Dissertations / Theses: 'Atmospheric aerosol formation'

1

Tasoglou, Antonios. "Formation and Chemical Aging of Atmospheric Carbonaceous Aerosol." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/757.

Full text

Abstract:

Atmospheric aerosols can cause serious human health problems and are also affecting the energy balance of our planet contributing to climate change. Organic aerosol (OA) is the most diverse and least understood component of submicron aerosols, in part because of a wide variety of biogenic and anthropogenic sources as well as contributions from both direct emission and secondary formation in the atmosphere. Air quality models often seriously under-predict the concentration of OA in the atmosphere due mainly to our lack of understanding of the atmospheric chemical and physical processing of the emitted organic compounds. A series of experimental studies were performed to address some of the major questions regarding atmospheric OA. In the first phase of the work, the secondary organic aerosol (SOA) production during the oxidation of β-caryophyllene by ozone (O3) and hydroxyl radicals (OH) and the subsequent chemical aging of the products during reactions with OH were investigated. Experiments were conducted with ozone, hydroxyl radicals at low NOx (zero added NOx) and at high NOx (100s of ppb). The SOA mass yield at 10 μg m-3 of organic aerosol was 27% for the ozonolysis, 20% for the reaction with OH at low NOx and 38% at high NOx under dry conditions, 20oC, and ozone excess. Parameterizations of the fresh SOA yields have been developed. The average fresh SOA atomic O:C ratio varied from 0.24 to 0.34 depending on the oxidant and the NOx level, while the H:C ratio was close to 1.5 for all systems examined. An average density of 1.06±0.1 μg m-3 of the β-caryophyllene SOA was estimated. The exposure to UV-light had no effect on the β-caryophyllene SOA concentration and Aerosol Mass Spectrometer (AMS) mass spectrum. The chemical aging of the produced β-caryophyllene SOA was studied by exposing the fresh SOA to high concentrations (107 molecules cm-3) of OH for several hours. These additional reactions ii increased the SOA concentration by 15-40% and the O:C by approximately 25%. A limited number of experiments suggested that there was a significant impact of the relative humidity on the chemical aging of the SOA. The evaporation rates of β-caryophyllene SOA were quantified by using a thermodenuder allowing us to estimate the corresponding volatility distributions and effective vaporization enthalpies. In the second step the accuracy of continuous black carbon measurements of a series of commercially available instruments was assessed for biomass burning particulate matter. Black carbon-containing particles are the most strongly light absorbing aerosols in the atmosphere. They are emitted during the combustion of fossil fuels, biofuels, and biomass. Measurements of black carbon are challenging because of its semi-empirical definition based on physical properties and not chemical structure, the complex and continuously changing morphology of the corresponding particles, and the effects of other particulate components on its absorption. In this study we compare six available commercial continuous BC instruments using biomass burning aerosol. The comparison involves a Soot Particle Aerosol Mass Spectrometer (SP-AMS), a Single Particle Soot Photometer (SP2), an aethalometer, a Multiangle Absorption Photometer (MAAP), and a blue and a green photoacoustic extinctiometer (PAX). An SP-AMS collection efficiency equal to 0.35 was measured for this aerosol system. The SP-AMS was then compared to all the other commercial instruments. Two regimes of behavior were identified corresponding to high and low organic/black carbon ratio. New mass absorption cross sections (MAC) were calculated for the optical instruments for the two regimes. The new MAC values varied from 30% to 2.3 times the instrument default values depending on the instrument and the regime. This comparison of the optical instruments suggests a stronger discrepancy among the BC measurements as the organic carbon content of the BC-containing particles increases. In the next step we focused on the chemical aging of combustion emissions. Smog chamber experiments were conducted to study the changes of the physical properties and chemical composition of biomass burning particles as they evolve in the atmosphere. A Soot Particle Aerosol Mass Spectrometer (SP-AMS) and a Single Particle Soot Photometer (SP2) were used for the chemical characterization of the particles. An Aethalometer as well as a green and a blue photoacoustic extinctiometer (PAX) were used for the study of the aerosol optical properties. As the biomass burning smoke aged, exposed to UV light, ozone, or OH radicals, organic material condensed on the preexisting particles. This coating led to an increase of the absorption of the black carbon-containing particles by as much as a factor of two. The absorption enhancement of biomass burning particles due to their coating with aromatic secondary organic aerosol (SOA) was also studied. The resulting absorption enhancement was determined mainly by the changes in the SOA mass concentration and not the changes of its oxidation state. The enhancement of the absorption of the aging biomass burning particles was consistent with the predictions of a core-shell Mie theory model assuming spherical particles and non-absorbing coating. In the last phase of the work emissions from cooking activities were studied. Cooking organic aerosol (COA) is a significant fraction of the total fine aerosol in urban areas around the world. COA chemical aging experiments took place in a smog chamber in the presence of UV light or in excess of ozone. Positive matrix factorization was used to characterize the changes in the chemical composition of the COA during the chemical aging. The chemical composition of the produced aged COA was similar for both aging methods The chemical aging processes cause an increase of the organic mass and its oxidation state. The fresh COA particles have a low CCN activity but their activity increases significantly as they chemically age.

APA, Harvard, Vancouver, ISO, and other styles

2

Wang, Shih-chen Flagan Richard C. "Aerosol formation and growth in atmospheric organic/NOx systems /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-01112007-152148.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Hennigan, Christopher James. "Properties of secondary organic aerosol in the ambient atmosphere sources, formation, and partitioning /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26598.

Full text

Abstract:

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Weber, Rodney; Committee Co-Chair: Bergin, Michael; Committee Member: Mulholland, James; Committee Member: Nenes, Athanasios; Committee Member: Russell, Armistead. Part of the SMARTech Electronic Thesis and Dissertation Collection.

APA, Harvard, Vancouver, ISO, and other styles

4

Lack, Daniel Anthony. "Modelling the formation of atmospheric aerosol from gaseous organic precursors." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15831/1/Daniel_Lack_Thesis.pdf.

Full text

Abstract:

This thesis describes the investigation of three aspects of the formation of secondary organic aerosol (SOA): * Aerosol formation from mixed precursors * Global modelling of SOA formation * Modelling of dynamics of SOA formation based on empirical data collected from smog chamber experiments. The formation and growth processes of secondary organic aerosol were investigated using smog chamber experimentation and modelling techniques to gain a better understanding of the application of SOA yield values in modelling both SOA mass and dynamics. Published SOA yields from a range of volatile organic compounds (VOCs) are used to model SOA mass on a local, regional or global scale, based on the assumption that the SOA yield of a mixture is the sum of the yields of the components. Experimental investigations into SOA yield from mixtures of VOC revealed potential uncertainties that would result from applying these yields to systems containing multiple VOCs. SOA formation in systems of toluene or m-xylene, compared with systems of these VOCs and propene, have shown that the introduction of propene (which has a zero SOA yield) to smog chamber photo-oxidations of toluene or m-xylene delays the formation and suppresses the overall yield of SOA from 450 to 90 µg m-3 ppm-1 for the toluene system and from 325 to 125 µg m-3 ppm-1 for the mvxylene system compared with systems of individual species without propene. The SOA partitioning yield data also indicates that partitioning of species to existing aerosol is suppressed in the mixed systems. Gas-phase modelling of these experiments showed that potential SOA species were expected to be formed sooner due to the increased system reactivity provided by propene. The observed delay in SOA nucleation, similar consumption rates of toluene and m-xylene in both the single and mixed systems and the gas-phase modelling results suggest that the addition of propene to hydrocarbon SOA systems modifies the gas-phase chemistry leading to the formation of potential SOA species from toluene and m-xylene. This result calls into question the bulk and partitioning yield values that have been published for pure substances as well as the validity of applying individual VOC yields to VOC mixture. Application of SOA yields to the global scale provides estimates of annual global SOA formation, global contributions from various VOCs and regional SOA distributions. Two SOA modules, using bulk and partitioning yield methods, were added to a global atmospheric chemical transport model, MOZART-2. The bulk yield method, representing the maximum possible global SOA burden, gave an annual production of 24.5 Tg of SOA, which is slightly lower than previous estimates (30 - 270 Tg yr-1). The partitioning method, which gives a more realistic estimate of SOA formation, produced 15.3 Tg yr-1; the biogenic fraction (13.6 Tg yr-1) compares to a previous estimate of biogenic SOA of 18.5 Tg yr-1 and 2.5 to 44 Tg yr- 1 using the partitioning method. Anthropogenic SOA contributions of 1.1 Tg yr-1 from MOZART-2 compared to recent estimates of 0.05 -2.62 Tg yr-1. SOA production was found to be dependent on oxidant availability and VOC emissions in South America and Asia. The partitioning method produced significantly less SOA due to limited availability of OC. Thepartitioning method also produced a peak SOA concentration of 10 µg m-3 over South America in September and showed that SOA is at maximum production for most of the year in Asia and Europe. The two SOA formation methods also provides data to analyse the restrictions to SOA formation in particular regions, based on the maximum amount of SOA able to form (bulk yield method) and the more realistic partitioning estimate from the same region. Limitations to SOA formation in a particular region can be attributed to deficiencies in OC availability or VOC oxidant concentrations. Comparisons to limited observational and modelled data suggest that the MOZART-2 SOA model provides a good representation of global averaged SOA. SOA mass concentrations, predicted by models such as MOZART-2, can be used in part to model the dynamics of an SOA population (e.g. size of particles, number concentrations etc.). Aerosol properties such as size and number concentration can then be used to estimate their effect on climate and health. The explicit representation of the processes that affect aerosol dynamics, such as nucleation, condensation, evaporation and coagulation can be complex and use significant computational resources. Simplification of the discrete coagulation equation and empirical coagulation coefficients for continuum and non-continuum regime diffusion kinetics provided a simplified method of coagulation capable of predicting the evolution of inert sodium chloride aerosol in chamber experiments. A variable coagulation coefficient (linked to the mean particle number concentration of each experiment) was developed. This method is an empirical surrogate for the standard coefficient corrections applied to Brownian based diffusion in the continuum regime to account for the different kinetic effects within the transition and free molecular diffusion regimes. This method removes the need for calculating individual coefficients for each particle interaction. Estimates of modeluncertainty show that within uncertainty limits the model provides a good representation of experimental data. Correlation and index of agreement (IOA) calculations revealed good statistical agreement between modelled and experimental. Some experiments showed degrees of coagulation under prediction using the variable coefficient technique. Investigations into the effect of aerosol type and size, temperature and humidity may be necessary to refine the variable coefficient calculation technique. The model showed little sensitivity to model time step and is capable of high resolution representation of the aerosol. Mass concentration is conserved within the model whereas some error due to numerical diffusion within the number concentrations results from the bin sectioning technique used. The simplicity of this sectioning method over other methods and the minimal effect of numerical diffusion establishes a simplified method of modelling relative to the high resolution of the aerosol distribution the model achieves. It is suggested that the efficiency improvements introduced by the approaches used in developing this model provide an efficient ultra-fine coagulation modelling for atmospheric models. A semi-empirical model for SOA dynamics (SPLAT) incorporating coagulation, nucleation, condensation and evaporation was developed. The aim of the model and the development process was to predict, with high resolution and minimal computational expense, the formation and growth of SOA given a SOA mass input as a function of time. The average size distribution profile from chamber experimental data was used as part of the nucleation module. This technique provided an alternative method of representing the particle distribution compared to those models that assume a single diameter of nucleated particle or a fixed log-normal mode for the entire evolution of SOA. All SPLAT simulations assume organic nucleation events within the experiments modelled, although it is stilluncertain whether they occur in the atmosphere. The modelled nucleation events have produced a single nucleation burst, a result of immediate domination of condensation as soon as nucleation occurs. This deficiency is likely to be a result of the assumption of free molecular diffusion for condensation. The rate of condensation, calculated at every time step, is based on the aerosol size distributed surface area and the particle-size-dependent saturation mass concentrations. The SPLAT coagulation module was a version of the model developed in Chapter 6. Comparisons between experimental and modelled data showed good agreement. These comparisons revealed the shortcomings in the nucleation module while a statistical analysis of the modelled and experimental data has shown SPLAT to be effective in modelling a range of SOA systems. The complexity introduced in modelling aerosol dynamics in high resolution is offset in SPLAT by efficiency improvements due to the insensitivity of the model to time step size and simplified methods of bin sectioning, nucleation, coagulation, condensation and evaporation. Published SOA yields can be applied to predict SOA mass at local, regional or global scales. Although previously unreported uncertainties in these yields have been shown to exist, the MOZART-2 global chemical transport model has shown that SOA mass concentration can be predicted with reasonable quality, considering the scale of the model and limited observational data. These global scale SOA mass predictions can be used purely for global burden and occurrence, or as the input for modelling the dynamics of an aerosol population, which is significant for estimating an aerosol population's effect on climate change and health. SOA mass concentrations from chamber experiments were used as input to a SOA dynamics model. This model (SPLAT) then predicted the evolution of particle number concentrations and size within these experiments based on this mass input. Application of the dynamics model to the output of the MOZART-2 model could then provide a comprehensive global scale SOA modelling package.

