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Experimenteel onderzoek naar de depositie van kolenstof op glas (kasdekken) en de daardoor veroorzaakte lichttransmissievermindering. Daarnaast een model- en literatuurstudie naar de gevolgen van verminderde lichttransmissie bij kasgewassen voor de opbrengst en naar de mogelijke gevolgen van kolenstofdepositie voor vollegrondsteelten. Voor kasteelten wordt geconcludeerd dat een vermindering van de fotosynthese-snelheid in de praktijk in hoofdzaak veroorzaakt wordt door lichtonderschepping, en dat onder omstandigheden waarbij het licht beperkend is 1% lichtonderschepping gepaard gaat met ongeveer 1% groeireductie. Deze omstandigheden doen zich in Nederland vrijwel altijd voor. Voor vollegrondsteelten lijkt geen negatief effect te verwachten

Different processes can influence the perticle size distribution of fresh automobile aerosols. Dispersion, deposition and polydispers coagulation according to Fuchs (1964) are discussed. The monodispers coagulation theory of Davies (1979) and the formula describing the gradient coagulation are extended to polydispers aerosols. Also a critical review is given of the behavious of submicron particles under the influence of the relative humidity and the reentrainment of these particles by tubulence.A survey is given of the electrical aerosolanalyzer and condensation nucleus counter. The control and comparison of these instruments is treated next. After that a literature review of the particle size distributions of traffic aerosols and the emissions which can be calculated from these distributions is presented.The emission in particles/km per vehicle can be derived from the size distribution measurements of aerosols and tracergas concentrations along a road, because the dispersion is known for the tracergas. As the aerosol samples were taken at different distances from the road, with different residence times, the velocity of coagulation and deposition can be deduced. Also one model is used to describe the three processes dispersion, deposition and coagulation. With the measurements along a road an experimental verification of this model was possible.The measured particle size distributions in a tunnel were a steady state concentration. The loss of aerosol bij dispersion, deposition and coagulation is compensated by the traffic emission. With this steady state concentration and the emission by traffic found during the roadexperiments the coagulation constant of submicron particles can be calculated. As a conclusion from these calculations a preference can be given to the theory of DAVIES (1979) above the theory of FUCHS (1964) describing the value of the coagulation constant. With a model that describes the steady state concentration in the tunnel as a function of the emission and removal mechanisms the traffic emission in the tunnel could be calculated.The emissions from the road and tunnel experiments have been evaluated and are in a reasonable agreement. The following emission in particles per vehicle is presented with a variation coefficient between 20% for the bigger particles and 70% for particles of 0.01 μm

IntroductionAir pollution components are present as gases and as particulate matter. As particle deposition takes place in various parts of the respiratory system particulate matter may have other toxicological implications than gaseous pollutants, which all may penetrate in the lower part of the respiratory tract. In addition, suspended particulate matter represents a group of pollutants of variable physical as well as chemical composition. Therefore airborne particulate matter cannot be regarded as a single, pure pollutant.This study deals with the mutagenic potency of airborne particulate matter bound organics and some of its toxicological implications.The assessment of health hazards is not easily possible without knowledge of the chemical character of the particles. Risk assessment through a toxicological consideration of the individual constituents has serious drawbacks because of the large number of chemicals involved and the complexity of the mixture. Since only 30-40% of the organic compounds on airborne particles have been identified, the contribution of unidentified compounds to the toxicological risk may be significant. Therefore the assessment of the overall mutagenic or carcinogenic activity in air samples may provide a more realistic basis for the evaluation of the possible risks, than an evaluation on the basis of individual compounds.The Salmonella /microsome assay has been a major assay used for monitoring the mutagenic potential of complex environmental mixtures such as airborne particulate matter. Results obtained with this test system may also be useful as a general air pollution parameter, representing particle bound extractable organics.The Salmonella /microsome assay involves subsequently sample collection, extraction, exposure of the test strain and the quantitative assessment of the revertants. Extraction is carried out routinely with organic solvents, while generally liver homogenates are used to identify mutagens which require metabolic activation. In the first part of this study methanol and liver homogenates from Aroclor 1254-pretreated Wistar rats were used to study the occurrence of particle bound mutagens collected indoors and outdoors. In the second part of this study physiological fluids and lung homogenates, which are more representative for the environment particles encounter in lungs, are used as solvent and metabolizing system in the Salmonella /microsome assay. Also cytotoxicity of airborne particulate matter to rat alveolar macrophages was determined in order to study some toxicological implications of inhalation of particle