinzugezogen. Die Auswertung zeigt ebenfalls deutlich den Einfluss von Wolken in der oberen Troposphäre und verschiedene Austauschprozesse zwischen der Stratosphäre und Troposphäre. Außerdem wurde der Einfluss verschiedener Austauschprozesse auf die Partikelanzahlkonzentration untersucht: die Brewer-Dobson Zirkulation, warm conveyor belts, Isentropentransport und der Transport durch tropische, hochreichende konvektive Bewölkung. In der Vergangenheit wurde diese Analyse nur für atmosphärische Spurengase durchgeführt, und nun zum ersten Mal auch für Aerosolpartikel. Die hier präsentierten Ergebnisse zeigen eine umfangreiche Charakterisierung der Aitken- und Akkumulationsmode-Partikelanzahlkonzentration in der OT/US und den Einfluss von Austauschprozessen der Stratosphäre und Troposphäre auf die Partikel. Die Auswertungen tragen maßgeblich zum Verständnis und zur Vorhersage der Partikelanzahlkonzentration in Klimamodellen und damit schlussendlich zur Berechnung des Strahlungshaushalts der Erde und dessen zeitlicher Veränderung bei. / Submicrometer aerosol particles in the upper troposphere and lowermost stratosphere (UT/LMS) influence the Earth's radiation budget directly and, more important, indirectly, by acting as cloud condensation nuclei and by changing trace gas concentrations through heterogeneous chemical processes. Since 1997, regular in situ measurements of UT/LMS particles have been conducted by the Leibniz Institute for Tropospheric Research, Leipzig, Germany, using the world-wide unique IAGOS-CARIBIC observatory (www.iagos.org/iagos-caribic) onboard a passenger aircraft. In this thesis, UT/LMS aerosol particle number concentrations and the submicrometer aerosol particle size distribution as measured by three condensation particle counters (CPCs) and one Optical Particle Size Spectrometer (OPSS) are discussed. Before analyzing the measurement data from the UT/LMS region a throughout characterization of the IAGOS-CARIBIC OPSS with respect to the counting efficiency was carried out in the laboratory for the OPSS-relevant particle size range of 140 nm to 1040 nm diameter. After calibration with polystyrene latex (PSL) particles a theoretical response function, representative for the UT/LMS, was calculated with Mie theory to ensure a correct data analysis. The statistical analysis of the IAGOS-CARIBIC OPSS and CPC data gives a good overview of existing particle number concentrations in the UT/LMS and ensures a statistically sound data analysis. On this basis a detailed characterization of the spatio-temporal distribution of Aitken and accumulation mode particle number concentrations in the UT/LMS was carried out for the first time. This analysis includes global maps with median values, probability density functions for specific flight routes, and longitudinal distributions of the particle size distribution. Also a first comparison with the global climate model ECHAM-HAM was conducted. The analysis showed that the aerosol distributions are mainly influenced by large-scale circulation patterns which were, in gererel terms, well reflected by the global climate model. Moreover, seasonal vertical cross-sections for particle number concentrations, the potential temperature, and the equivalent latitude were generated. The results are interpreted with respect to aerosol microphysics and cross-tropopause transport using IAGOS-CARIBIC trace gases like ozone and water vapor. The influence of clouds in the troposphere and the different stratosphere-troposphere exchange processes are clearly visible. Furthermore, the influence of the major transport processes into the UT/LMS region on the aerosol particle number concentrations was investigated: the Brewer-Dobson circulation, warm conveyor belts, isentropic transport, and tropical deep convective cloud outflow. In the past this was done only for atmospheric trace gases, but now for the first time for aerosol particles. The findings presented in this study represent a comprehensive characterization of the Aitken and accumulation mode particle number concentration in the UT/LMS and the influence of stratospheric-tropospheric exchange processes on these particles. These findings may help to evaluate and improve predictions of particle number concentrations by climate models and finally the calculation of the Earth's radiation budget and its change over the years.

Certain models of NIOSH-approved filtering facepiece air purifying respirators are manufactured with stapled head straps. Depending on the manufacturer, these head straps may be stapled to the filter media itself. This may cause leakage through the filter media of the respirator, potentially exposing the user to an unacceptable level of contaminant. In this study, monodisperse polystyrene latex (PSL) spheres were generated to challenge four replicates of a N95 single use respirator model made by the same manufacturer. Nominal particle sizes of the PSL spheres used to challenge the respirators were 0.5, 1, and 2 micrometers in diameter. All respirators were sealed onto a custom built testing assembly and tested in a sealed chamber. Particle sizes of interest were generated using a nebulizer, and passed through a diffusion dryer and a Krypton-85 radioactive source prior to entering the test chamber. The dryer reduces the humidity of the aerosol generating by the nebulizer, while the radioactive source neutralizes the charge of the aerosol cloud. The test chamber was constructed using a glass aquarium measuring 32 x 53 x 122 centimeters. Three stainless steel air diffusers were placed above the testing compartment to evenly distribute the aerosol in the chamber. An exhaust manifold was placed at the lower part of the chamber beneath another stainless steel diffuser below the area where test respirators were placed. The respirators were challenged as received from the manufacturer with 0.5, 1 and 2 micrometer-sized (PSL) spheres. The same procedure was repeated for each respirator after sealing the areas where the head straps were stapled with silicon rubber. Testing was conducted at a flow rate of 85 liters per minute, as specified in the NIOSH respirator testing protocol. A laser particle counter was used to measure the concentration inside and outside of the respirator. The results showed unsealed efficiencies for particle sizes 0.5, 1, and 2 micrometers of 96.68%, 99.72%, 99.88% and sealed efficiencies of 97.35%, 99.82%, 99.93% respectively. There were no differences for particle size or sealing at 1.0 and 2.0 micrometers. A significant drop in efficiency was observed when testing with 0.5 micrometer PSL spheres. The drops in efficiency are not sufficient to reduce the integrity of the respirator for N95 certification. However, the leakages detected will have a cumulative effect when added to other sources of single use respirator leakage in the field.