APA, Harvard, Vancouver, ISO, and other styles

5

Lack, Daniel Anthony. "Modelling the Formation of Atmospheric Aerosol From Gaseous Organic Precursors." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15831/.

Full text

Abstract:

This thesis describes the investigation of three aspects of the formation of secondary organic aerosol (SOA): * Aerosol formation from mixed precursors * Global modelling of SOA formation * Modelling of dynamics of SOA formation based on empirical data collected from smog chamber experiments. The formation and growth processes of secondary organic aerosol were investigated using smog chamber experimentation and modelling techniques to gain a better understanding of the application of SOA yield values in modelling both SOA mass and dynamics. Published SOA yields from a range of volatile organic compounds (VOCs) are used to model SOA mass on a local, regional or global scale, based on the assumption that the SOA yield of a mixture is the sum of the yields of the components. Experimental investigations into SOA yield from mixtures of VOC revealed potential uncertainties that would result from applying these yields to systems containing multiple VOCs. SOA formation in systems of toluene or m-xylene, compared with systems of these VOCs and propene, have shown that the introduction of propene (which has a zero SOA yield) to smog chamber photo-oxidations of toluene or m-xylene delays the formation and suppresses the overall yield of SOA from 450 to 90 µg m-3 ppm-1 for the toluene system and from 325 to 125 µg m-3 ppm-1 for the mvxylene system compared with systems of individual species without propene. The SOA partitioning yield data also indicates that partitioning of species to existing aerosol is suppressed in the mixed systems. Gas-phase modelling of these experiments showed that potential SOA species were expected to be formed sooner due to the increased system reactivity provided by propene. The observed delay in SOA nucleation, similar consumption rates of toluene and m-xylene in both the single and mixed systems and the gas-phase modelling results suggest that the addition of propene to hydrocarbon SOA systems modifies the gas-phase chemistry leading to the formation of potential SOA species from toluene and m-xylene. This result calls into question the bulk and partitioning yield values that have been published for pure substances as well as the validity of applying individual VOC yields to VOC mixture. Application of SOA yields to the global scale provides estimates of annual global SOA formation, global contributions from various VOCs and regional SOA distributions. Two SOA modules, using bulk and partitioning yield methods, were added to a global atmospheric chemical transport model, MOZART-2. The bulk yield method, representing the maximum possible global SOA burden, gave an annual production of 24.5 Tg of SOA, which is slightly lower than previous estimates (30 - 270 Tg yr-1). The partitioning method, which gives a more realistic estimate of SOA formation, produced 15.3 Tg yr-1; the biogenic fraction (13.6 Tg yr-1) compares to a previous estimate of biogenic SOA of 18.5 Tg yr-1 and 2.5 to 44 Tg yr- 1 using the partitioning method. Anthropogenic SOA contributions of 1.1 Tg yr-1 from MOZART-2 compared to recent estimates of 0.05 -2.62 Tg yr-1. SOA production was found to be dependent on oxidant availability and VOC emissions in South America and Asia. The partitioning method produced significantly less SOA due to limited availability of OC. Thepartitioning method also produced a peak SOA concentration of 10 µg m-3 over South America in September and showed that SOA is at maximum production for most of the year in Asia and Europe. The two SOA formation methods also provides data to analyse the restrictions to SOA formation in particular regions, based on the maximum amount of SOA able to form (bulk yield method) and the more realistic partitioning estimate from the same region. Limitations to SOA formation in a particular region can be attributed to deficiencies in OC availability or VOC oxidant concentrations. Comparisons to limited observational and modelled data suggest that the MOZART-2 SOA model provides a good representation of global averaged SOA. SOA mass concentrations, predicted by models such as MOZART-2, can be used in part to model the dynamics of an SOA population (e.g. size of particles, number concentrations etc.). Aerosol properties such as size and number concentration can then be used to estimate their effect on climate and health. The explicit representation of the processes that affect aerosol dynamics, such as nucleation, condensation, evaporation and coagulation can be complex and use significant computational resources. Simplification of the discrete coagulation equation and empirical coagulation coefficients for continuum and non-continuum regime diffusion kinetics provided a simplified method of coagulation capable of predicting the evolution of inert sodium chloride aerosol in chamber experiments. A variable coagulation coefficient (linked to the mean particle number concentration of each experiment) was developed. This method is an empirical surrogate for the standard coefficient corrections applied to Brownian based diffusion in the continuum regime to account for the different kinetic effects within the transition and free molecular diffusion regimes. This method removes the need for calculating individual coefficients for each particle interaction. Estimates of modeluncertainty show that within uncertainty limits the model provides a good representation of experimental data. Correlation and index of agreement (IOA) calculations revealed good statistical agreement between modelled and experimental. Some experiments showed degrees of coagulation under prediction using the variable coefficient technique. Investigations into the effect of aerosol type and size, temperature and humidity may be necessary to refine the variable coefficient calculation technique. The model showed little sensitivity to model time step and is capable of high resolution representation of the aerosol. Mass concentration is conserved within the model whereas some error due to numerical diffusion within the number concentrations results from the bin sectioning technique used. The simplicity of this sectioning method over other methods and the minimal effect of numerical diffusion establishes a simplified method of modelling relative to the high resolution of the aerosol distribution the model achieves. It is suggested that the efficiency improvements introduced by the approaches used in developing this model provide an efficient ultra-fine coagulation modelling for atmospheric models. A semi-empirical model for SOA dynamics (SPLAT) incorporating coagulation, nucleation, condensation and evaporation was developed. The aim of the model and the development process was to predict, with high resolution and minimal computational expense, the formation and growth of SOA given a SOA mass input as a function of time. The average size distribution profile from chamber experimental data was used as part of the nucleation module. This technique provided an alternative method of representing the particle distribution compared to those models that assume a single diameter of nucleated particle or a fixed log-normal mode for the entire evolution of SOA. All SPLAT simulations assume organic nucleation events within the experiments modelled, although it is stilluncertain whether they occur in the atmosphere. The modelled nucleation events have produced a single nucleation burst, a result of immediate domination of condensation as soon as nucleation occurs. This deficiency is likely to be a result of the assumption of free molecular diffusion for condensation. The rate of condensation, calculated at every time step, is based on the aerosol size distributed surface area and the particle-size-dependent saturation mass concentrations. The SPLAT coagulation module was a version of the model developed in Chapter 6. Comparisons between experimental and modelled data showed good agreement. These comparisons revealed the shortcomings in the nucleation module while a statistical analysis of the modelled and experimental data has shown SPLAT to be effective in modelling a range of SOA systems. The complexity introduced in modelling aerosol dynamics in high resolution is offset in SPLAT by efficiency improvements due to the insensitivity of the model to time step size and simplified methods of bin sectioning, nucleation, coagulation, condensation and evaporation. Published SOA yields can be applied to predict SOA mass at local, regional or global scales. Although previously unreported uncertainties in these yields have been shown to exist, the MOZART-2 global chemical transport model has shown that SOA mass concentration can be predicted with reasonable quality, considering the scale of the model and limited observational data. These global scale SOA mass predictions can be used purely for global burden and occurrence, or as the input for modelling the dynamics of an aerosol population, which is significant for estimating an aerosol population's effect on climate change and health. SOA mass concentrations from chamber experiments were used as input to a SOA dynamics model. This model (SPLAT) then predicted the evolution of particle number concentrations and size within these experiments based on this mass input. Application of the dynamics model to the output of the MOZART-2 model could then provide a comprehensive global scale SOA modelling package.

APA, Harvard, Vancouver, ISO, and other styles

6

Matsunaga, Aiko. "Secondary organic aerosol formation from radical-initiated reactions of alkenes development of mechanisms /." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1899476651&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1269361334&clientId=48051.

Full text

Abstract:

Thesis (Ph. D.)--University of California, Riverside, 2009.
Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 10, 2010). Includes bibliographical references. Also issued in print.

APA, Harvard, Vancouver, ISO, and other styles

7

Barahona, Donifan. "On the representation of aerosol-cloud interactions in atmospheric models." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41169.

Full text

Abstract:

Anthropogenic atmospheric aerosols (suspended particulate matter) can modify the radiative balance (and climate) of the Earth by altering the properties and global distribution of clouds. Current climate models however cannot adequately account for many important aspects of these aerosol-cloud interactions, ultimately leading to a large uncertainty in the estimation of the magnitude of the effect of aerosols on climate. This thesis focuses on the development of physically-based descriptions of aerosol-cloud processes in climate models that help to address some of such predictive uncertainty. It includes the formulation of a new analytical parameterization for the formation of ice clouds, and the inclusion of the effects of mixing and kinetic limitations in existing liquid cloud parameterizations. The parameterizations are analytical solutions to the cloud ice and water particle nucleation problem, developed within a framework that considers the mass and energy balances associated with the freezing and droplet activation of aerosol particles. The new frameworks explicitly account for the impact of cloud formation dynamics, the aerosol size and composition, and the dominant freezing mechanism (homogeneous vs. heterogeneous) on the ice crystal and droplet concentration and size distribution. Application of the new parameterizations is demonstrated in the NASA Global Modeling Initiative atmospheric and chemical and transport model to study the effect of aerosol emissions on the global distribution of ice crystal concentration, and, the effect of entrainment during cloud droplet activation on the global cloud radiative properties. The ice cloud formation framework is also used within a parcel ensemble model to understand the microphysical structure of cirrus clouds at very low temperature. The frameworks developed in this work provide an efficient, yet rigorous, representation of cloud formation processes from precursor aerosol. They are suitable for the study of the effect of anthropogenic aerosol emissions on cloud formation, and can contribute to the improvement of the predictive ability of atmospheric models and to the understanding of the impact of human activities on climate.