bound organic compounds.Mutagenic activity of extracts of airborne particulate matter from outdoor and indoor environmentsChapter 1 provides a summary of literature data on physical and chemical characteristics of airborne particulate matter.The occurrence of mutagens in the environment and their sources are discussed.Chapter 2 presents data on in vitro testing of airborne particles, collected outdoors. Much evidence exists on the mutagenicity of airborne particles at urban and industrial locations. This study shows that particulate matter at background (Terschelling) and rural locations (Wageningen) may also bear mutagenic compounds. In Wageningen the level of mutagenicity follows a yearly cycle, the highest activity being found in winter. Over the years considerable differences in mutagenicity were found. The correlation of mutagenicity of samples simultaneously collected on the same day at both locations and the relation between mutagenicity of air samples and wind direction and with air trajectories suggest that the mutagenic potential of suspended matter originates not from local sources but rather depends on large scale processes. This is supported by literature data which show that the mutagenic potential mainly occurs on the smallest particles which, as a result of their long residence time, may be transported over distances of thousands of kilometers.The air, sampled at rural and background locations contains direct as well as indirect acting mutagens. The addition of liver microsomes gives variable effects on the level of mutagenic activity. Increases or decreases, if found are mostly relatively small. Furthermore, mutagenic activity was correlated with commomly measured air pollution parameters; multiple regression showed that SO 2 , NO 2 , NO, CO and 0 3 together account for 70% of the variation' in direct mutagenicity and 80% of the variation of indirect activity. SO 2 and NO 2 , and SO 2 , NO 2 and CO were significantly associated with the variation in direct and indirect activity respectively.As variations in mutagenic activity can be explained to a large extent by commonly registered air pollutants, monitoring the mutagenic burden of aerosols does not contribute to our knowledge already obtained by monitoring SO 2 , NO x and CO.Chapter x 3 and chapter 4 deal with the comparison of particle bound mutagens collected indoors and outdoors. In chapter 3 the contribution of smoking and cooking and in chapter 4 the contribution of wood combustion to mutagenicity of indoor aerosols is established. The results show that not only extracts of outdoor particles, but also indoor particulate matter may contain mutagenic compounds. Comparison of the mutagenic activity indoors and outdoors indicates that outdoor extracts show a direct mutagenic activity which is clearly detectable in nearly all samples, whereas indoor samples mostly show a low or undetectable direct activity. It is found that the indirect mutagenic activity is generally larger in indoor samples than in outdoor samples. Morever in indoor extracts cytotoxic effects are more pronounced.One of the sources of indoor mutagens may be penetration of outdoor particles. In the winter 82/83 no contribution of outdoor sources to mutagenic activity indoors was observed, while in the winter 84/85 a correlation between the extremely high levels of outdoor mutagenicity and indoor mutagenic activity was found. However, the important differences in composition of simultaneously collected indoor and outdoor samples which manifest themselves by the ratio - S9/+S9 justifies the conclusion that penetration of outdoor particles may be one but certainly not the only source of mutagenic activity indoors. Mostly the contribution of outdoor sources to indoor mutagenicity is only small.From our studies it is obvious that cigarette smoking is the predominant source of airborne genotoxicity in homes. wood combustion appeared to be a second important factor producing genotoxic compounds as sometimes a 2-3 fold increase of mutagenic activity is found. Volatilization of cooking products represents a less important source of mutagens.From these experiments it may be concluded that the removal of mutagens to the outdoor environment is not complete.Exposure is a function of concentration and time. In The Netherlands people spend most of the time at home. As all indoor samples show a strong indirect mutagenic activity, it may be concluded that exposure to genotoxins will be determined to a large extent by the level of pollution inside homes, which implies that exposure to indirect acting mutagens is quantitatively of far greater concern than exposure to direct acting mutagens.Biological availability of particle bound organic compoundsChapter 5 reviews a number of studies which deal with some aspects of the biological fate of mutagenic compounds and their 'carrier' particles. Respirable airborne particles to which most potential mutagenic compounds, detected in the Ames assay, are adsorbed may deposit in various parts of the respiratory tract. one of the defence mechanisms with regard to possible harmful action of these particles is clearance, as it reduces residence time on potentially sensitive epithelial surfaces. Alveolar macrophages provide the initial defence of the lower respiratory tract towards particulate matter.In chapter 6 results show a significant reduction of phagocytic activity in rat alveolar macrophages in vitro after exposure to extracts of airborne particulate matter, and the effect was greatest with indoor air. Metabolizing enzymes, together with transformed or not transformed particles may be released in the alveolar spaces as a result of damage to alveolar macrophages.In chapter 7 dissolution of particle bound organics into newborn calf serum and lung lavage fluid from pigs is described. Although from our results it is clear that physiological fluids, especially when obtained from lung lavage are less efficient in removing mutagens than organic solvents, the suggestion seems to be justified that a certain elution of environmental chemicals into body fluids takes place.Chapter 8 deals with metabolic activation of extracts of indoor and outdoor particulate matter. Drug metabolizing enzyme systems may also be seen as a defence mechanism towards chemicals invading the body. These enzyme systems enable the organism not only to convert lipid soluble harmful drugs into harmless water soluble metabolites, but also more toxic or mutagenic metabolites may be formed. Our results show that in addition to liver, lung homogenates of rat (Wistar) and mouse (Swiss) are also able to activate extracts of airborne particulate matter in a comparable way. Uninduced liver and lung homogenates showed only minor differences in activation capacity in the metabolism of airborne particles. In contrast to liver homogenates, Aroclor 1254- pretreatment of test animals did not give a strong induction in metabolic activation capacity of lung homogenates.In liver, almost all cells contribute to metabolic capacity, whereas in the lung metabolic capacity is almost exclusively located in the Clara cells, which is only one of the 40 different lung cell types. In certain parts of the lungs, especially in the terminal bronchioles, in which Clara cells are located, a rather high metabolic activation may take place. Therefore these results suggest that the respiratory system may be an important site for in vivo bioactivation of respirable particles.

1.4.1 Scope of this thesisA few models for ammonia and ammonium exist. Russell et al. (1983) made a multi-layer Lagrangian transport model describing the transport and formation of ammonium nitrate aerosol for California. They did not take reactions of ammonia and sulphuric acid into account, nor wet deposition. Their model was mainly used to compute diurnal variations of ammonium nitrate aerosol, ammonia and nitric acid concentrations, which were compared with measurements for one day.De Leeuw et al. (1986) developed a multi-layer Lagrangian transport model with detailed chemistry including the reaction with sulphuric acid containing aerosol and wet deposition. Their model was especially designed to describe episodes with high aerosol concentrations.More complicated models as discussed above have the advantage of giving more insight in detailed (chemical) mechanisms. But the results obtained with such models are often difficult to verify as components are involved which are not measured, or not at all levels the model gives results for. Moreover, more complicated models require relatively more computing time, which makes them less suitable to compute long-term average concentrations. At this moment no good information is available on seasonal variations in the ammonia emission. Moreover, much Information on the variation both in time and space of other processes is also lacking. This means that some processes involved can be described in detail, whereas others cannot. Such models suffer then from an imbalance in the treatment of different processes, and the results of the models will be no better than is dictated by the weakest link in the chain. It should be mentioned here that such models still can be very valuable to study mechanisms and possible interactions between different processes and components. But because of the lacking information on e.g. short-time variation in emission no realistic short-term concentrations can be obtained.Some information on the processes involved is available, but sometimes only on a yearly basis. It seems therefore most appropriate to integrate the existing knowledge by using a relatively simple model for the computation of yearly averaged concentrations. A first attempt to do this was made by Fisher (1984). He tried to compute deposition fields for ammonium in precipitation and the total deposition (sum of dry and wet deposition) of NHx (sum of ammonia and ammonium) for Europe. But he had to conclude that his approach would remain limited until the main rates of removal of nitrogen compounds were better known.The scope of this thesis is:a. To evaluate the existing knowledge of all processes involved.b. To acquire additional crucial information on some processes from own field measurements.c. To integrate this knowledge by applying a model for the computation of long-term average (ground level) concentrations, with emphasis on the European scale. This model has been developed especially for ammonia and ammonium.d. To show some new applications of models: computation of historical import/export balances and concentration patterns.1.4.2. On the presentationThis thesis consists mainly of separate articles (chapters 3 to 6) which were submitted to Atmospheric Environment. This has some consequences:a. Some information is presented in more than one article or part of this thesis.b. A list of references appears after each chapter.c. The articles have not been written at the same time. As a result some information was not yet known at the time of preparation of some articles, although this does not lead to any serious inconsequences.In the following a preview is given of the contents of the different chapters.Chapter 2In this chapter some information is presented on the geographical distribution of the yearly averaged ammonia emission in Europe, which is essential to understand the model results.Chapter 3In this chapter field measurements are described. These measurements were performed for the following purposes:a. To