APA, Harvard, Vancouver, ISO, and other styles

8

James, Jonathan David. "Investigation into the composition and formation of atmospheric aerosol over the north-east Atlantic Ocean." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324171.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Zhang, Xiaolu. "The sources, formation and properties of soluble organic aerosols: results from ambient measurements in the southeastern united states and the los angeles basin." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44894.

Full text

Abstract:

900 archived FRM filters from 15 sites over the southeast during 2007 were analyzed for PM2.5 chemical composition and physical properties. Secondary components (i.e. sulfate aerosol and SOA) were the major contributors to the PM2.5 mass over the southeast, whereas the contribution from biomass burning varied with season and was negligible (2%) during summer. Excluding biomass burning influence, FRM WSOC was spatially homogeneous throughout the region, similar to sulfate, yet WSOC was moderately enhanced in locations of greater predicted isoprene emissions in summer. On smaller spatial scale, a substantial urban/rural gradient of WSOC was found through comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008, indicating important contribution from anthropogenic emissions. A comparative study between Atlanta and LA reveals a number of contrasting features between two cities. WSOC gas-particle partitioning, investigated through the fraction of total WSOC in the particle phase, Fp, exhibited differing relationships with ambient RH and organic aerosols. In Atlanta, both particle water and organic aerosol (OA) can serve as an absorbing phase. In contrast, in LA the aerosol water was not an important absorbing phase, instead, Fp was correlated with OA mass. Fresh LA WSOC had a consistent brown color and a bulk absorption per soluble carbon mass at 365 nm that was 4 to 6 times higher than freshly-formed Atlanta soluble organic carbon. Interpreting soluble brown carbon as a property of freshly-formed anthropogenic SOA, the difference in absorption per carbon mass between the two cities suggests most WSOC formed within Atlanta is not from an anthropogenic process similar to LA.

APA, Harvard, Vancouver, ISO, and other styles

10

Malloy, Quentin Gerald James. "Chemical and physical characterization of secondary organic aerosol formation from select agricultural emissions." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?index=33&did=1871857121&SrchMode=1&sid=2&Fmt=7&retrieveGroup=0&VType=PQD&VInst=PROD&RQT=309&VName=PQD&TS=1270140114&clientId=48051.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Marks, Marguerite Colasurdo. "Incorporating Chemical Activity and Relative Humidity Effects in Regional Air Quality Modeling of Organic Aerosol Formation." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1511.

Full text

Abstract:

Atmospheric particulate matter is known to have significant effects on human health, visibility, and global climate. The magnitudes of these effects, however, depend in complex ways on chemical composition, relative humidity, temperature, phase state, and other parameters. Current regional air quality models such as CMAQ (Community Multiscale Air Quality model) ignore many of these considerations, and consider that the formation of secondary organic aerosol (SOA) can be calculated by assuming thermodynamic ideality in the organic particulate matter (OPM) phase as well as negligible uptake of water into the OPM phase. Theoretical predictions and model simulations considering non-ideality and water uptake show that the standard model assumptions can lead to large errors in predicted SOA mass, and that the magnitude of these errors is sensitive to the composition of the OPM phase. The SOA module in CMAQ v4.7.1 has been revised in this work to allow consideration of the effects of both non-ideality and water uptake. First, a reasonable specific surrogate structure was assigned to each of the lumped products assumed to be produced by reaction of the different precursor hydrocarbons considered in CMAQ (e.g., isoprene, benzene, and toluene). Second, the CMAQ code was modified to allow iterative calculation (at each point in space and time) of the gas/particle partitioning coefficient for each of the SOA-forming products and for water. Third, model simulations were performed for the Eastern US at a resolution of 36-km x 36-km for late summer 2006, under a range of relative humidity conditions. When compared with an appropriate base case, the modified code produced increases in SOA ranging from 0.17 to 0.51 micrograms per cubic meter. The average change was 0.30 micrograms per cubic meter, corresponding to a 37% increase in SOA formation. Incorporation of phase separation effects would likely lead to further increases in predicted SOA levels.

APA, Harvard, Vancouver, ISO, and other styles

12

Capouet, Manuel J. F. "Modeling the oxidation of alpha-pinene and the related aerosol formation in laboratory and atmospheric conditions." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210935.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Gonser, Stefan Georg [Verfasser], and Andreas [Akademischer Betreuer] Held. "Ion dynamics and aerosol mass spectrometry during atmospheric new particle formation / Stefan Georg Gonser. Betreuer: Andreas Held." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1060010216/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Padro, Martinez Luz Teresa. "Towards an understanding of the cloud formation potential of carbonaceous aerosol laboratory and field studies /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31780.

Full text

Abstract:

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Nenes, Athanasios; Committee Member: Huey, Greg; Committee Member: Meredith, Carson; Committee Member: Teja, Amyn; Committee Member: Weber, Rodney J. Part of the SMARTech Electronic Thesis and Dissertation Collection.

APA, Harvard, Vancouver, ISO, and other styles

15

Clark, Jared M. "The Formation and Stability of Radical-Molecule and Radical-Radical Complexes and Their Importance in Atmospheric Processes." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2679.

Full text

Abstract:

This research explores the role that radical-molecule complexes play in the chemistry of Earth's atmosphere. The formation of such complexes can have direct and pronounced effects on the reaction and product outcome of atmospheric chemical reactions. Some attention is also given to the formation of radial-radical pre-reactive complexes in the HO + ClO system. Peroxy radicals (RO2) can form stable complexes with polar compounds such as H2O, NH3, and CH3OH. For the simplest RO2 radical, HO2, complex formation (e.g., HO2-H2O, HO2-NH3, and HO2-722;CH3OH) gives rise to a significant increase in the HO2 self-reaction rate constant. Although this phenomenon has been observed since the mid-1970s, no satisfactory explanation has been put forward to explain this effect. Herein a rationale for the enhancement of the HO2 self-reaction is given based on extensive geometric, mechanistic and natural bond orbital (NBO) analyses. The apparent lack of a rate enhancement for the methyl peroxy (CH3O2) self-reaction is also presented. The combined insights gained from these two systems are then extended to predict if a water enhancement is expected for the 2-hydroxyethyl peroxy (HOCH2CH2O2) self-reaction kinetics. The computational results of this study are then compared to experimental work and conclusions are drawn towards a general procedure to predict the presence/absence of water initiated rate enhancements in RO2 systems as a whole. Original work regarding the formation of a series of organic RO2-H2O complexes is presented. This work established the effects of different functional groups on the stability of organic peroxy radicals and makes estimates of the associated atmospheric lifetimes and equilibrium constants. This work is further extended to the family of peroxy radicals that form from the atmospheric oxidation of isoprene (the most abundant non-methane biologically emitted hydrocarbon). For the first time, complexes of isoprene peroxy radicals with water are presented along with atmospheric lifetime estimates. Conclusions are made as to the effect of water on the product branching ratio of the isoprene peroxy radical + NO2. The oxidation of hexanal to form hexanal peroxy radicals is discussed within the context of the formation of hexanal peroxy water complexes.Aerosol formation is also perturbed as a result of complexation. Aerosol formation under atmospheric conditions is hypothesized to be initiated by radical-molecule complex formation. For example, in the absence of ammonia, the nucleation of H2SO4 in water vapor to form sulfuric acid aerosols is slow. However, as the concentration of NH3 rises, a marked increase in the rate of sulfuric acid aerosol formation is observed. This work explores the effects of the photolysis products of NH3 (NH2 and NH) on the rate of aerosol formation in systems involving H2SO4, HNO3, HC(O)OH, and CH3C(O)OH. With the exception of H2SO4-NH3 and HNO3-NH3 (geometries already published in the literature), minimum energy structures are presented here for the first time for each of the acid-NHx complexes. Thermochemical data and lifetime estimates are provided for each complex. Conclusions about the relevance of acid-NH2 and acid-NH in the formation of atmospheric aerosols are set forth. Finally, mechanistic insights into the reaction of the hydroxyl radical (OH) and Cl2O are obtained via analysis of the two potential energy surfaces that both involve the formation of HO-Cl2O pre-reactive complexes.

APA, Harvard, Vancouver, ISO, and other styles

16

Foley, Theresa Anne. "Three Air Quality Studies: Great Lakes Ozone Formation and Nitrogen Dry Deposition; and Tucson Aerosol Chemical Characterization." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/265339.

Full text

Abstract:

The Clean Air Act of 1970 was promulgated after thousands of lives were lost in four catastrophic air pollution events. It authorized the establishment of National Ambient Air Quality Standards or (NAAQS) for six pollutants that are harmful to human health and welfare: carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone and sulfur dioxide. The Clean Air Act also led to the establishment of the United Stated Environmental Protection Agency (US EPA) to set and enforce regulations. The first paper in this dissertation studies ozone in the Lake Michigan region (Foley, T., Betterton, E.A., Jacko, R., Hillery, J., 2011. Lake Michigan air quality: The 1994-2003 LADCO Aircraft Project (LAP). Atmospheric Environment 45, 3192-3202.) The Chicago-Milwaukee-Gary metropolitan area has been unable to meet the ozone NAAQS since the Clean Air Act was implemented. The Lake Michigan Air Directors' Consortium (LADCO) hypothesized that land breezes transport ozone precursor compounds over the lake, where a large air/water temperature difference creates a shallow conduction layer, which is an efficient reaction chamber for ozone formation. In the afternoon, lake breezes and prevailing synoptic winds then transport ozone back over the land. To further evaluate this hypothesis, LADCO sponsored the 1994-2003 LADCO Aircraft Project (LAP) to measure the air quality over Lake Michigan and the surrounding areas. This study has found that the LAP data supports this hypothesis of ozone formation, which has strong implications for ozone control strategies in the Lake Michigan region. The second paper is this dissertation (Foley, T., Betterton, E.A., Wolf, A.M.A., 2012. Ambient PM10 and metal concentrations measured in the Sunnyside Unified School District, Tucson, Arizona. Journal of the Arizona-Nevada Academy of Science, 43, 67-76) evaluated the airborne concentrations of PM10 (particulate matter with an aerodynamic diameter of 10 microns or less) and eight metalloids and metals (arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, and nickel) in the southern Tucson metropolitan area. A Tucson company that uses beryllium oxide to manufacture thermally conductive ceramics has prompted strong citizen concern. This study found that the study area has good air quality with respect to PM₁₀ and metals, with ambient concentrations meeting US Environmental Protection Agency and World Health Organization standards. Beryllium was detected only once (during a dust storm) and was ascribed to naturally-occurring beryllium in the suspended soil. The third paper (to be submitted to the Journal of Great Lakes Research) studies nitrogen dry deposition over Lake Michigan and Lake Superior. Numerous studies have shown that wet and dry deposition of nitrogen has contributed to the eutrophication of coastal waters and declining productivity of marine fisheries. Nitrogen dry deposition over the Great Lakes themselves, as opposed to the shorelines, has not been documented in the peer-reviewed literature. This paper calculates nitrogen dry deposition over Lake Michigan and Lake Superior, using aircraft measurements from the LADCO Aircraft Study, and finds that over-water, nitrogen dry deposition is a significant source of nitrogen to Lake Michigan and Lake Superior.