verify the estimated emission densityb. To get an indication on the vertical concentration profiles of ammonia, ammonium and related components In an area where emission occurs. This information is needed to model the horizontal transport.c. To get an indication of the overall conversion rate of ammonia to ammonium.Chapter 4In this chapter is described how correction factors can be computed which can be used in a simple Lagrangian long-range transport model to describe the effects of turbulent mixing on concentration and deposition patterns. By using these correction factors more realistic results can be obtained.Chapter 5This chapter forms the basic part of the thesis and describes the evaluation and integration of the present knowledge, the setup of the model, numerical aspects of the model and comparison of model results with measurements. Although the model in principle would allow to vary most parameters as a function of time and space (e.g. dry deposition velocity, reaction rate, mixing height etc.) this was not done in practice in view of all uncertainties in the parameter values. Therefore, also no processes like escape into the reservoir layer were taken into account.Chapter 6In this chapter it is shown that it is not only possible to use a model to describe the present situation, but also to give estimates of concentrations in the past. These estimates make it possible to know where trends in concentrations measured in the past can be expected.Chapter 7In this chapter the conclusions of this study are summarized and discussed. Via inventarisatie van de beschikbare kennis der betrokken processen en stoffen, aangevuld met eigen metingen en modeltoepassingen is getracht de atmosferische kringloop van ammoniak en ammonium op Europese schaal voor de jaren 1870, 1920, 1950 en 1980 in kaart te brengen. Via het modelonderzoek wordt ook voor elk land in Europa afzonderlijk aangegeven uit welke landen de daar terechtgekomen hoeveelheid ammoniak en ammonium afkomstig is. Circa 72% van de depositie van ammoniak en ammonium in Nederland blijkt veroorzaakt te worden door emissie in Nederland zelf

This thesis treats aerosol behaviour under various conditions in enclosed spaces. Knowledge of this behaviour is of importance for the use of aerosol-filled enclosures as a supply of aerosol, as a means for aerosol characterization and for so-called smog chambers for air pollution research (mainly for the investigation of photochemical processes by which usually particles are formed).Chapter 1 gives a brief literature survey, indicating the limited attention given hitherto to aerosol behaviour in enclosed spaces. After decades of almost exclusive interest from meteorologists, since the beginning of the sixties, enclosed aerosols have become an important research subject in nuclear safety. Nuclear aerosol research, however, pertains mainly to high aerosol mass concentrations.In chapter 2 a model is given, describing aerosol removal from enclosed spaces. Usually, aerosol deposition on the walls occurs from a cloud with homogeneous space distribution due to thermal convection. The rate-limiting step of deposition is the transport through the boundary layer at the walls. Relations are derived for a number of removal mechanisms: sedimentation, diffusion, thermophoresis, diffusiophoresis, electrophoresis and photophoresis. From literature data and Fuchs' theory a relation is derived for the dependence of the boundary layer thickness δfor diffusive deposition on the diffusion coefficient D of aerosol particles in usual containments. Boundary conditions for non-stirred deposition of aerosols by sedimentation and diffusion are given.Chapter 3 summarizes the most important means used for experiments.In chapter 4 the experimental results and conclusions are presented. It consists of four sections dealing with unheated dry enclosures, heated dry enclosures, enclosures with a heated pool of liquid, and smog chambers, respectively.Observations on the behaviour of monodisperse and polydisperse aerosols in unheated dry enclosures support the model derived for sedimentation and diffusion. Additionally, the relation between δand D derived in chapter 2 is validated. Particles larger than a few tenths of a micron are removed by sedimentation; particles smaller than about 0.1 μm aresubject to diffusive deposition, though often electrophoresis plays an important role (particularly, in case of particles of about 0.1 μm). It is shown that aerosol measurements in containments can be used for determination of dynamic shape factors and aerodynamic diameters.Aerosols in heated dry containments are removed by thermophoresis. Observations on a large variety of aerosols and enclosures are in fair agreement with the model on thermophoretic removal derived in chapter 2. Interpretation of the experimental results yields the thermophoretic properties of aerosols. The results support the theories of Brock and Stetter, and are in disagreement with those of Derjaguin and Epstein. In accordance with theoretical predictions, thermophoretic decay constants are obtained independent of particle size (≥0.5 μm), of particle material and of temperature. Gentle heating of the floor of a containment is shown to have a stabilizing effect on the enclosed aerosol.Introduction of aerosol in a containment with a heated pool of liquid on the floor leads to particle growth by vapour condensation followed by an accelerating removal by sedimentation. Experimental observations support a model describing aerosol behaviour in such systems. The knowledge of this aerosol behaviour allows study of condensation on aerosol particles and particle growth under conditions of variable degrees of supersaturation. The degree of supersaturation can be varied by means of the heating power dissipated in the pool of liquid as well as by means of solving substances in the liquid.Investigations of aerosol behaviour in photochemical smog chambers show insignificant deposition due to thermophoresis or photophoresis under these conditions. Observed aerosol stabilities could be explained by electrophoretic deposition, yielding a coherent picture with electrophoresis in other investigations. Coagulation constants of aerosol could be calculated from measurements on number concentrations of aerosols in enclosed spaces. The results obtained agree fairly well with Davies' theory on coagulation. Decay curves of number concentration of aerosols in metal vessels can be used for assessment of diffusion coefficients.