APA, Harvard, Vancouver, ISO, and other styles

17

Ofner, Johannes [Verfasser], and Cornelius [Akademischer Betreuer] Zetzsch. "Formation of secondary organic aerosol and its processing by atmospheric halogen species – A spectroscopic study / Johannes Ofner. Betreuer: Cornelius Zetzsch." Bayreuth : Universitätsbibliothek Bayreuth, 2011. http://d-nb.info/1015875475/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Toprak, Emre [Verfasser], and S. [Akademischer Betreuer] Norra. "Real Time Detection of Primary Biological Aerosol Particles (PBAP) in the context of atmospheric ice formation / Emre Toprak. Betreuer: S. Norra." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/105695597X/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Katragkou, Eleni. "Aircraft based measurements of atmospheric sulfur dioxide and ground based measurements of gaseous sulfur (VI) in the simulated internal flow of an aircraft engine implications for atmospheric aerosol formation /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969654588.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Allen, Christopher J. T. "Atmospheric mechanisms of central Saharan dust storm formation in boreal summer : observations from the Fennec campaign." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:896c26f3-c7a5-4c93-9e53-69b69b28d1cb.

Full text

Abstract:

In boreal summer, satellite measurements show that the central Sahara is the dustiest region of the planet. However, ground-based observations of the central Sahara have been limited to its outer edges, leaving a void in observations approximately 1 million km² in area. The Fennec Project has been the first campaign to instrument this remote but climatologically important region. This thesis uses these new observations to detect and explain the atmospheric mechanisms that make the central Sahara the summer global dust maximum. Four atmospheric mechanisms are found to cause dust storms in the central Sahara in June 2011 and June 2012. These are cold pool outflows, low-level jets (LLJs), monsoon surges and dry convective plumes. Dust may be emitted locally by these phenomena, or be advected, principally by cold pools. In both field seasons, dust emission by cold pool outflows is the most important dust mechanism, causing roughly half of the total dust loadings at the Fennec supersite of Bordj-Badji Mokhtar (BBM), the closest station to the dust maximum. The second most important mechanism is dust advection by cold pools (roughly 30% dust at BBM), followed by dust emission by monsoon surges, LLJs and finally dry convective plumes (only 2% dust at BBM). Although June 2012 was significantly more dusty than June 2011, the relative importance of the different atmospheric dust mechanisms at BBM did not change. At the automatic weather stations (AWSs) across the remote desert, cold pools and LLJs are by far the most frequently detected atmospheric dust mechanisms. LLJs are particularly common in the Atlantic Inflow in western Mauritania and in the north-easterly Harmattan in western Algeria. Cold pools are much more frequent at BBM, the station under the greatest moist monsoon influence, than at the AWSs to the north. Detection of advected dust is a particular difficulty without dedicated dust-detection instrumentation or human observers (e.g. at the AWSs). Detection of dust emission mechanisms can be very successful with only routine ground observations and satellite measurements, but quantifying the associated dust burden without dedicated dust instruments is problematic. The choice of instrumentation for dust measurement is crucial. Because cold pool outflows - the most important dust mechanism - frequently occur at night or under cloud, sun photometers miss about half of cold pool dust. Lidars have the advantage of providing height resolved dust profiles, but they suffer from attenuation in thick dust. The nephelometer proved to be the most reliable dust instrument. Although LLJs occurred on 21/28 mornings at BBM in June 2011, only five of these jets led to dust emission. Calculations of momentum exchanges through the atmospheric column show that momentum mix-down from the jet core is the cause of dust emission on these occasions, but that the LLJ has to be particularly strong (≥ 16 m s^-1) to result in dust emission at the surface. Met Office Africa-LAM underestimates monsoon LLJ wind profiles and ERA-Interim reanalysis underestimates both monsoon and Harmattan LLJ wind profiles. At the surface, the Met Office Africa-LAM and GLOBAL models significantly underpredict the frequency of observed wind speeds >6 m s^-1. This will cause them to significantly underestimate dust emission, as emission is a threshold process proportional to the cube of wind speed. A particularly interesting implication of the research presented here is that the central Sahara is likely much more dusty than previously thought. This is because almost all of the techniques currently used to study dust in the region are systematically biased to result in underestimates of dust burden. Cold pools are the most important dust mechanism but, since they rarely occur during the daytime or in cloud-free conditions they are often missed by sun photometers. Many will be missed by satellites that cannot retrieve below cloud and satellites that pass over the Sahara in daylight hours (e.g. the A-train). A commonly-used satellite dust detection algorithm often misses dust under moist (i.e. cold pool) conditions. Cold pools cannot be simulated by models without explicit convection, which requires very high spatial resolution. Finally, the numerical models assessed here significantly underpredict the frequency of wind speeds over the dust emission threshold. The Sahara is probably much dustier than current estimates suggest.

APA, Harvard, Vancouver, ISO, and other styles

21

Van, Eijck Anna [Verfasser]. "Atmospheric degradation of reactive biogenic VOCs and their role in aerosol formation: modelling activities, laboratory experiments and field studies in different vegetation zones / Anna Van Eijck." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1109819099/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Riva, Matthieu. "Caractérisation d’une nouvelle voie de formation des aérosols organiques secondaires (AOS) dans l’atmosphère : rôle des précurseurs polyaromatiques." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14942/document.

Full text

Abstract:

Ce travail a pour objectif d'étudier la formation des aérosols organiques secondaires (AOS) formés dans l'atmosphère à partir de l'oxydation en phase gazeuse de composés organiques volatils en présence d’oxydants atmosphériques (ozone, radicaux hydroxyle, chlore et nitrate). Parmi eux, les hydrocarbures aromatiques polycycliques (HAP) ont été proposés comme étant une source potentiellement importante d’AOS d’origine anthropique. Ainsi, l’oxydation de quatre HAP gazeux majoritaires (naphtalène, acénaphtylène, acénaphtène et phénanthrène) en présence des principaux oxydants atmosphériques a été menée afin de déterminer la formation d’AOS. La caractérisation des phases gazeuse et particulaire par spectrométrie de masse et spectroscopie optique a permis d’identifier les principaux produits d’oxydation afin de proposer des mécanismes réactionnels conduisant à la formation d’AOS. Les différents rendements de formation ont également été déterminés dans le but d'évaluer l'impact de l'oxydation des HAP en phase gazeuse comme source d’aérosols. Les expériences ont été conduites en chambres de simulation atmosphérique ainsi qu'en réacteur à écoulement. L'évolution de l'AOS au cours de son vieillissement a également été étudiée pour identifier les différents processus oxydatifs mis en jeu au sein de l'aérosol organique
This work deals with the secondary organic aerosol (SOA) formation from gas phase oxidation of volatile organic compounds in the presence of atmospheric oxidants (ozone, hydroxyl radical, chlorine and nitrate radical). Among them, polycyclic aromatic hydrocarbons (PAHs) have been proposed as an important potential source of anthropogenic SOA. The oxidation of 4 main gaseous PAHs (naphthalene, acenaphthylene, acenaphthene and phenanthrene) in the presence of main atmospheric oxidants has been performed in order to investigate the SOA formation. Characterization of both gas and particulate phases has been carried out using mass spectrometry and optical spectroscopy allowing the identification of products in both phases. Then, chemical mechanisms have been proposed in order to explain SOA formation. SOA yields have been also determined to evaluate the impact of the gas phase oxidation of PAHs in SOA formation. Experiments have been carried out using flow tube and atmospheric simulation chambers. SOA fate has been investigated to determine the different oxidation processes involved in SOA aging

APA, Harvard, Vancouver, ISO, and other styles

23

Modini, Robin Lewis. "Investigation of the effect of organics on the water uptake of marine aerosols." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/46884/1/Robin_Modini_Thesis.pdf.

Full text

Abstract:

Water uptake refers to the ability of atmospheric particles to take up water vapour from the surrounding atmosphere. This is an important property that affects particle size and phase and therefore influences many characteristics of aerosols relevant to air quality and climate. However, the water uptake properties of many important atmospheric aerosol systems, including those related to the oceans, are still not fully understood. Therefore, the primary aim of this PhD research program was to investigate the water uptake properties of marine aerosols. In particular, the effect of organics on marine aerosol water uptake was investigated. Field campaigns were conducted at remote coastal sites on the east coast of Australia (Agnes Water; March-April 2007) and west coast of Ireland (Mace Head; June 2007), and laboratory measurements were performed on bubble-generated sea spray aerosols. A combined Volatility-Hygroscopicity-Tandem Differential Mobility Analyser (VH-TDMA) was employed in all experiments. This system probes the changes in the hygroscopic properties of nanoparticles as volatile organic components are progressively evaporated. It also allows particle composition to be inferred from combined volatility-hygroscopicity measurements. Frequent new particle formation and growth events were observed during the Agnes Water campaign. The VH-TDMA was used to investigate freshly nucleated particles (17-22.5 nm) and it was found that the condensation of sulphate and/or organic vapours was responsible for driving particle growth during the events. Aitken mode particles (~40 nm) were also measured with the VH-TDMA. In 3 out of 18 VH-TDMA scans evaporation of a volatile, organic component caused a very large increase in hygroscopicity that could only be explained by an increase in the absolute water uptake of the particle residuals, and not merely an increase in their relative hygroscopicity. This indicated the presence of organic components that were suppressing the hygroscopic growth of mixed particles on the timescale of humidification in the VH-TDMA (6.5 secs). It was suggested that the suppression of water uptake was caused by either a reduced rate of hygroscopic growth due to the presence of organic films, or organic-inorganic interactions in solution droplets that had a negative effect on hygroscopicity. Mixed organic-inorganic particles were rarely observed by the VH-TDMA during the summer campaign conducted at Mace Head. The majority of particles below 100 nm in clean, marine air appeared to be sulphates neutralised to varying degrees by ammonia. On one unique day, 26 June 2007, particularly large concentrations of sulphate aerosol were observed and identified as volcanic emissions from Iceland. The degree of neutralisation of the sulphate aerosol by ammonia was calculated by the VH-TDMA and found to compare well with the same quantity measured by an aerosol mass spectrometer. This was an important verification of the VH-TMDA‘s ability to identify ammoniated sulphate aerosols based on the simultaneous measurement of aerosol volatility and hygroscopicity. A series of measurements were also conducted on sea spray aerosols generated from Moreton Bay seawater samples in a laboratory-based bubble chamber. Accumulation mode sea spray particles (38-173 nm) were found to contain only a minor organic fraction (< 10%) that had little effect on particle hygroscopicity. These results are important because previous studies have observed that accumulation mode sea spray particles are predominantly organic (~80% organic mass fraction). The work presented here suggests that this is not always the case, and that there may be currently unknown factors that are controlling the transfer of organics to the aerosol phase during the bubble bursting process. Taken together, the results of this research program have significantly improved our understanding of organic-containing marine aerosols and the way they interact with water vapour in the atmosphere.