Gedurende de maanden augustus en september 1981 is een onderzoek gedaan naar de geuremissies bij een drietal geselecteerde leghennenstallen. De stallen verschilden in mestbehandelingswijze en ventilatiesysteem. Het uitgevoerde onderzoek was een herhaling van een onderzoek uit 1979. Geconcludeerd kan worden dat de resultaten in grote lijnen overeenkomen met het eerder uitgevoerde onderzoek

Verslag wordt gedaan van een bezoek aan Pfizer GMBH Karlsruhe met gesprek en demonstratie van meetapparatuur. Tevens wordt een waardeoordeel gegeven over deze wijze van stofbestrijding.

This thesis treats aerosol behaviour under various conditions in enclosed spaces. Knowledge of this behaviour is of importance for the use of aerosol-filled enclosures as a supply of aerosol, as a means for aerosol characterization and for so-called smog chambers for air pollution research (mainly for the investigation of photochemical processes by which usually particles are formed).Chapter 1 gives a brief literature survey, indicating the limited attention given hitherto to aerosol behaviour in enclosed spaces. After decades of almost exclusive interest from meteorologists, since the beginning of the sixties, enclosed aerosols have become an important research subject in nuclear safety. Nuclear aerosol research, however, pertains mainly to high aerosol mass concentrations.In chapter 2 a model is given, describing aerosol removal from enclosed spaces. Usually, aerosol deposition on the walls occurs from a cloud with homogeneous space distribution due to thermal convection. The rate-limiting step of deposition is the transport through the boundary layer at the walls. Relations are derived for a number of removal mechanisms: sedimentation, diffusion, thermophoresis, diffusiophoresis, electrophoresis and photophoresis. From literature data and Fuchs' theory a relation is derived for the dependence of the boundary layer thickness δfor diffusive deposition on the diffusion coefficient D of aerosol particles in usual containments. Boundary conditions for non-stirred deposition of aerosols by sedimentation and diffusion are given.Chapter 3 summarizes the most important means used for experiments.In chapter 4 the experimental results and conclusions are presented. It consists of four sections dealing with unheated dry enclosures, heated dry enclosures, enclosures with a heated pool of liquid, and smog chambers, respectively.Observations on the behaviour of monodisperse and polydisperse aerosols in unheated dry enclosures support the model derived for sedimentation and diffusion. Additionally, the relation between δand D derived in chapter 2 is validated. Particles larger than a few tenths of a micron are removed by sedimentation; particles smaller than about 0.1 μm aresubject to diffusive deposition, though often electrophoresis plays an important role (particularly, in case of particles of about 0.1 μm). It is shown that aerosol measurements in containments can be used for determination of dynamic shape factors and aerodynamic diameters.Aerosols in heated dry containments are removed by thermophoresis. Observations on a large variety of aerosols and enclosures are in fair agreement with the model on thermophoretic removal derived in chapter 2. Interpretation of the experimental results yields the thermophoretic properties of aerosols. The results support the theories of Brock and Stetter, and are in disagreement with those of Derjaguin and Epstein. In accordance with theoretical predictions, thermophoretic decay constants are obtained independent of particle size (≥0.5 μm), of particle material and of temperature. Gentle heating of the floor of a containment is shown to have a stabilizing effect on the enclosed aerosol.Introduction of aerosol in a containment with a heated pool of liquid on the floor leads to particle growth by vapour condensation followed by an accelerating removal by sedimentation. Experimental observations support a model describing aerosol behaviour in such systems. The knowledge of this aerosol behaviour allows study of condensation on aerosol particles and particle growth under conditions of variable degrees of supersaturation. The degree of supersaturation can be varied by means of the heating power dissipated in the pool of liquid as well as by means of solving substances in the liquid.Investigations of aerosol behaviour in photochemical smog chambers show insignificant deposition due to thermophoresis or photophoresis under these conditions. Observed aerosol stabilities could be explained by electrophoretic deposition, yielding a coherent picture with electrophoresis in other investigations. Coagulation constants of aerosol could be calculated from measurements on number concentrations of aerosols in enclosed spaces. The results obtained agree fairly well with Davies' theory on coagulation. Decay curves of number concentration of aerosols in metal vessels can be used for assessment of diffusion coefficients.