APA, Harvard, Vancouver, ISO, and other styles

24

Jaecker-Voirol, Anne. "Etude physico-chimique de la formation des aerosols : application aux pluies acides et a la stratosphere." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13222.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Gramotnev, Galina. "Analysis of dispersion and propagation of fine and ultra fine particle aerosols from a busy road." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16338/1/Galina_Gramotnev_Thesis.pdf.

Full text

Abstract:

Nano-particle aerosols are one of the major types of air pollutants in the urban indoor and outdoor environments. Therefore, determination of mechanisms of formation, dispersion, evolution, and transformation of combustion aerosols near the major source of this type of air pollution - busy roads and road networks - is one of the most essential and urgent goals. This Thesis addresses this particular direction of research by filling in gaps in the existing physical understanding of aerosol behaviour and evolution. The applicability of the Gaussian plume model to combustion aerosols near busy roads is discussed and used for the numerical analysis of aerosol dispersion. New methods of determination of emission factors from the average fleet on a road and from different types of vehicles are developed. Strong and fast evolution processes in combustion aerosols near busy roads are discovered experimentally, interpreted, modelled, and statistically analysed. A new major mechanism of aerosol evolution based on the intensive thermal fragmentation of nano-particles is proposed, discussed and modelled. A comprehensive interpretation of mutual transformations of particle modes, a strong maximum of the total number concentration at an optimal distance from the road, increase of the proportion of small nano-particles far from the road is suggested. Modelling of the new mechanism is developed on the basis of the theory of turbulent diffusion, kinetic equations, and theory of stochastic evaporation/degradation processes. Several new powerful statistical methods of analysis are developed for comprehensive data analysis in the presence of strong turbulent mixing and stochastic fluctuations of environmental factors and parameters. These methods are based upon the moving average approach, multi-variate and canonical correlation analyses. As a result, an important new physical insight into the relationships/interactions between particle modes, atmospheric parameters and traffic conditions is presented. In particular, a new definition of particle modes as groups of particles with similar diameters, characterised by strong mutual correlations, is introduced. Likely sources of different particle modes near a busy road are identified and investigated. Strong anti-correlations between some of the particle modes are discovered and interpreted using the derived fragmentation theorem. The results obtained in this thesis will be important for accurate prediction of aerosol pollution levels in the outdoor and indoor environments, for the reliable determination of human exposure and impact of transport emissions on the environment on local and possibly global scales. This work will also be important for the development of reliable and scientifically-based national and international standards for nano-particle emissions.

APA, Harvard, Vancouver, ISO, and other styles

26

Gramotnev, Galina. "Analysis of dispersion and propagation of fine and ultra fine particle aerosols from a busy road." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16338/.

Full text

Abstract:

Nano-particle aerosols are one of the major types of air pollutants in the urban indoor and outdoor environments. Therefore, determination of mechanisms of formation, dispersion, evolution, and transformation of combustion aerosols near the major source of this type of air pollution - busy roads and road networks - is one of the most essential and urgent goals. This Thesis addresses this particular direction of research by filling in gaps in the existing physical understanding of aerosol behaviour and evolution. The applicability of the Gaussian plume model to combustion aerosols near busy roads is discussed and used for the numerical analysis of aerosol dispersion. New methods of determination of emission factors from the average fleet on a road and from different types of vehicles are developed. Strong and fast evolution processes in combustion aerosols near busy roads are discovered experimentally, interpreted, modelled, and statistically analysed. A new major mechanism of aerosol evolution based on the intensive thermal fragmentation of nano-particles is proposed, discussed and modelled. A comprehensive interpretation of mutual transformations of particle modes, a strong maximum of the total number concentration at an optimal distance from the road, increase of the proportion of small nano-particles far from the road is suggested. Modelling of the new mechanism is developed on the basis of the theory of turbulent diffusion, kinetic equations, and theory of stochastic evaporation/degradation processes. Several new powerful statistical methods of analysis are developed for comprehensive data analysis in the presence of strong turbulent mixing and stochastic fluctuations of environmental factors and parameters. These methods are based upon the moving average approach, multi-variate and canonical correlation analyses. As a result, an important new physical insight into the relationships/interactions between particle modes, atmospheric parameters and traffic conditions is presented. In particular, a new definition of particle modes as groups of particles with similar diameters, characterised by strong mutual correlations, is introduced. Likely sources of different particle modes near a busy road are identified and investigated. Strong anti-correlations between some of the particle modes are discovered and interpreted using the derived fragmentation theorem. The results obtained in this thesis will be important for accurate prediction of aerosol pollution levels in the outdoor and indoor environments, for the reliable determination of human exposure and impact of transport emissions on the environment on local and possibly global scales. This work will also be important for the development of reliable and scientifically-based national and international standards for nano-particle emissions.

APA, Harvard, Vancouver, ISO, and other styles

27

Carter-Fenk, Kimberly Anne. "Structure, Adsorption Mechanisms, and Vibrational Exciton Formation at Proxy Marine Interfaces." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1617809603306859.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Jouan, Caroline. "Les nuages de glace en arctique : mécanismes de formation." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-00843520.

Full text

Abstract:

Les mécanismes de formation des nuages de glace arctiques durant la nuit polaire sont encore mal définis en raison de l'absence d'observations et de l'éloignement de cette région. Pourtant, leur influence sur les conditions météorologiques et sur le climat dans l'hémisphère nord est d'une importance primordiale ; et les connaissances sur la modification de leurs propriétés, liées à des processus d'interaction aérosol-nuage, doivent être améliorées. Les fortes concentrations d'aérosols en Arctique durant la nuit polaire sont associées au transport des aérosols anthropiques des latitudes moyennes jusqu'au pôle Nord. Les observations et les modèles montrent que cela peut conduire à un transport important de particules d'aérosol acidifiées. Les mesures en laboratoire et in situ montrent qu'à basse température (< -30°C), le revêtement d'acide sur les noyaux glaçogènes (IN) peut réduire leurs propriétés de nucléation de la glace. Par conséquent, leur concentration est réduite dans ces régions entraînant une plus faible concentration de plus gros cristaux de glace en raison d'une diminution de la compétition pour une humidité disponible similaire. De nombreuses mesures de terrain et par télédétection par satellite (CloudSat et CALIPSO) révèlent l'existence de deux types de nuages de glace (TIC) en Arctique durant la nuit polaire. Les nuages de glace de type 1 (TIC-1) ne sont visibles que par le lidar tandis que les nuages de glace de type 2 (TIC-2) sont perçus à la fois par le lidar et le radar. Les TIC-2 sont divisés en TIC-2A et TIC-2B. Les TIC-2A sont recouverts d'une fine couche de petits cristaux de glace non-précipitant (invisible par le radar) (TIC-1), tandis que les TIC-2B ne le sont pas. Ils sont caractérisés par une faible concentration de gros cristaux de glace. On suppose que la microstructure des TIC-2B est liée à l'acidification des aérosols. Pour vérifier cette hypothèse, des études de cas et des approches statistiques ont été combinées afin d'analyser le transport des aérosols et les propriétés des nuages de glace en Arctique. La première partie de la thèse enquête sur les propriétés microphysiques des TIC-1/2A et TIC-2B, en analysant des mesures aéroportées et satellitaires de cas spécifiques observés durant la campagne de mesures ISDAC (Alaska, Avril 2008). Pour la première fois, les microstructures des TIC-1/2A et TIC-2B en Arctique sont comparées en utilisant les observations in-situ des nuages. (...) La deuxième partie de la thèse enquête sur l'origine des masses d'air formant deux cas spécifiques de TICs ISDAC : TIC-1/2A (1 Avril 2008) et TIC-2B (15 Avril 2008), en utilisant des outils de trajectoire et des données satellitaires.

APA, Harvard, Vancouver, ISO, and other styles

29

Pettibone, Alicia Stanier Charles O. "Toward a better understanding of new particle formation." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/420.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Lamkaddam, Houssni. "Etude en atmosphère simulée de la formation d'Aérosol Organique Secondaire issue de la photooxydation du n-dodécane : impact des paramètres environnementaux." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1128/document.

Full text

Abstract:

L’aérosol organique secondaire (AOS), fraction majoritaire de l’aérosol submicronique, joue un rôle important sur la santé, l’environnement et le climat. L’évaluation de son impact constitue un véritable enjeu pour la communauté scientifique. Toutefois, nos connaissances actuelles sur les processus de formation d’AOS et sa composition chimique sont encore très lacunaires, et en l’occurrence, limitent le développement des modèles atmosphériques permettant de quantifier les impacts des AOS sur la qualité de l’air et le système climatique. Ainsi, l’objectif de ce travail est de produire un ensemble de données expérimentales fournissant des points de contrainte afin d’évaluer et d’améliorer les modèles. Pour ce faire, la formation d’AOS a été étudiée à partir de la photooxydation d’un précurseur modèle, le n-dodécane, dans la chambre de simulation atmosphérique CESAM. La composition chimique a été élucidée par des techniques spectrométriques et chromatographiques permettant d’identifier les différentes espèces constituant la phase gazeuse et particulaire. En particulier, de nouveaux mécanismes en phase condensée ont été proposés afin d’expliquer la formation des acides carboxyliques et des lactones, identifiés pour la première fois dans l’AOS d’un alcane. Ces derniers pourront être implémentés dans les modèles. Une grande diversité de conditions environnementales, telles que la température, l’humidité relative et la présence/absence de particules préexistantes, a été prise en compte dans ces travaux. Notamment, l’étude de l’influence de la température a mis en évidence une faible sensibilité de ce paramètre sur les rendements de production d’AOS. Tandis que l’étude sur l’effet de l’humidité relative, elle, a montré que l’ajout d’eau dans le système réactionnel au-delà de 5% abaisse les rendements d’AOS de près d’un facteur 2 en comparaison à des conditions sèches. Ainsi, la formation potentielle d’AOS sous ces différentes conditions a permis d’aboutir à des paramétrisations directement utilisables par les modélisateurs. Une caractérisation des effets de paroi dans CESAM, i.e. les pertes en phase gazeuse et particulaire, a également été menée
Secondary Organic Aerosol (SOA), the major fraction of the submicron aerosol, plays a key role on health, environment and climate. The evaluation of its impacts is a real challenge for the scientific community. Our current knowledge of SOA formation processes and chemical composition is still very deficient and limit the development of atmospheric models to quantify the impacts of SOA on air quality and climate system. Therefore, the aim of this work is to produce a set of experimental data to use to constrain and improve the models. To do that, the SOA formation has been studied from the photooxidation of a model precursor, n-dodecane, in the CESAM environmental chamber. The chemical composition has been investigated by spectrometric and chromatographic techniques which allowed us to identify the reaction products constituting the gaseous and particulate phases. In particular, new condensed phase mechanisms have been proposed to explain the formation of carboxylic acids and lactones, identified for the first time. These could be implemented in the models. A wide variety of environmental conditions, such as temperature, relative humidity and the presence/absence of preexisting particles, have been taken into account in this work. The study of the temperature influence has shown a low sensitivity of this parameter on the SOA production. While the study relative humidity effect has shown that adding water to the reaction system beyond 5% lowers SOA yields by almost a factor of 2 in comparison to dry conditions. The SOA formation potential, under these conditions, has been evaluated, and resulted in parameterizations which could be useful for modelers. Furthermore, a characterization of the wall effects in CESAM, i.e. gas and particulate phase wall losses, has been carried out

APA, Harvard, Vancouver, ISO, and other styles

31

Lannuque, Victor. "Formation de l’aérosol organique secondaire dans les modèles de qualité de l’air : développement d’une paramétrisation sur la base de simulations explicites." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1129.

Full text

Abstract:

L’oxydation gazeuse des composés organiques émis dans l’atmosphère mène à la formation de milliers de composés organiques secondaires (COS). Une fraction de ces COS est peu volatile, et peut se partager entre la phase gazeuse et la phase particulaire formant ainsi des aérosols organiques secondaires (AOS). Les AOS contribuent majoritairement à la composition des particules, participant entre 20 et 80 % à la masse totale des aérosols fins et influencent ainsi leurs impacts sur l’environnement, en particulier sur la qualité de l’air et le climat. Ces impacts sont quantifiés à l’aide de modèles de chimie-transport (CTM). Les comparaisons avec les mesures in situ montrent que les variations spatiales et temporelles de la masse d’AOS ne sont pas correctement simulées par les CTM. Dans ces modèles, la formation d’AOS est représentée de façon simplifiée à l'aide de paramétrisations empiriques développées sur la base d'observations en chambres de simulation atmosphérique. Il est donc primordial de repenser et d’améliorer la représentation des aérosols organiques dans les CTM pour diagnostiquer l’origine de la pollution atmosphérique par les particules fines, améliorer la fiabilité de la prévision des épisodes de pollution et évaluer l'impact des aérosols sur l'environnement. Les objectifs de cette thèse sont de :• explorer l’influence des conditions environnementales sur la formation et les propriétés des AOS,• développer une nouvelle paramétrisation de formation de l’AOS sur la base d’une représentation déterministe de la chimie atmosphérique,• évaluer cette paramétrisation en CTM par comparaison avec des mesures in-situ.Les modèles déterministes permettent de représenter la non-linéarité des processus de formation de l'AOS. Le modèle déterministe GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) est un outil de modélisation numérique qui intègre les données élémentaires (cinétiques et thermodynamiques) issues des études en laboratoire. Dans le cadre de cette thèse, des scénarios d’oxydation en conditions environnementales ont été développés et GECKO-A a été utilisé pour étudier l’impact des facteurs environnementaux (température, teneur en NOx, ensoleillement...) sur la formation et les propriétés des AOS. Sur la base de ces simulations, une nouvelle paramétrisation pour la formation d’AOS a été développée: VBS-GECKO. L’évaluation de la VBS-GECKO en modèle de boîte a montré une bonne reproduction des concentrations en aérosols organiques (AO) avec une RMSE inférieure à 20%. La VBS-GECKO a été intégrée au CTM CHIMERE pour simuler les concentrations estivales d’AO au dessus de l’Europe. Son utilisation conduit à une sensible amélioration de la masse d’AO simulée par rapport à la paramétrisation de référence utilisée dans CHIMERE. La VBS-GECKO a également été utilisé pour étudier (i) les sources et propriétés des AOS et (ii) différentes représentation des émissions de composés organiques semi-volatils et de volatilité intermédiaire par le trafic routier
The gaseous oxidation of organic compounds emitted into the atmosphere leads to the formation of thousands of secondary organic compounds (SOC). A fraction of these SOC is low volatile, and can partition between the gaseous phase and the particulate phase, forming secondary organic aerosols (SOA). The SOA are a main component of the particles, representing between 20% and 80% of the total mass of fine aerosols. Therefore, SOA contribute to the impact of aerosols on the environment, in particular air quality and climate. The quantification of the SOA impacts is estimated using chemical-transport models (CTM). Comparisons with in situ measurements show that the spatial and temporal variations of SOA mass are not correctly simulated by CTM. In these models, the SOA formation is represented in a simplified way, using empirical parameterizations developed on the basis of observations performed in atmospheric simulation chambers. Improving the representation of organic aerosols in CTM is therefore required to diagnose the origin of air pollution by fine particles, improve the reliability of pollution episode prediction and assess the impact of aerosols on the environment. The objectives of this thesis are :• to explore the influence of environmental conditions on SOA formation and properties,• to develop a new parameterization of SOA formation based on a deterministic representation of atmospheric chemistry,• to evaluate this parameterization in CTM by comparison with in-situ measurements. Deterministic models represent the non-linearity of SOA formation processes. The model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is a numerical modelling tool that integrates the elementary data (kinetics and thermodynamics) from laboratory studies. In this thesis, oxidation scenarios representative of various environmental conditions were developed and GECKO-A was used to study the impact of environmental factors (temperature, NOx concentrations, solar radiations, etc.) on the formation and the properties of the SOA. On the basis of these simulations, a new parameterization for SOA formation was developed: VBS-GECKO. The evaluation of the VBS-GECKO in box model has shown a good reproduction of the organic aerosol (OA) concentrations with RMSE lesser than 20%.The VBS-GECKO was integrated into the CHIMERE CTM to simulate summer concentrations of OA over Europe. Simulated OA are significantly improved compared to the reference parameterization used in CHIMERE. The VBS-GECKO was also used to study (i) the sources and properties of SOA and (ii) different representations of emissions of semi-volatile and intermediate volatility organic compounds by road traffic

APA, Harvard, Vancouver, ISO, and other styles

32

Huang, Xiaofeng. "Formation mechanisms of water-soluble organic compounds in atmospheric aerosols /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202005%20HUANG.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Gérard, Violaine. "Surfactants in atmospheric aerosols and their role on cloud formation." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1216/document.

Full text

Abstract:

Les nuages sont essentiels dans le cycle de l'eau et dans le budget climatique mais certains aspects de leur formation sont encore incompris. La théorie de Köhler prédit que les surfactants devraient favoriser l'activation des particules en goutte de nuage alors que les modèles actuels les considèrent comme négligeables. Au début de ce travail de thèse, quelques études commençaient à démontrer le contraire mais des preuves du rôle de ces composés dans l'atmosphère étaient encore manquantes, d'où l'objectif de ce travail de thèse. Le développement d'une méthode pour déterminer la concentration en surfactants dans les aérosols a conduit aux premières courbes de tension de surface de surfactants atmosphériques dans des aérosols PM2.5 côtiers (Suède), et à l'identification du ratio C/CMC comme paramètre clé contrôlant l'efficacité des aérosols à former des nuages. Une seconde étude a révélé des corrélations fortes entre la présence de nuages et les propriétés intrinsèques des surfactants dans des aérosols PM1 boréaux (Finlande), démontrant pour la première fois le rôle des surfactants dans la formation des gouttes de nuage à partir d'observations directes dans l'atmosphère. Les résultats prédisent un nombre de noyaux de condensation en moyenne quatre fois plus important que lorsque les effets des surfactants étaient négligés, montrant l‘importance d'inclure l'effet des surfactants dans les modèles prédictifs. Cette importance a été confirmée en laboratoire par des expériences sur des gouttes individuelles microniques par l'augmentation de leur taille en présence de surfactants. Enfin, les observations à partir des différentes études indiquent une origine biologique des surfactants dans les aérosols atmosphériques
Clouds are essential components of the Earth’s hydrological system and climate but some aspects of their formation are still not completely understood. In particular, although Köhler theory predicts that surfactants should enhance cloud droplet activation, current models consider this role negligible. At the time of this PhD work, a few studies had started to demonstrate the contrary but atmospheric evidence for the role of these compounds was still missing and very little was known about their atmospheric concentrations, sources, and mechanism of action. The objective of this PhD work was to investigate these aspects. A method was developed to quantify surfactant concentrations in aerosols. Its application led to the first absolute atmospheric surfactants’ surface tension curves, in coastal PM2.5 aerosols in Sweden, and to the identification of the ratio C/CMC as the key parameter controlling the cloud-forming efficiency of aerosols. A second study revealed strong correlations between cloud occurrence and intrinsic surfactant properties in boreal PM1 aerosols in Finland, demonstrating for the first time the role of surfactants in cloud formation from direct atmospheric observations. The results predicted Cloud Condensation Nuclei numbers four times larger on average than when neglecting surfactant effects, showing the importance of including surfactant effects in cloud predictions models. The role of surfactants inferred from macroscopic measurements was confirmed by laboratory experiments on individual micron-sized droplets showing an increase of droplet growth in the presence of surfactants. Finally, observations from the different field studies indicated a biological origin for the surfactants present in atmospheric aerosols

APA, Harvard, Vancouver, ISO, and other styles

34

Zuberi, Bilal 1976. "Microphysics of atmospheric aerosols : phase transitions and cloud formation mechanisms." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17654.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2003.
Vita.
Includes bibliographical references (leaves 134-148).
Clouds play an extremely important role in our atmosphere, from controlling the local weather, air pollution and chemical balance in the atmosphere to affecting long-term climatic changes at local, regional and global scales. The mechanisms through which tropospheric clouds form are still not fully understood, leading to gross uncertainties in understanding the effect of atmospheric aerosols on the environment. Using laboratory measurements, microphysical properties of typical micro-meter size atmospheric aerosols are investigated in this study. Upper tropospheric ice clouds (cirrus) form when ice is nucleated either homogeneously or heterogeneously in aqueous aerosols. We have investigated the homogeneous and heterogeneous ice nucleation in aqueous particles. Our results for homogeneous nucleation in aqueous ammonium nitrate particles show that the current thermodynamic models do not correctly predict water activities in these particles under super-saturated conditions. High super-saturations are required for ice to nucleate homogeneously in aqueous ammonium nitrate particles. We have also investigated the role of crystallized salt cores, such as solid ammonium sulfate and letovicite, in the heterogeneous nucleation of ice in saturated aqueous ammonium sulfate particles. Our results show that the surface morphology and defects on microcrystals could result in the creation of active sites, leaving the crystallized salt cores as potent ice nuclei under certain conditions. We have also investigated the role of mineral dust and soot, major components of insoluble particulates in the atmosphere, as ice-nuclei. We have found mineral dust to be an effective ice nuclei but both fresh and aged soot do not promote ice nucleation in aqueous particles.
(cont.) Soot is the most ubiquitous aerosol in the atmosphere. The lifetime and microphysics of nano-porous soot has a large impact on earth's radiative budget, heterogeneous chemistry, urban and regional air pollution and human health. We have investigated the hydrophilic properties of both fresh and aged soot as a function of relative humidity. Our results show that fresh hydrophobic soot oxidized (aged) by OH/0₃/UV in the presence of water vapor or by exposure to concentrated HNO₃ becomes hydrophilic and exhibits a greater affinity for water. Due to this increased hydrophilicity, aged soot can be easily entrained inside existing liquid cloud droplets, and even activate as cloud condensation nuclei at high super-saturations, thus influencing its heterogeneous chemistry, radiative properties and atmospheric lifetime.
by Bilal Zuberi.
Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

35

Liu, Jiumeng. "Chemical and optical properties of organic aerosols in the atmosphere over continental US: formation, partitioning, and light absorption." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50370.