In this dissertation a laboratory study dealing with the atmospheric chemistry of NO 2 -O 3 systems is described. Knowledge of this system is relevant for a better understanding of a number of air pollution problems, particularly that of acid deposition.In chapter 1 a short overview of atmospheric chemistry is given, in which the formation of oxidants, the SO 2 chemistry and the NO X chemistry are considered.It appears that, in absence of light, interactions between NO 2 and O 3 may lead to the formation of nitric acid. After oxidation of NO 2 by O 3 , the NO 3 radical is formed. Next, this radical can react in several ways. one of the possibilities is the reaction with NO 2 resulting in N 2 O 5 . The actual nitric acid formation is the N 2 O 5 hydrolysis. In theory, this process can substantially contribute to the nitric acid formation In the atmosphere. Some gaps in the present knowledge are the exact mechanism and kinetics of the N 2 O 5 hydrolysis and the NO 3 reactivity.Chapter 2 contains a review of the recent literature. Subsequently, laboratory, field and model studies are considered. Without doubt, it can be concluded that the non-photochemical nitrate formation by the NO 2 -O 3 system is recognized as an important atmospheric chemical process. The above-mentioned knowledge gaps are confirmed which, among other things. follows from measurements of the ambient NO 3 radical concentration profile. Regularly, it is suggested that heterogeneous processes of NO 3 or N 2 O 5 removal are involved. The parameters needed to quantify such processes are currently unavailable.After the general Introduction and the literature review, the experimental methods applied in the present investigation are described. The construction of the employed laboratory equipment is given. The basic principles of the techniques used for the generation and analysis of the reactants are listed.In the chapters 4 to 7 the results are described and discussed. Chapter 4 treates the results of a study on the NO 2 -O 3 chemistry at sub-ppm concentrations as well as the influence of temperature and relative humidity (R.H.). The experiments are performed using the standard techniques for measurement and calibration of NO 2 and O 3 .If we consider the stoichiometry of the reaction system at R.H. < 0.1%, It appears that it deviates from the theoretical value of two. Obviously a side-reaction, that regenerates NO 2 , consumes extra O 3 or both, is involved. Since the stoichiometry significantly differs in reaction vessels of different size (other variables constant), we have to deal with a wall reaction. Further analysis of the results combined with literature data leads to the interpretation that the low stoichiometry is caused by the heterogeneous NO 3 decay on the vessel wall with regeneration of NO 2 , With this reaction mechanism, kinetic parameters can be obtained from the massbalance of every component. The rate constant of the NO 2 -O 3 reaction appears to agree reasonably well with literature values.The influence of R.H. results in an increase of the stoichiometry caused by N 2 O 5 hydrolysis. The kinetics of the NO 2 -O 3 reaction remains unchanged. The kinetics of the N 2 O 5 hydrolysis can be described with Its pseudo-first-order rate constant. This rate constant Is not directly proportional to the R. H. , which is an indication that the N 2 O 5 hydrolysis -at least in part- occurs heterogeneously at the wall of the reaction vessel.In the atmosphere, aerosol particles are involved in these heterogeneous processes. Before studying the NO 2 -O 3 -aerosol chemistry, the dynamical behaviour of aerosol particles in the reaction vessels is considered. The results are given in chapter 5. The differences in the particle number concentration and in the particle size distribution of the feed and steady state aerosol have been measured. It appears that these differences are caused by coagulation and wall deposition processes.The influence of aerosol particles on the NO 2 -O 3 chemistry is the subject of chapter 6. 'Dry' aerosol (NaCl; R.H.=15%) and 'wet' aerosol (MgCl 2 ; R.H.