Full text

Abstract:

The chemical and optical properties of particulate organic compounds remain unclear, which leaves large uncertainties in the estimation of global radiative transfer balance. Gas and find particle (PM2.5) phase formic acid concentrations were measured with online instrumentation during separate one-month studies in the summer of 2010 in Los Angeles (LA), CA, and Atlanta, GA, and the gas-particle partitioning behavior was investigated and compared with that of water-soluble organic compounds (WSOC). The diurnal profiles clearly indicated that the photochemistry production serves as a strong source for the formation of organics, while the correlation between the gas and particle phase suggested that another partitioning route, the aqueous reactions, is also very important. Later, the optical properties of light-absorbing organic compounds were examined. Little is known about the optical importance of light absorbing particulate organic compounds (brown carbon), especially its extent and absorption relative to black carbon throughout the tropospheric column. Mie theory was applied to size-resolved spectrophotometric absorption measurements of methanol and water-extracts from cascade impactor substrates collected at three surface sites around Atlanta, GA, including both urban and rural. These results were applied to similar measurements of brown carbon in extracts from aircraft bulk filter samples collected over central USA. At the surface sites predicted light absorption by brown carbon relative to total absorption (brown carbon plus pure black carbon) was about 10% and 30% at 350 nm, versus 1 and 11% at 450 nm, for water and methanol extracts, respectively. The relative contribution of brown carbon was greater in the free troposphere and significantly increased with altitude. Although this approach has limitations, it demonstrates the ubiquity and significant potential contribution of brown carbon.

APA, Harvard, Vancouver, ISO, and other styles

36

Garbarienė, Inga. "Origin, chemical composition and formation of submicron aerosol particles in the atmosphere." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140520_134625-72680.

Full text

Abstract:

The objective of the work was to investigate physical and chemical properties and sources of the atmospheric aerosol particles in the submicron fraction by combining different analytical techniques. The dependence of concentrations of organic and elemental carbon in different air masses was determined and the contribution of regional and local sources to the net aerosol particle pollution was estimated. Analysis of the size distribution of carbonaceous aerosol particles in background and urban areas was performed. Biogenic organic aerosol made up 15 % of the organic aerosol mass at the Preila atmospheric pollution research station, but in the North Atlantic air masses this factor was up to 50 %. Aerosol and stable isotope ratio mass spectrometry has revealed that traffic is the primary source of aerosol particles in the city, while biomass burning is the primary source at the Rūgšteliškis background station. It was determined that secondary anthropogenic organic compounds were dominating (76 %) in Vilnius, while in Rūgšteliškis secondary biogenic organic compounds made up 50 % of the total organic aerosol mass. The influence of the long-range air mass transport on the local origin aerosol particle formation and transformation has been evaluated and it has been shown that volcanic aerosol particles can significantly change the concentration, chemical composition and size distribution of local aerosol particles in the submicron range.
Disertacija skirta smulkiosios aerozolio dalelių frakcijos šaltinių, fizikinių ir cheminių savybių įvertinimui kompleksiškai apjungiant įvairius tyrimo metodus. Darbe susieti elementinės ir organinės anglies koncentracijų pokyčiai su tolimąja oro masių pernaša, įvertinta regiono bei vietinių šaltinių įtaka bendrai aerozolio dalelių taršai. Aprašyti anglies turinčių aerozolio dalelių pasiskirstymai pagal dydį foninėse vietovėse ir miesto aplinkoje. Naudojant aerozolio masių spektrometrą Preilos atmosferos užterštumo tyrimų stotyje buvo identifikuotas biogeninis organinių medžiagų šaltinis, kuris vidutiniškai sudaro 15 % nuo organinių medžiagų masės, tačiau Šiaurės Atlanto oro masėje biogeninių medžiagų indėlis siekia net 50 %. Atlikus kompleksinę aerozolio ir stabiliųjų anglies izotopų masių spektrometrinę analizę buvo nustatyta, kad pirminis anglies turinčio aerozolio dalelių šaltinis mieste yra autotransportas, o Rūgšteliškio foninėje vietovėje – biomasės deginimas. Taip pat buvo nustatyta, kad Vilniuje dominavo antropogeninės antrinės organinės medžiagos (76 %), o Rūgšteliškyje vyravo biogeninės antrinės organinės medžiagos (apie 50%). Vertinant tolimosios oro masių pernašos įtaką vietinės kilmės aerozolio dalelių formavimuisi ir kaitai, buvo nustatyta, kad vulkaninės kilmės aerozolio dalelės turi įtakos submikroninės aerozolio dalelių frakcijos koncentracijai, cheminei sudėčiai ir pasiskirstymui pagal dydį.

APA, Harvard, Vancouver, ISO, and other styles

37

Saunders, Russell W. "Laboratory studies of aerosol formation in the Earth's lower and upper atmosphere." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433795.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Targino, Admir Créso. "Regional studies of the optical, chemical and microphysical properties of atmospheric aerosols : Radiative impacts and cloud formation." Doctoral thesis, Stockholm University, Department of Meteorology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-740.

Full text

Abstract:

Atmospheric particles are ubiquitous in the Earth’s atmosphere and have potential to influence atmospheric chemistry, visibility, global climate and human health, particularly downwind from major pollution sources. The main objective of this thesis was to investigate questions pertaining to the microphysical, chemical and optical properties of aerosol particles by using in situ data collected during four experiments carried out in different regions of the Northern Hemisphere.

The first two papers of this thesis reports on airborne measurements of the aerosol optical properties performed over the North Atlantic and the Los Angeles basin. Airmasses from Europe and North Africa are usually advected in over the North Atlantic, alternating with the background marine conditions. The results showed that the aerosols are not uniformly distributed in the area and variability in the aerosol fields occurs at sub-synoptic scales. It was also observed that the single scattering coefficient varied as the polluted plumes aged, suggesting a relationship between this quantity and transport time. The measurements performed around the Los Angeles basin showed that the area’s complex topography and local meteorological circulations exert a strong control on the distribution of the aerosol in the basin. Large spatio-temporal gradients in the aerosol optical properties were observed along a transect flown from the shore towards the mountains. Profiles flown over sites located on the mountains displayed a stratified configuration with elevated aerosol layers.

Airborne data of residual particles collected in orographic wave clouds over Scandinavia were analyzed using a single particle analysis technique. Mineral dust, organic aerosols and sea salt were the main group of particles identified. Residuals composed predominantly of mineral dust were found in glaciated clouds while organic residuals were found in liquid clouds. The results suggest that organic material may inhibit freezing and have considerable influence on supercooled clouds that form through heterogeneous pathways.

The partitioning of the aerosol particles between cloud droplets and interstitial air has been addressed in terms of their microphysical properties using data obtained at a mountain-top site in Sweden during a stratocumulus event. The results showed that the scavenging efficiency varied during the cloud event, and Aitken-mode particles were also efficiently scavenged in addition to accumulation-mode particles. It is hypothesized that alterations of the aerosol chemical composition occurred during the measurement period, modifying the hygroscopic nature of the particles and decreasing their activation diameter.

APA, Harvard, Vancouver, ISO, and other styles

39

Alvarado, Matthew James. "Formation of ozone and growth of aerosols in young smoke plumes from biomass burning." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45606.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 272-291).
The combustion of biomass is a major source of atmospheric trace gases and aerosols. Regional and global-scale models of atmospheric chemistry and climate take estimates for these emissions and arbitrarily "mix" them into grid boxes with horizontal scales of 10-200 km. This procedure ignores the complex non-linear chemical and physical transformations that take place in the highly concentrated environment of the young smoke plumes. In addition, the observations of the smoke plume from the Timbavati savannah fire [Hobbs et al., 2003] show much higher concentrations of ozone and secondary aerosol matter (nitrate, sulfate, and organic carbon [OC]) in the smoke plume than are predicted by current atmospheric chemistry models. To address these issues, we developed a new model of the gas- and aerosol-phase chemistry of biomass burning smoke plumes called ASP (Aerosol Simulation Program). Here we use ASP to simulate the gas-phase chemistry and particle dynamics of young biomass burning smoke plumes and to estimate the errors introduced by the artificial mixing of biomass burning emissions into large-scale grid boxes. This work is the first known attempt to simultaneously simulate the dynamics, gas-phase chemistry, aerosol-phase chemistry, and radiative transfer in a young biomass burning smoke plume. We simulated smoke plumes from three fires using ASP combined with a Lagrangian parcel model. We found that our model explained the formation of ozone in the Otavi and Alaska plumes fairly well but that our initial model simulation of the Timbavati smoke plume underestimated the formation of ozone and secondary aerosol matter. The initial model simulation for Timbavati appears to be missing a source of OH. Heterogeneous reactions of NO2 and SO2 could explain the high concentrations of OH and the rapid formation of ozone, nitrate and sulfate in the smoke plume if the uptake coefficients on smoke aerosols are large [O(10-3) and O(10-4), respectively]. Uncharacterized organic species in the smoke plume were likely responsible for the rapid formation of aerosol OC. The changes in the aerosol size distribution in our model simulations were dominated by plume dilution and condensational growth, with coagulation and nucleation having only a minor effect.
(cont.) We used ASP and a 3D Eulerian model to simulate the Timbavati smoke plume. We ran two test cases. In the reference chemistry case, the uncharacterized organic species were assumed to be unreactive and heterogeneous chemistry was not included. In the expanded chemistry case, the uncharacterized organic compounds were included, as were heterogeneous reactions of NO2 and SO2 with uptake coefficients of 10-3 and 2x10-4, respectively. The 3D Eulerian model matched the observed plume injection height, but required a large minimum horizontal diffusion coefficient to match the observed horizontal dispersion of the plume. Smoke aerosols reduced the modeled photolysis rates within and beneath the plume by 10%-20%. The expanded chemistry case provided a better match with observations of ozone, OH, and secondary aerosol matter than the reference chemistry case, but still underestimated the observed concentrations. We find that direct measurements of OH in the young smoke plumes would be the best way to determine if heterogeneous production of HONO from NO2 is taking place, and that these measurements should be a priority for future field campaigns. Using ASP within an Eulerian box model to evaluate the errors that can be caused by the automatic dilution of biomass burning emissions into global model grid boxes, we found that even if the chemical models for smoke plume chemistry are improved, the automatic dilution of smoke plume emissions in global models could result in large errors in predicted concentrations of O3, NOx and aerosol species downwind of biomass burning sources. The thesis discusses several potential approaches that could reduce these errors, such as the use of higher resolution grids over regions of intense biomass burning, the use of a plume-in-grid model, or the use of a computationally- efficient parameterization of a 3D Eulerian plume chemistry model.
by Matthew James Alvarado.
Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

40

Pistikopoulos, Panayotis. "Comportement physiochimique des hydrocarbures aromatiques polycycliques, particulaires et gazeux, dans l'atmosphere : mode de formation des aerosols, transport a meso-echelle, adaptation d'un modele-recepteur a des composes reactifs." Paris 7, 1988. http://www.theses.fr/1988PA077140.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Asa-Awuku, Akua Asabea. "The effect of solute dissolution kinetics on cloud droplet formation." Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-11112005-141441/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Barsanti, Kelley Claire. "A general theoretical method for evaluating the formation of high-molecular weight/low-volatility compounds and their contribution to atmospheric organic particulate matter /." Full text open access at:, 2006. http://content.ohsu.edu/u?/etd,6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

D'Auria, Raffaella. "A study of ionic clusters in the lower atmosphere and their role in aerosol formation." Diss., Restricted to subscribing institutions, 2005. http://proquest.umi.com/pqdweb?did=888854191&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Targino, Admir Creso. "Regional studies of the optical, chemical and microphysical properties of atmospheric aerosols : radiative impacts and cloud formation /." Stockholm : Dept. of meteorology, Stockholm university, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-740.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Pushpawela, Buddhi G. "The formation and characteristics of new particles in the atmosphere." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/122854/2/__qut.edu.au_Documents_StaffHome_StaffGroupH%24_halla_Desktop_Buddhi_Pushpawela_Thesis.pdf.