=78%) are distinguished. In case of a 'dry' aerosol a small decrease in the stoichiometry is observed. This can be interpreted as a NO 3 decay on the aerosol surface. In case of 'wet' aerosol NO 3 decay as well as N 2 O 5 hydrolysis is important. This follows from the nearly constant stoichiometry and the nitrate formation in the aerosol.The kinetics of the NO 2 -O 3 reaction do not change in the presence of aerosol particles. Moreover, the rate constants of the heterogeneous reactions can be obtained. From these the so- called 'accommodation coefficient' can be deduced. This coefficient Indicates what part of the gas- aerosol collisions really leads to reaction and characterizes the rate of the heterogeneous reaction. The heterogeneous N 2 O 5 hydrolysis can also be understood as a bulk aqueous phase process. The product of Henry's law constant and the rate constant of the aqueous phase hydrolysis can be found. It appears that for N 2 O 5 this product is in fairly good agreement with the product for N 2 O 3 and N 2 O 4 .In chapter 7 the aqueous phase chemistry of NO 2 and O 3 is considered. It is investigated using a gas-liquid contact reactor and analysis of the nitrite and nitrate formation. The results of the Interaction between NO 2 and liquid water are in agreement with the current literature. The influence of O 3 is restricted to the oxidation of nitrite. From the results it can be deduced that aqueous phase NO 2 -O 3 reactions do not significantly contribute to atmospheric nitrate formation.Finally, a general evaluation is given in chapter 8. It can be concluded that this investigation confirms the present insights in the atmospheric chemistry of NO 2 and O 3 and that new insights in the reactivity of NO 3 and N 2 O 5 are obtained.

Verslag wordt gedaan van een bezoek aan Pfizer GMBH Karlsruhe met gesprek en demonstratie van meetapparatuur. Tevens wordt een waardeoordeel gegeven over deze wijze van stofbestrijding.

Different processes can influence the perticle size distribution of fresh automobile aerosols. Dispersion, deposition and polydispers coagulation according to Fuchs (1964) are discussed. The monodispers coagulation theory of Davies (1979) and the formula describing the gradient coagulation are extended to polydispers aerosols. Also a critical review is given of the behavious of submicron particles under the influence of the relative humidity and the reentrainment of these particles by tubulence.A survey is given of the electrical aerosolanalyzer and condensation nucleus counter. The control and comparison of these instruments is treated next. After that a literature review of the particle size distributions of traffic aerosols and the emissions which can be calculated from these distributions is presented.The emission in particles/km per vehicle can be derived from the size distribution measurements of aerosols and tracergas concentrations along a road, because the dispersion is known for the tracergas. As the aerosol samples were taken at different distances from the road, with different residence times, the velocity of coagulation and deposition can be deduced. Also one model is used to describe the three processes dispersion, deposition and coagulation. With the measurements along a road an experimental verification of this model was possible.The measured particle size distributions in a tunnel were a steady state concentration. The loss of aerosol bij dispersion, deposition and coagulation is compensated by the traffic emission. With this steady state concentration and the emission by traffic found during the roadexperiments the coagulation constant of submicron particles can be calculated. As a conclusion from these calculations a preference can be given to the theory of DAVIES (1979) above the theory of FUCHS (1964) describing the value of the coagulation constant. With a model that describes the steady state concentration in the tunnel as a function of the emission and removal mechanisms the traffic emission in the tunnel could be calculated.The emissions from the road and tunnel experiments have been evaluated and are in a reasonable agreement. The following emission in particles per vehicle is presented with a variation coefficient between 20% for the bigger particles and 70% for particles of 0.01 μm

Op het Proefstation voor de Varkenshouderij is gedurende een jaar de stallucht van één mestvarkensafdeling met behulp van een biobed gezuiverd. Onder de op het Proefstation geldende omstandigheden werd voor de NH3- emissie een reductie van 85% en voorde emissie van stankstoffen een reductie van 75% bereikt.