Full text

Abstract:

Airborne particles play a major role in climate change and human health. Drawing on the results of extensive measurements carried out in the relatively clean environment of Brisbane and the heavily polluted megacity of Beijing, this thesis has significantly furthered our knowledge of the physical mechanisms of new particle formation in the lower atmosphere. Several characteristics of new particle formation events, such as their temporal distribution, the effect of wind speed and the role of atmospheric ions on the particle formation rate, were investigated for the very first time.

APA, Harvard, Vancouver, ISO, and other styles

46

Schulz, Christiane [Verfasser]. "Secondary organic aerosol in the pristine Amazonian atmosphere: chemical properties, formation pathways, and interactions with clouds / Christiane Schulz." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1185711856/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Asa-Awuku, Akua Asabea. "The effect of solute dissolution kinetics on cloud droplet formation." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10456.

Full text

Abstract:

This study focuses on the importance of solute dissolution kinetics for cloud droplet formation. To comprehensively account for the kinetics, a numerical model of the process was developed. Simulations of cloud droplet growth were performed for solute diffusivity, droplet growth rates, dry particle and droplet diameters relevant for ambient conditions. Simulations suggest that high ambient supersaturations and a decrease in solute diffusivity are major contributors to significant decreases in effective solute surface concentrations. The numerical simulations were incorporated into Khler theory to assess the impact of dissolution kinetics on the droplet equilibrium vapor pressure. For CCN composed of partially soluble material, a significant increase was found in the equilibrium supersaturation of CCN.

APA, Harvard, Vancouver, ISO, and other styles

48

Lanzafame, Grazia Maria. "Understanding organic aerosol formation processes in atmosphere using molecular markers : a combined measurements-model approach." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS519.

Full text

Abstract:

L’aérosol organique (AO) constitue une large fraction des particules de l’air ambiant qui ont des impacts majeurs sur la qualité de l’air et le climat. Ses sources et processus de formation, surtout pour l’AO secondaire (AOS), sont encore méconnus induisant sa sous-estimation par les modèles de qualité de l’air. Ce travail a pour objectif d’améliorer la modélisation de l’AO en implémentant des émissions et processus de formation de marqueurs moléculaires organiques dans le modèle de chimie-transport CHIMERE. Il est basé sur la comparaison entre des sorties de modèle et de mesures réalisées en région parisienne (site périurbain du SIRTA, 25 km SO de Paris) en 2015 et sur 10 sites urbains en hiver 2014-2015. 25 marqueurs d’AOS biogénique et anthropique ont été quantifiés en phase particulaire et gazeuse et la formation de 10 a été simulée. L’évolution des concentrations en lévoglucosan (marqueur de la combustion de biomasse) a aussi été modélisée. Les résultats ont montré que les émissions de sources ou précurseurs (manquantes ou sous-estimées), les concentrations en radicaux (NO, HO2 et RO2) et le défaut de voies de formation, sont des paramètres clés pour la simulation des marqueurs d’AOS. Une faible dépendance à la T°C du partage gaz-particule a été observée alors que le partage hydrophile non idéal, souvent négligé, semble essentiel. Le lévoglucosan est bien modélisé, même si des sous-estimations existent dans certaines régions et une importante fraction gazeuse théorétique a été mise en évidence. La comparaison mesures/modèle de marqueurs moléculaires est un outil puissant pour évaluer les émissions, les processus physico-chimiques et à terme, estimer les sources d’AO
Organic aerosols (OA) account for a large fraction of ambient air particulate matter and have strong impacts on air quality and climate. As their sources and atmospheric formation processes, notably for secondary OA (SOA), are still not fully understood, their concentrations are often underestimated by air quality models. This work aimed at improving OA modelling by implementing specific organic molecular marker emissions and formation processes into the chemistry-transport model CHIMERE. It was based on the comparison of model outputs with measurements from field studies performed in the Paris region (suburban site of SIRTA, 25 km SW of Paris) over 2015 and 10 French urban locations in winter 2014-2015. 25 biogenic and anthropogenic SOA markers have been quantified in both, particulate and gas phases and the formation pathways of 10 have been developed and simulated using CHIMERE. The evolution of levoglucosan concentrations (biomass burning marker) has been also modeled. The results obtained showed that sources and precursor emissions (missing or underestimated), radical concentrations (NO, HO2 and RO2) and the lack of formation pathways, are key parameters for the simulation of SOA markers. Gas/particle partitioning seemed poorly linked to the T°C while the inclusion of hydrophilic non-ideal partitioning, usually neglected, seemed essential. Levoglucosan was well simulated, even if some underestimations existed in some regions. A significant theoretical gaseous fraction was also highlighted. The model/measurements comparison of molecular markers is a powerful tool to evaluate precursor emissions, physicochemical processes and in the end, to estimate OA sources

APA, Harvard, Vancouver, ISO, and other styles

49

Niakan, Negar. "Effects of Molecular Structure of the Oxidation Products of Reactive Atmospheric Hydrocarbons on the Formation of Secondary Organic Particulate Matter, Including the Effects of Water." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/617.

Full text

Abstract:

Organic aerosols have significant effects on human health, air quality and climate. Secondary organic aerosols (SOA) are produced by the oxidation of primary-volatile organic compounds (VOC). For example, α-pinene reacts with oxidants such as hydroxyl radical (OH), ozone (O3), and nitrate radical (NO3), accounting for a significant portion of total organic aerosol in the atmosphere. Experimental studies have shown that the oxidation process between α-pinene and ozone has the most significant impact in the formation of SOA (Hoffmann et al., 1997). Most of the models used to predict SOA formation, however, are limited in that they neglect the role of water due to uncertainty about the structure and nature of organic compounds, in addition to uncertainty about the effect of varying relative humidity (RH) on atmospheric organic particulate matter (OPM) (Kanakidou et al., 2005). For this study, structures of organic compounds involved in the formation of SOA are estimated, and the role of water uptake is incorporated in the process. The Combinatorial Aerosol Formation Model (CAFM) is a deterministic model used to determine the amount of organic mass (Mo µg m-3) formation based on the predicted structures. Results show that the amount of SOA that is formed is almost negligible when the amount of parent hydrocarbon involved in the reaction is low (i.e. around 5 µg m-3), especially at lower RH. Observing compounds with a greater number of polar groups (alcohol and carboxylic acid) indicates that structure has a significant effect on organic mass formation. This observation is in agreement with the fact that the more hydrophilic the compound is, the higher RH, leading to more condensation into the PM phase.

APA, Harvard, Vancouver, ISO, and other styles

50

Roveretto, Marie. "Formation et vieillissement des aérosols : impact de la photochimie hétérogène." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1346.

Full text

Abstract:

Les interfaces sont omniprésentes dans l'environnement et, de plus, de nombreux processus atmosphériques clés, comme les dépôts de gaz, la formation d'aérosol et de nuages, sont, à un stade ou à un autre, fortement touchés par les processus physiques et chimiques qui se produisent aux interfaces. Malheureusement, ces réactions hétérogènes ne sont pas entièrement comprises à ce jour et limitent notre capacité à simuler et quantifier l’impact des aérosols du fait de grandes incertitudes quant à leur formation et leur évolution dans la troposphère. Ce travail de thèse se propose donc d’améliorer nos connaissances sur les réactions photochimiques aux interfaces air/liquide afin d’obtenir une compréhension fondamentale des processus sous-jacents, ce qui pourrait être crucial pour l'évaluation de leurs impacts atmosphériques. Premièrement la réactivité de l’acide stéarique à l’interface air/eau sous irradiation a été étudiée dans différentes matrices grâce un outil très sensible, la balance de Langmuir. Nous avons observé la dégradation des monocouches d’acide stéarique sous irradiation et ce, même en l’absence de photosensibilisateur. Les expériences réalisées avec des monocouches dans différents états de surface indiquent que la pression de surface exerce une influence sur cette réactivité. Le couplage APCI-Orbitrap a été utilisé pour détecter et identifier des composés halogénés produits à partir d’une solution irradiée contenant un photosensibilisateur à savoir l’acide 4-benzoylbenzoïque. Les effets de l’octanol comme surfactant et de l’acide citrique comme donneur de protons sur ces réactions photosensibilisées ont également été examinés. De plus, la formation d’aérosols secondaires et leur vieillissement en milieu marin (au Cap-Vert) ont été étudiés sous différents aspects. Les expériences démontrent clairement l’existence de processus photosensibilisés à l’interface air/mer en tant que source d’aérosols secondaires marins. Pour finir, des travaux sur la photochimie de la matière organique issue de phytoplanctons ont permis de récolter des informations sur leur réactivité dans la phase liquide. Globalement, les résultats obtenus durant cette thèse montrent que la photochimie étudiée ici peut avoir une incidence importante sur la microcouche superficielle des océans et, par extension, sur les aérosols marins
Interfaces are ubiquitous in the environment, and in addition many key atmospheric processes, such as gas deposition, aerosol and cloud formation are, at one stage or the other, strongly affected by physical and chemical processes occurring at interfaces. Unfortunately, these heterogeneous reactions are not fully understood to date and limit our ability to simulate and quantify the impact of aerosols due to large uncertainties in their formation and their evolution in the troposphere. This thesis aims to improve our knowledge about photochemical reactions at the air/liquid interfaces, which could be crucial for the assessment of their atmospheric impacts. Firstly, the reactivity of stearic acid at the air/water interface under irradiation was studied in different matrices thanks to a very sensitive tool, the Langmuir trough. We observed that monolayers of stearic acid undergo degradation under irradiation, even in the absence of photosensitizers. Experiments with monolayers in different surface states indicate that surface pressure influences this reactivity. APCI-Orbitrap coupling was used to detect and identify halogenated compounds produced from an irradiated solution containing a photosensitizer, 4-benzoylbenzoic acid. The effects of octanol as a surfactant and citric acid as a proton donor on these photosensitized reactions were also examined. In addition, the formation of secondary aerosols and their aging in the marine environment (at Cape-Verde) were studied in different conditions. The experiments clearly demonstrate the existence of photosensitized processes at the air/sea interface as a source of marine secondary aerosols. Finally, work on the photochemistry of organic matter from phytoplanktons gave information on their reactivity in the liquid phase. Overall, the results obtained during this thesis show that the photochemistry studied here can have a significant impact on the superficial microlayer of the oceans and, by extension, on marine aerosols

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Atmospheric aerosol formation'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles