To see the other types of publications on this topic, follow the link: Aerosoler.
Dissertations / Theses on the topic 'Aerosoler'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Aerosoler.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Schneider, Friedhelm. "Charakterisierung von Aerosolpartikeln aus der Landwirtschaft /." Hohenheim : Universität Hohenheim, Institut für Agrartechnik, Fachgebiet Verfahrenstechnik der Tierhaltungssysteme, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015489138&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Full text
2
Lundgren, Lennart. "Large organic aerosols in a human exposure chamber : applications in occupational dermatology and lung medicine /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-731-6/.
Full text
3
Gullström, Cecilia. "Use of Satellite Data for Prediction of Weather Impact on EO-Systems." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152284.
Full textAbstract:
To predict the performance of an electro-optical sensor system (EO-system) requires taking the weather situation into consideration. The possibility to use weather data from satellites instead of ground – and flight stations has been investigated. Nearly 170 satellites (about 10% of the functional satellites in orbit) were found to have atmosphere and weather monitoring. A method to select satellite data has been created based on three criteria: (1) the satellite should have a least one payload that measure a weather parameter for EO-system, (2) it should be possible to download data, free of charge, from the specified payload and (3) the satellite should cover geographical areas of interest for a potential user. The investigated performance property is the range, which is affected by many weather parameters, and focus has been on aerosols. The mean value for the aerosol extinction coefficient, for day- and nighttime conditions in December 2016, from the satellite CALIPSO’s lidar instrument Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) has been downloaded from www.earthdata.nasa.gov and implemented in a new developed application to predict the range for an EO-system. In the satellite data, from December 2016, it could be seen that the presence of aerosols, on a global scale, appears below 5 km and that the concentration of aerosols for nighttime condition is higher in local areas. For the test wavelength band of 0.9–2.5 µm, the application showed that the aerosol impact reduced the range by nearly 87%, if the EO-system was in a layer with aerosols. The application for the range prediction of EO-systems is on an early stage and need further development, especially its weather and scene parameters, to become a successful tool for a potential user in the future.<br>Att förutsäga prestandan hos ett elektro-optiskt sensorsystem (EO-system) kräver att man tar hänsyn till bland annat förhållandet i atmosfären. Möjligheten att använda väderdata från satelliter istället för mark- och flygstationer har undersökts. Det hittades nästan 170 satelliter (cirka 10% av de fungerande satelliterna i omloppsbana) med inriktning på atmosfär- och väderövervakning. En metod för att välja ut satellitdata har skapats som baseras på tre kriterier: (1) satelliten ska ha minst ett instrument som mäter en väderparameter för EO-system, (2) man ska, från internet, kunna ladda ner mätdata från det specifika instrumentet och (3) satelliten ska passera över ett område som är av intresse för en potentiell användare. Den prestandaegenskap som har undersökts är räckvidden, som påverkas av flera väderparametrar, där fokus har legat på inverkan från aerosoler. Medelvärdet för extinktionskoefficienten av aerosoler, för dag och natt i december 2016, från satelliten CALIPSO’s lidarinstrument Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) laddades ner från www.earthdata.nasa.gov och användes i en nyutvecklad applikation för att förutsäga räckvidden hos ett EO-system. Från satellitens mätningar i december 2016 kunde man se att förekomsten av aerosoler mestadels befann sig, globalt sett, uppdelat i olika lager under 5 km höjd och att koncentrationen av aerosoler är högre på natten i lokala områden. Applikationens beräkningar visade att förekomsten av aerosoler påverkade räckvidden för exempel våglängdsbandet 0.9–2.5 µm med en försämring upp till 87% när EO-systemet befann sig i ett skikt av aerosoler. Applikationen för att förutsäga räckvidden hos EO-system är i dess begynnelse och kräver vidareutveckling av både väder- och scenparametrar för att det ska bli ett framgångsrikt verktyg.
4
Hofman, Birgitta, and Tina Plejert. "Studier av direkt solinstrålning i Sverige 1983-2003 : en statistisk analys." Thesis, Linköping University, Department of Thematic Studies, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2493.
Full textAbstract:
<p>I denna studie görs ett försök att öka förståelsen kring hur den inkommande direkta solinstrålningen blir påverkad av de gaser och partiklar som finns i atmosfären. Studiens syfte är att se om det statistiskt går att detektera någon trend i SMHI s mätningar av direkt solinstrålning vid elva mätstationer i Sverige mellan åren 1983-2003. Här undersöks även om partikelhalten i luften har förändrats samt om en eventuell trend i direkt solinstrålning kan kopplas ihop med förändrade partikelhalter i luften under samma tidsperiod. Solens cykler och ett förändrat ozonskikt kopplas också samman med resultaten. </p><p>Det finns säsongsvariation i datamaterialet av den direkta solinstrålningen och därför appliceras månadssummerade värden i Seasonal Mann Kendall test for trend som är fördelningsoberoende. För att se hur partiklar och direkt solinstrålning samvarierar görs korrelationstestet Kendall’s Tau i SPSS 11,5. Valet av de variabler som undersöks gentemot direkt solinstrålning är baserat på tidigare forskning av vilka ämnen i atmosfären som kan ha en inverkan på den mängd solinstrålning som når jorden. De aerosoler och partiklar som används som jämförelsematerial (årsmedelvärden) är SO2, SO4, Sot, NO2 och PM10. Mätdata av aerosoler och partiklar har hämtats från IVL Svenska Miljöinstitutet AB vilka jämförs med solinstrålningsdata från SMHI. </p><p>Resultatet från trendtestet för direkt solinstrålning visar att det finns en positiv trend vid 9 av 11 undersökta stationer, solinstrålningen har ökat med 0,5 - 1,2 % år-1. Korrelationstesten mellan direkt solinstrålning och de olika undersökta partiklarna visar att då partikelhalten sjunker ökar den direkta solinstrålningen. Av de undersökta variablerna kan ökningen av solinstrålning till största delen förklaras med en minskad mängd sulfat- och sotpartiklar i atmosfären. Kvävedioxid uppges också som en bidragande faktor, dock liten då minskningen av kvävedioxid inte är så stor. Solens cykler och uttunning av ozonskiktet förklarar endast en mycket liten del av den ökade direkta solinstrålningen.</p>
5
Zeng, Qing-Yin. "Development of molecular techniques for fungal diagnostic research." Doctoral thesis, Umeå : Umeå universitet : Arbetslivsinstitutet, 2005. http://kb.se/resolve?urn=urn:nbn:se:umu:diva-656.
Full text
6
Gallavardin, Stéphane. "Analysis concepts of aerosols by on-line aerosol mass spectrometry." [S.l.] : [s.n.], 2006. http://mediatum2.ub.tum.de/doc/603768/document.pdf.
Full text
7
Alfarra, Mohammedrami. "Insights into atmospheric organic aerosols using an aerosol mass spectrometer." Thesis, University of Manchester, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577471.
Full text
8
Wurl, Daniela. "Optimal Estimation Retrieval of Aerosol Microphysical Properties in the Lower Stratosphere from SAGE II Satellite Observations." Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1533.
Full textAbstract:
A new retrieval algorithm has been developed based on the Optimal Estimation (OE) approach, which retrieves lognormal aerosol size distribution parameters from multiwavelength aerosol extinction data, as measured by the Stratospheric Aerosol and Gas Experiment (SAGE) II in the lower stratosphere. Retrieving these aerosol properties becomes increasingly more difficult under aerosol background conditions, when tiny particles (« 0.1 µm) prevail, to which the experiment is nearly or entirely insensitive. A successful retrieval algorithm must then be able (a) to fill the 'blind spot' with suitable information about the practically invisible particles, and (b) to identify 'the best' of many possible solutions. The OE approach differs from other previously used aerosol retrieval techniques by taking a statistical approach to the multiple solution problem, in which the entire range of possible solutions are considered (including the smallest particles) and characterized by probability density functions. The three main parts of this thesis are (1) the development of the new OE retrieval algorithm, (2) the validation of this algorithm on the basis of synthetic extinction data, and (3) application of the new algorithm to SAGE II measurements of stratospheric background aerosol. The validation results indicate that the new method is able to retrieve the particle size of typical background aerosols reasonably well, and that the retrieved uncertainties are a good estimate of the true errors. The derived surface area densities (A), and volume densities (V ) tend to be closer to the correct solutions than the directly retrieved number density (N), median radius (R), and lognormal distribution width (S). Aerosol properties as retrieved from SAGE II measurements (recorded in 1999) are observed to be close to correlative in situ data. In many cases the OE and in situ data agree within the (OE and/or the in situ ) uncertainties. The retrieved error estimates are of the order of 69% (σN), 33% (σR), 14% (σS), 23% (σA), 12% (σV), and 13% (σReff ). The OE number densities are generally larger, and the OE median particle sizes are generally smaller than those N and R retrieved by Bingen et al. (2004a), who suggest that their results underestimate (N) or overestimate (R) correlative in situ data due to the 'small particle problem'. The OE surface area estimates are generally closer to correlative in situ profiles (courtesy of T. Deshler, University of Wyoming), and larger than Principal Component Analysis (PCA) retrieval solutions of A (courtesy of L. W. Thomason, NASA LaRC) that have been observed to underestimate correlative in situ data by 40-50%. These observations suggest that the new OE retrieval algorithm is a successful approach to the aerosol retrieval problem, which is able to add to the current knowledge by improving current estimates of aerosol properties in the lower stratosphere under low aerosol loading conditions.
9
Li, Xihao. "Characterization of Perphenazine and Scopolamine Aerosols Generated Using the Capillary Aerosol Generator." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/901.
Full textAbstract:
The characterization of perphenazine and scopolamine aerosols generated using the capillary aerosol generator (CAG) was reported. Variables including steady state power, the formulation vehicle, the drug concentration and the formulation flow rate were studied for their effects on the chemical stability and particle size of these drug aerosols.Stability-indicating HPLC and LC-MS assays were developed and validated for perphenazine and scopolamine, respectively. The chemical stability of each compound was investigated under a variety of stress conditions and the structure of degradation products was proposed.Perphenazine aerosols were generated from propylene glycol (PG) formulations with concentrations of 9, 48 and 90mM at formulation flow rates of 2.5 and 5.0µL/s at a series of steady state powers. At higher aerosolization powers, the low concentration formulation (9mM) degraded with dehalogenation being the major pathway. The size of perphenazine aerosols was between 0.4 to 0.6µm. Changing the solute concentration produced only small changes (~0.2µm) in perphenazine aerosol particle size. The formulation flow rate did not significantly affect the aerosol size.Scopolamine degraded significantly when aerosolized in PG formulations. It was possible to generate chemically stable scopolamine aerosols from ethanol formulations. Significant amounts of degradation products were formed only at or above 4.6W at 5.0µL/s. Hydrolysis and dehydration appeared to be the major degradation pathways at higher powers and low formulation flow rate. The MMAD of scopolamine aerosols was between 0.5 and 2.0µm from 8, 20 and 40mM formulations at 5.0 and 10.0µL/s. The size of scopolamine aerosols increased as a function of increasing the solute concentration. Increasing the formulation flow rate increased the linear velocity of the spray, thus the Reynolds number was increased and smaller particles were generated.
10
Posselt, Julia Rebekka. "Influence of giant sea salt aerosols on global precipitation and aerosol indirect effect /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17467.
Full text
11
Dreyfus, Matthew A. "Laboratory and field measurements of organic aerosols with the photoionization aerosol mass spectrometer." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 166 p, 2008. http://proquest.umi.com/pqdweb?did=1654492141&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
12
Lízal, František. "Experimentální výzkum transportu a depozice aerosolů v dýchacím traktu člověka." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234006.
Full textAbstract:
Human health is significantly influenced by inhaled aerosols. Insight to the aerosol transport and deposition mechanisms is a prerequisite for both, toxicological protection against harmful particles and efficient application of inhaled therapeutic aerosols. The purpose of this doctoral thesis was to gain new knowledge of this topic on the basis of in vitro measurements. Phase-Doppler Anemometry was chosen for aerosol transport measurement, for it allows simultaneous measurement of particle size and velocity. Results were processed by means of statistical methods and frequency analysis. Deposition of spherical aerosol particles was measured by Positron Emission Tomography, while deposition of fibrous aerosol was measured by Phase-Contrast Microscopy combined with automated image analysis. All experiments were performed on physical models created on the basis of the real lung geometry. New knowledge of flow characteristics, transition from laminar to turbulent flow, effect of breathing pattern or particle size on aerosol transport and deposition in human lungs are outcomes of this work. Significant effect of the oral cavity was ascertained due to comparison of aerosol deposition in realistic and semi-realistic model with cylindrical smooth walls. Acquired data not merely extended our knowledge of aerosol behavior in lungs but it can also be used for validation of numerical simulations.
13
Sodeman, David Alan. "Characterization of ambient, automobile, and diesel aerosols utilizing aerosol time of flight mass spectrometry /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3144344.
Full text
14
Mills, Jessica Breyan. "Evaluation of the DiSCmini personal aerosol monitor for submicrometer sodium chloride and metal aerosols." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/2584.
Full textAbstract:
This work evaluated the robust, lightweight DiSCmini (DM) aerosol monitor for its ability to measure the concentration and mean diameter of submicrometer aerosols. Tests were conducted with monodispersed and polydispersed aerosols composed of two particle types (sodium chloride, NaCl, and spark generated metal particles, which simulate particles found in welding fume) at three different steady-state concentration ranges (Low, <103; Medium, 103-104; and High, >104 particles/cm3). Particle number concentration, lung deposited surface area (LDSA) concentration, and mean size measured with the DM were compared to those measured with reference instruments, a scanning mobility particle sizer (SMPS) and a handheld condensation particle counter (CPC). Particle number concentrations measured with the DM were within 16% of those measured by the CPC for polydispersed aerosols. Poorer agreement was observed for monodispersed aerosols (±35% for most tests and +101% for 300-nm NaCl). LDSA concentrations measured by the DM were 96% to 155% of those estimated with the SMPS. The geometric mean diameters measured with the DM were within 30% of those measured with the SMPS for monodispersed aerosols and within 25% for polydispersed aerosols (except for the case when the aerosol contained a substantial number of particles larger than 300 nm). The accuracy of the DM is reasonable for particles smaller than 300 nm but caution should be exercised when particles larger than 300 nm are present.
15
Kwok, Philip Chi Lip. "Electrostatics of aerosols for inhalation." Faculty of Pharmacy, 2007. http://hdl.handle.net/2123/1934.
Full textAbstract:
PhD<br>Electrostatics of aerosols for inhalation is a relatively new research area. Charge properties of these particles are largely unknown but electrostatic forces have been proposed to potentially influence lung deposition. Investigation on the relationship between formulation and aerosol charging is required to understand the fundamental mechanisms. A modified electrical low pressure impactor was employed to measure the particles generated from metered dose inhalers and dry powder inhalers. This equipment provides detailed size and charge information of the aerosols. The particles were sized by impaction onto thirteen stages. The net charges in twelve of the size fractions were detected and recorded by sensitive electrometers. The drug deposits were quantified by chemical assay. The aerosol charge profiles of commercial metered dose inhalers were product-dependent, which was due to differences in the drug, formulation, and valve stem material. The calculated number of elementary charges per drug particle of size ≤ 6.06 μm ranged from zero to several ten thousands. The high charge levels on particles may have a potential effect on the deposition of the aerosol particles in the lung when inhaled. New plastic spacers marketed for use with metered dose inhalers were found to possess high surface charges on the internal walls, which was successfully removed by detergent-coating. Detergent-coated spacer had higher drug output than the new ones due to the reduced electrostatic particle deposition inside the spacer. Particles delivered from spacers carried lower inherent charges than those directly from metered dose inhalers. Those with higher charges might be susceptible to electrostatic forces inside the spacers and were thus retained. The electrostatic low pressure impactor was further modified to disperse two commercial Tubuhaler® products at 60 L/min. The DPIs showed drug-specific responses to particle charging at different RHs. The difference in hygroscopicity of the drugs may play a major role. A dual mechanistic charging model was proposed to explain the charging behaviours. The charge levels on drug particles delivered from these inhalers were sufficiently high to potentially affect deposition in the airways when inhaled. Drug-free metered dose inhalers containing HFA-134a and 227 produced highly variable charge profiles but on average the puffs were negatively charged, which was thought to be due to the electronegative fluorine atoms in the HFA molecules. The charges of both HFAs shifted towards neutrality or positive polarity with increasing water content. The spiked water might have increased the electrical conductivity and/or decreased the electronegativity of the bulk propellant solution. The number of elementary charges per droplet decreased with decreasing droplet size. This trend was probably due to the redistribution of charges amongst small droplets following electrostatic fission of a bigger droplet when the Raleigh limit was reached.
16
Zuluaga-Arias, Manuel D. "Spatio-temporal variability of aerosols in the tropics relationship with atmospheric and oceanic environments." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41202.
Full textAbstract:
Earth's radiation budget is directly influenced by aerosols through the absorption of solar radiation and subsequent heating of the atmosphere. Aerosols modulate the hydrological cycle indirectly by modifying cloud properties, precipitation and ocean heat storage. In addition, polluting aerosols impose health risks in local, regional and global scales.
In spite of recent advances in the study of aerosols variability, uncertainty in their spatial and temporal distributions still presents a challenge in the understanding of climate variability. For example, aerosol loading varies not only from year to year but also on higher frequency intraseasonal time scales producing strong variability on local and regional scales. An assessment of the impact of aerosol variability requires long period measurements of aerosols at both regional and global scales.
The present dissertation compiles a large database of remotely sensed aerosol loading in order to analyze its spatio-temporal variability, and how this load interacts with different variables that characterize the dynamic and thermodynamic states of the environment. Aerosol Index (AI) and Aerosol Optical Depth (AOD) were used as measures of the atmospheric aerosol load. In addition, atmospheric and oceanic satellite observations, and reanalysis datasets is used in the analysis to investigate aerosol-environment interactions. A diagnostic study is conducted to produce global and regional aerosol satellite climatologies, and to analyze and compare the validity of aerosol retrievals. We find similarities and differences between the aerosol distributions over various regions of the globe when comparing the different satellite retrievals. A nonparametric approach is also used to examine the spatial distribution of the recent trends in aerosol concentration. A significant positive trend was found over the Middle East, Arabian Sea and South Asian regions strongly influenced by increases in dust events.
Spectral and composite analyses of surface temperature, atmospheric wind, geopotential height, outgoing longwave radiation, water vapor and precipitation together with the climatology of aerosols provide insight on how the variables interact. Different modes of variability, especially in intraseasonal time scales appear as strong modulators of the aerosol distribution. In particular, we investigate how two modes of variability related to the westward propagating synoptic African Easterly Waves of the Tropical Atlantic Ocean affect the horizontal and vertical structure of the environment. The statistical significance of these two modes is tested with the use of two different spectral techniques. The pattern of propagation of aerosol load shows good correspondence with the progression of the atmospheric and oceanic synoptic conditions suitable for dust mobilization over the Atlantic Ocean. We present extensions to previous studies related with dust variability over the Atlantic region by evaluating the performance of the long period satellite aerosol retrievals in determining modes of aerosol variability. Results of the covariability between aerosols-environment motivate the use of statistical regression models to test the significance of the forecasting skill of daily AOD time series. The regression models are calibrated using atmospheric variables as predictors from the reanalysis variables. The results show poor forecasting skill with significant error growing after the 3rd day of the prediction. It is hypothesized that the simplicity of linear models results in an inability to provide a useful forecast.
17
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 textAbstract:
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.
18
Hoffmann, Anne. "Comparative aerosol studies based on multi-wavelength Raman LIDAR at Ny-Ålesund, Spitsbergen." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5242/.
Full textAbstract:
The Arctic is a particularly sensitive area with respect to climate change due to the high surface albedo of snow and ice and the extreme radiative conditions. Clouds and aerosols as parts of the Arctic atmosphere play an important role in the radiation budget, which is, as yet, poorly quantified and understood. The LIDAR (Light Detection And Ranging) measurements presented in this PhD thesis contribute with continuous altitude resolved aerosol profiles to the understanding of occurrence and characteristics of aerosol layers above Ny-Ålesund, Spitsbergen. The attention was turned to the analysis of periods with high aerosol load. As the Arctic spring troposphere exhibits maximum aerosol optical depths (AODs) each year, March and April of both the years 2007 and 2009 were analyzed. Furthermore, stratospheric aerosol layers of volcanic origin were analyzed for several months, subsequently to the eruptions of the Kasatochi and Sarychev volcanoes in summer 2008 and 2009, respectively.
The Koldewey Aerosol Raman LIDAR (KARL) is an instrument for the active remote sensing of atmospheric parameters using pulsed laser radiation. It is operated at the AWIPEV research base and was fundamentally upgraded within the framework of this PhD project. It is now equipped with a new telescope mirror and new detection optics, which facilitate atmospheric profiling from 450m above sea level up to the mid-stratosphere. KARL provides highly resolved profiles of the scattering characteristics of aerosol and cloud particles (backscattering, extinction and depolarization) as well as water vapor profiles within the lower troposphere. Combination of KARL data with data from other instruments on site, namely radiosondes, sun photometer, Micro Pulse LIDAR, and tethersonde system,
resulted in a comprehensive data set of scattering phenomena in the Arctic atmosphere.
The two spring periods March and April 2007 and 2009 were at first analyzed based on meteorological parameters, like local temperature and relative humidity profiles as well as large scale pressure patterns and air mass origin regions. Here, it was not possible to find a clear correlation between enhanced AOD and air mass origin. However, in a comparison of two cloud free periods in March 2007 and April 2009, large AOD values in 2009 coincided with air mass transport through the central Arctic. This suggests the occurrence of aerosol transformation processes during the aerosol transport to Ny-Ålesund. Measurements on 4 April 2009 revealed maximum AOD values of up to 0.12 and aerosol size distributions changing with altitude. This and other performed case studies suggest the differentiation between three aerosol event types and their origin: Vertically limited aerosol layers in dry air, highly variable hygroscopic boundary layer aerosols and enhanced aerosol load across wide portions of the troposphere. For the spring period 2007, the available KARL data were statistically analyzed using a characterization scheme, which is based on optical characteristics of the scattering particles. The scheme was validated using several case studies.
Volcanic eruptions in the northern hemisphere in August 2008 and June 2009 arose the opportunity to analyze volcanic aerosol layers within the stratosphere. The rate of stratospheric AOD change was similar within both years with maximum values above 0.1 about three to five weeks after the respective eruption. In both years, the stratospheric AOD persisted at higher rates than usual until the measurements were stopped in late September due to technical reasons. In 2008, up to three aerosol layers were detected, the layer structure in 2009 was characterized by up to six distinct and thin layers which smeared out to one broad layer after about two months. The lowermost aerosol layer was continuously detected at the tropopause altitude. Three case studies were performed, all revealed rather large indices of refraction of m = (1.53–1.55) - 0.02i, suggesting the presence of an absorbing carbonaceous component. The particle radius, derived with inversion calculations, was also similar in both years with values ranging from 0.16 to 0.19 μm. However, in 2009, a second mode in the size distribution was detected at about 0.5 μm.
The long term measurements with the Koldewey Aerosol Raman LIDAR in Ny-Ålesund
provide the opportunity to study Arctic aerosols in the troposphere and the stratosphere not only in case studies but on longer time scales. In this PhD thesis, both, tropospheric aerosols in the Arctic spring and stratospheric aerosols following volcanic eruptions have been described qualitatively and quantitatively. Case studies and comparative studies with data of other instruments on site allowed for the analysis of microphysical aerosol characteristics and their temporal evolution.<br>Die Arktis ist ein bezüglich Klimaveränderungen besonders sensitives Gebiet, d.h. die globale Erwärmung wirkt sich aufgrund der saisonal hochvariablen Strahlungsbedingungen und der Bodenalbedo dort verstärkt aus.Wolken und Aerosole als Bestandteile der arktischen Atmosphäre spielen dabei eine besondere Rolle im Strahlungsgleichgewicht. Die vorliegende Promotionsarbeit leistet mit Hilfe von LIDAR-Messungen (Light Detection and Ranging) einen Beitrag zum Verständnis von Vorkommen und Eigenschaften von Aerosolschichten über Ny-Ålesund, Spitzbergen. Besonderes Augenmerk liegt dabei auf der Analyse von Zeiträumen mit erhöhter Aerosolbelastung. Es wurde zum einen die arktische Troposphäre zweier Frühjahre (März und April der Jahre 2007 und 2009) untersucht, da im Frühjahr die Aerosol-optische Dicke (AOD) in der Arktis Maximalwerte erreicht. Zum anderen wurden stratosphärische Aerosolschichten vulkanischen Ursprungs analysiert, die in den Sommern 2008 und 2009 nach Ausbrüchen der Kasatochi und Sarychev Vulkane jeweils für mehrere Monate in der unteren Stratosphäre messbar waren.
Das an der AWIPEV Forschungsstation betriebene Koldewey Aerosol Raman LIDAR
(KARL), ein Instrument zur optischen Fernerkundung atmosphärischer Parameter mittels gepulster Laserstrahlung, wurde im Rahmen der Promotion grundlegend überarbeitet und mit einem neuen Teleskop sowie neuen Detektoroptiken versehen. Dies ermöglicht die Profilerfassung ab 450m über dem Meeresspiegel bis in die mittlere Stratosphäre. KARL liefert hochaufgelöste Messungen der Streueigenschaften von Aerosol- undWolkenteilchen (Rückstreuung, Extinktion und Depolarisation) sowieWasserdampfprofile in der unteren Troposphäre. Durch die Kombination von KARL Messungen mit Daten anderer Messgeräte an der AWIPEV Forschungsstation wie Radiosonden, Sonnenphotometer, Micro Pulse LIDAR und Fesselsonden wurde ein umfassender Datenbestand von Streuphänomenen in der arktischen Atmosphäre geschaffen.
Die beiden genannten Frühjahreszeiträume März und April 2007 und 2009 wurden zunächst anhand meteorologischer Parameter, wie lokaler Temperatur- und Feuchteprofile sowie großskaliger Druckmuster und Luftmassenquellgebiete analysiert. Dabei konnte kein eindeutiger Zusammenhang zwischen Quellgebieten und erhöhter AOD festgestellt werden. In einem Vergleich zweier wolkenfreier Perioden im März 2007 und April 2009 war jedoch die höhere Aerosolbelastung in 2009 mit dem Transport von Luftmassen durch die innere Arktis verbunden. Aufgrund der begrenzten Lebensdauer von Aerosolen lässt das entweder Aerosol-Entstehungsprozesse in der Zentralarktis oder Transformationsprozesse während des Transportes nach Ny-Ålesund vermuten. Für Messungen am 4. April 2009 mit Maximalwerten der AOD von bis zu 0.12 konnte die Größe der Aerosolteilchen in verschiedenen Höhen mit Hilfe von Inversionsrechnungen abgeschätzt werden. Diese und andere betrachtete Fallstudien legen eine Unterscheidung von Aerosolereignissen in drei Kategorien nahe, die sich in ihrer Entstehung deutlich unterscheiden: Vertikal begrenzte Aeosolschichten in trockener Luft, zeitlich hochvariable feuchte Aerosolschichten in der planetaren Grenzschicht sowie eine erhöhte Aerosolbelastung über große Teile der Troposphäre. Für das sehr klare Frühjahr 2007 wurden die vorhandenen KARL-Daten mit Hilfe eines Klassifikationsschemas, das auf den optischen Eigenschaften der streuenden Teilchen beruht, statistisch ausgewertet. Das verwendete Schema wurde mit Hilfe von verschiedenen Fallstudien validiert und ermöglicht bei Anwendung auf größere Datenbestände eine aussagekräftige Analyse von jährlichen Schwankungen der Aerosol- und Wolkenvorkommen über Ny-Ålesund.
Die Ausbrüche zweier Vulkane in der nördlichen Hemisphäre im August 2008 und im
Juni 2009 erlaubten die Analyse vulkanischer Aerosolschichten in der Stratosphäre. Die zeitliche Entwicklung der stratosphärischen AOD verlief in beiden Jahren ähnlich mit Maximalwerten von über 0.1 etwa drei bis fünfWochen nach dem jeweiligen Ausbruch. In beiden Jahren wurden bis zum technisch bedingten Abbruch der Messungen jeweils Ende September erhöhte stratosphärische AOD Werte gemessen. Die niedrigste Aerosolschicht konnte jeweils direkt an der Tropopause detektiert werden. Im Jahr 2008 wurden bis zu drei Schichten detektiert, die Struktur 2009 war durch bis zu sechs schmale Schichten gekennzeichnet, die nach etwa zwei Monaten zu einer breiten Schicht verschmierten. Drei Fallstudien zu mikrophysikalischen Aerosoleigenschaften wurden durchgeführt. Dabei wurden für beide Jahre sehr große Brechungsindices von m=(1.53–1.55) - 0.02i ermittelt, die auf eine absorbierende Kohlenstoffkomponente der Vulkanaerosole hinweisen. Der errechnete Teilchenradius war ebenfalls in beiden Jahren vergleichbar mit Werten zwischen 0.16 und 0.19 μm. 2009 wurde zusätzlich ein zweites Maximum der Größenverteilung bei ca. 0.5μm gefunden. Die Langzeitmessungen mit dem Koldewey Aerosol Raman LIDAR KARL in Ny-Ålesund schaffen die Möglichkeit, arktische Aerosole in Troposphäre und Stratosphäre nicht nur in Fallstudien, sondern auch über längere Zeiträume hinweg zu analysieren. Im Rahmen dieser Promotionsarbeit konnten sowohl Aerosolvorkommen in der arktischen Troposphäre im Frühjahr als auch eine vulkanisch bedingte erhöhte Aerosolbelastung in der Stratosphäre qualitativ und quantitativ beschrieben werden. Fallstudien und die Kombination mit Daten anderer Messgeräte ermöglichten Analysen mikrophysikalischer Aerosolparameter und deren Entwicklungsprozesse.
19
Engler, Christa. "Meteorologische Einflüsse auf die Konzentrationen feiner und grober atmosphärischer Aerosolpartikel in Deutschland." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-137034.
Full textAbstract:
Atmosphärische Aerosolpartikel können durch ein breites Spektrum an natürlichen oder anthropogenen Emissionen mit unterschiedlich hohen Konzentrationen in die Atmosphäre freigesetzt werden. Sie beeinflussen den Strahlungshaushalt und damit auch das Klima der Erde und können außerdem durch ihre Präsenz in der Atmosphäre Wechselwirkungen mit Mensch und Natur, also dem gesamten Ökosystem haben. Seit dem Jahr 2010 gelten in der EU Grenzwerte für die PM10 Tagesmittelkonzentration, die jedoch bereits wenige Monate nach Beginn der Gültigkeit an vielen Messstationen überschritten wurden. Das Ziel der vorliegenden Arbeit war eine objektive Bewertung der Herkunft und des Zustandes der an einem Messort ankommenden Luftmasse und der damit verbundenen Schadstoffniveaus.
Im ersten Teil der Arbeit wurden PM10 Messdaten aus fünf Jahren in und um Leipzig sowie analog in fünf verschiedenen Regionen deutschlandweit in Bezug auf PM10 Grenzwertüberschreitungen untersucht. Es wurden Rückwärtstrajektorien für eine Clusteranalyse verwendet, mit der spezifische Wetterlagen unterschieden wurden und diesen dann die einzelnen Messtage mit den zugehörigen Schadstoffkonzentrationen zugeordnet wurden. Hierbei wurde deutlich, dass durch entsprechende meteorologische Bedingungen sowohl lokal als auch regional emittierte Schadstoffe in Bodennähe akkumulieren oder aber auch räumlich verteilt werden können.
Außerdem wurde in dieser Arbeit eine Modellvalidierung vorgestellt. Es wurde das Modellsystem COSMO-MUSCAT/ext-M7 verwendet, dessen Ergebnisse mit Beobachtungsdaten verglichen wurden. Als erstes wurde die Beschreibung der meteorologischen Bedingungen, dann die räumliche Verteilung von PM10, die chemische Partikelzusammensetzung sowie physikalische Aerosolparameter wie Partikelanzahl, -volumen und -durchmesser verglichen. Die Ergebnisse deuten darauf hin, dass nach wie vor Probleme bei der Beschreibung der mikrophysikalischen Aerosoleigenschaften bestehen. Die Größenordnungen der verglichenen Parameter können vom Modell abgebildet werden, dennoch müssen Modellergebnisse nach wie vor mit Vorsicht interpretiert werden, insbesondere hinsichtlich von Prozessen, bei denen die Partikelanzahl eine Rolle spielen.
20
Merk, Daniel. "Uncertainties in the Quantification of Aerosol-Cloud Interactions." Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-225523.
Full textAbstract:
Aerosole dienen als Kondensationskerne (CCN) und verändern die Wolkentropfenkonzentration (Nd) und weitere Wolkeneigenschaften. Nd ist daher ein Schlüsselparameter von Aerosol-Wolken-Wechselwirkungen (ACI). ACI sind bezüglich ihrer Klimarelevanz nur unzureichend bestimmt. ACI wurden auf verschiedenen Skalen und mit unterschiedlichen Methoden von unterschiedlichen Perspektiven aus untersucht, was zu einer großen Variabilität von ACI Metriken in der Literatur führt. Für eine genauere Quantifizierung von ACI, wurden in dieser Arbeit damit verbundene, entscheidende Unsicherheiten diskutiert, u.a. das Einmischen trockener Luft, Unsicherheiten von Retrieval-Methoden und die Konsistenz von Schlüsselparametern auf verschiedenen Skalen. Um Nd und weitere Wolkeneigenschaften aus passiven Satellitenbeobachtungen für Flüssigwasserwolken abzuleiten, wird oft das adiabatische Modell herangezogen. Es wurde untersucht, inwiefern dieses Modell reale Bedingungen wiedergibt. Es wurde gezeigt, dass Wolken typischerweise subadiabatisch sind, mit stark reduziertem Flüssigwassergehalt nahe der Wolkenoberkante. Der Einmischprozess variiert zeitlich stark und erschwert die Quantizierung von ACI. Für unterschiedliche Cloudnet-Stationen variieren die Medianwerte des subadiabatischen Faktors von 0.35+/-0.12 bis 0.48+/-0.22. Dieser hängt stark von der geometrischen Wolkendicke ab, wobei dickere Wolken subadiabatischer sind. Die Ableitung von Nd aus bodenbasierten Radar-Radiometer-Beobachtungen ist sehr sensitiv gegenüber a-priori Annahmen. Um zusätzliche Beobachtungen und Unsicherheiten berücksichtigen zu können, wurde ein neuartiges Optimal Estimation (OE) Retrieval entwickelt und mittels synthetischer Wolkenprofile evaluiert. Mittels einer Sensitivitätsstudie konnte die Verbesserung der Retrieval-Genauigkeit für die OE Methode gezeigt werden, wenn die Beobachtungen der optischen Dicke mit berücksichtigt werden. Die Annahme einer typischen Breite der Tropfengrößenverteilung ist dabei eine der größten Unsicherheiten von Nd (Unsicherheit für die OE Methode etwa 150%, für die Radar-Radiometer-Methode etwa 200%). Desweiteren wurden aus unterschiedlichen Perspektiven abgeleitete wolkenmikrophysikalische Größen hinsichtlich ihrer Konsistenz untersucht. Beim Vergleich von Nd und des Effektivradius (re) vom bodengebundenen Retrieval mit in-situ Beobachtungen für einen Falltag wurde eine gute Übereinstimmung gefunden. Beim Vergleich der von SEVIRI und Bodenstationen abgeleiteten Wolkeneigenschaften haben sich mittlere quadratische Abweichungen des Flüssigwasserpfads und der optischen Dicke von jeweils 65 gm2 und 14 ohne signifikanten Bias gezeigt. Damit zeigt sich SEVIRI für großskalige, statistische ACI-Untersuchungen repräsentativ zur Bodenperspektive. Für individuelle Falltage traten jedoch teils größere Unterschiede auf, welche durch Inhomogenitäten und Auflösungseffekte erklärt werden können. Mit SEVIRI Beobachtungen und aus der MACC Reanalyse abgeleiteten CCN Konzentrationen wurde eine Quantifizierung von ACI für das Jahr 2012 durchgeführt. Dabei wurde für Europa ein deutlicher, mikrophysikalischer Effekt gefunden, d.h. eine Abnahme von re und eine Zunahme von Nd mit zunehmender CCN Konzentration. Im Gegensatz dazu wurde für die Wolkenalbedo kein eindeutiger Anstieg mit der CCN-Konzentration gefunden. Verwendet man die Aerosol-optische Dicke (AOD) anstelle der CCN-Konzentration, sind die Werte der ACI Metrik nur halb so groß. Dieses Ergebnis deutet darauf hin, dass die AOD kein optimaler CCN-Proxy ist.
21
Adikesavalu, Ravichandran. "Preliminary modeling of in-duct desulfurization using condensation aerosols." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177616476.
Full text
22
Junior, Theotonio Mendes Pauliquevis. "\"Os efeitos de aerossóis emitidos por queimadas na formação de gotas de nuvens e na composição da precipitação na Amazônia\"." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-27082007-101307/.
Full textAbstract:
Este trabalho teve como objetivo investigar a relação entre produtos de atividades antropogênicas na Amazônia e sua influência no efeito indireto dos aerossóis no clima. Para isso, foi feita uma caracterização físico-química detalhada dos aerossóis naturais e de queimadas na Amazônia e procurou-se compreender como estes diferentes tipos de aerossóis se comportam como Núcleos de Condensação de Nuvens. Foi estudado também a influência dos aerossóis de queimadas na composição química da precipitação e no transporte de nutrientes. Visando atingir estes objetivos, foram feitas medidas em regiões distintas da Amazônia com relação ao impacto por atividades antropogênicas, principalmente queimadas. Foi possível observar em várias circunstâncias uma relação entre a composição do material particulado e da precipitação, o que nos permitiu concluir que as emissões antropogênicas influenciam significativamente a composição da precipitação. Foram identificadas as principais componentes que afetam a composição do material particulado em suspensão na Amazônia, e concluimos que o material particulado originado de emissões biogênicas é predominante em regiões preservadas, com pequena contribuição também de poeira de solo e transporte de aerossóis marinhos. Em regiões sob influência de atividades antropogênicas, observou-se que a composição dos aerossóis e da precipitação é afetada mesmo na estação úmida. No estudo das propriedades físicas e químicas das partículas de aerossol que são relevantes para o seu papel como Núcleos de Condensação de Nuvens, concluiu-se que a distribuição de tamanho é mais importante do que a composição química das partículas, devido ao fato das emissões de novas partículas por queimadas ocorrer predominantemente acima do diâmetro seco de ativação. A composição química só foi importante em valores de supersaturação baixos (< 0.2%), o que significa que esse efeito pode ser importante para nuvens estratiformes, onde o valor máximo de supersaturação é baixo, devido a baixa velocidade de ascensão das parcelas. A exportação de nutrientes devido ao transporte em larga escala de aerossóis de emissões de queimadas se mostrou particularmente crítica com relação às quantidades de fósforo que estão sendo perdidas irreversivelmente pela floresta amazônica, que foi cerca de 7 vezes maior do que a quantidade reposta por deposição úmida. Essa perda de fósforo pode ser crítica para o ecossistema em longo prazo.<br>The main objective of this study was to investigate the relationship between anthropogenic emissions in the Amazon basin and the indirect aerosol effect on climate. A detailed study of physical and chemical properties of natural and biomass burning aerosols was conducted, in order to understand how these completely different aerosols behave as Cloud Condensation Nuclei (CCN). It was also investigated the influence of biomass burning aerosols in chemical composition of precipitation, and transport of nutrients. The measurements were carried out in completely different regions respect to the impact of anthropogenic activities, especially biomass burning emissions. The analysis of aerosols and rainwater chemistry showed that anthropogenic emissions have a significant influence in the composition of precipitation. Factor analysis was applied to perform source identification, and the conclusion is that at remote and free of anthropogenic emission areas, the most important contribution was from biogenic emissions, with a small contribution of soil dust and marine aerosols advection. It was quite different at regions under influence of anthropogenic activities, where measurements showed a clear anthropogenic influence even during wet season both in aerosols and precipitation chemistry. In the study of hygroscopic properties of aerosol particles, the main conclusion was that size distribution of particles is the most important parameter to determine the ability of aerosols to act as CCN, because most of biomass burning emission are particles bigger than the activation diameter. Chemical composition was an important factor only if supersaturation is below 0.2%, because in this supersaturation range the activation diameter is extremely sensible to small changes in supersaturation. Transport of nutrients due to largescale transport of biomass burning aerosols was specially critical concerning phosphorus exportation, estimated as 7 times the apportionment through wet deposition. Continuous exportation of phosphorus can be a long term limitation to the forest ecosystem, if biomass burning activity maintain its present levels.
23
Aiken, Allison Carol. "Quantitative chemical analysis of ambient organic aerosols using high-resolution time-of-flight aerosol mass spectrometry." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337069.
Full text
24
Steele, Henry Donnan 1974. "Investigations of cloud altering effects of atmospheric aerosols using a new mixed Eulerian-Lagrangian aerosol model." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/58445.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004.<br>Includes bibliographical references (p. 275-315).<br>Industry, urban development, and other anthropogenic influences have substantially altered the composition and size-distribution of atmospheric aerosol particles over the last century. This, in turn, has altered cloud albedo, lifetime, and patterns which together are thought to exert a negative radiative forcing on the climate; these are the indirect effects of atmospheric aerosols. The specifics of the process by which aerosol particles seed cloud particles are complex and highly uncertain. The goal of this thesis is to refine understanding of the role of various aerosol types in determining cloud properties. We approach this goal by constructing a new highly detailed aerosol-cloud process model that is designed to simulate condensation upon complex aerosol populations. We use this model to investigate the microphysics of aerosol-cloud interactions, specifically considering the role of cloud dynamics and of the ubiquitous mixed soot / sulfate aerosols. We describe the Mixed Eulerian-Lagrangian Aerosol Model (MELAM). This new computer model of aerosol microphysics is specifically tailored to simulate condensation and activation as accurately as possible. It specifically calculates aerosol thermodynamics, condensation, coagulation, gas and aqueous phase chemistry, and dissolution. The model is able to consider inorganic aerosols and aerosols with both inorganics and insoluble cores; the specific chemical system to be considered is specified by the user in text input files. Aerosol particles may be represented using "sectional distributions" or using a "representative sample" distribution which tracks individual particles.<br>(cont.) We also develop a constant updraft speed, adiabatic parcel model and a variable updraft speed, episodically entraining parcel model to provide boundary conditions to MELAM and allow simulations of aerosol activation in cloud updrafts. Using MELAM and the parcel models, we demonstrate that aerosol activation depends on the composition and size distribution of the sub-cloud aerosol population, on the updraft speed through a parcel's lifting condensation level, on the vertical profile of the updraft speed, and on entrainment. We use a convective parameterization that was developed for use in global or regional models to drive the episodically entraining, variable updraft speed parcel model. Ultimately, reducing the uncertainty of the global impact of the indirect effects of aerosols will depend on successfully linking cloud parameterizations to models of aerosol activation; our work represents a step in that direction. We also consider the activation of mixed soot / sulfate particles in cloud updrafts. We constrain for the first time a model of condensation onto these mixed particles that incorporates the contact angle of the soot / solution interface and the size of the soot core. We find that as soot ages and its contact angle with water decreases, mixed soot / sulfate aerosols activate more readily than the equivalent sulfate aerosols that do not have soot inclusions. We use data from the Aerosol Characterization Experiments (ACE) 1 and 2, and from the Indian Ocean Experiment (INDOEX) to define representative aerosol distributions for clean, polluted, and very polluted marine environments. Using these distributions, we argue that the trace levels of soot observed in clean marine environments do not substantially impact aerosol activation, while the presence of soot significantly increases the number of aerosol that activate in polluted areas.<br>by Henry Donnan Steele.<br>Ph.D.
25
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 textAbstract:
Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.<br>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.
26
Fontal, Maestre Marta. "Estudi exhaustiu de la matèria orgànica submicrònica en aerosols urbans i dels efectes de les transformacions secundàries." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400862.
Full textAbstract:
L’estudi dels compostos orgànics presents a l’atmosfera i el seu origen antropogènic i biogènic, ha estat un tema de gran interès els darrers anys amb l’objectiu de resoldre la problemàtica de la contaminació atmosfèrica de zones urbanes i el seu efecte negatiu sobre la salut de la població, així com per generar estratègies per afavorir la qualitat de l’aire.
Aquest estudi forma part del projecte AERTRANS finançat pel Ministeri de Economia i Competitivitat (Pla Nacional de I+D+i CTQ2009-14777-C02-01) que porta per títol: Estudi comprensiu de la matèria orgànica submicrònica en aerosols urbans i rurals i dels efectes de les transformacions secundàries. En concret, en aquesta tesi s’ha estudiat la composició i les fonts d’emissió de la matèria orgànica dels aerosols atmosfèrics de la denominada fracció ultrafina o PM1 (partícules de diàmetre aerodinàmic inferior a 1 µm) a les ciutats de Madrid i Barcelona, en base als seus nivells de contaminació elevats i localització al sud d’Europa, caracteritzada per nivells d’insolació elevats que afavoreixen les transformacions fotoquímiques dels compostos presents a l’atmosfera. D’altra banda, les condicions meteorològiques són clarament diferents, mentre que Barcelona és una ciutat costanera afectada per un règim de brises i una humitat elevada, Madrid està situat a 667 m sobre el nivell del mar i el seu clima és més sec.
La presa de mostra va incloure períodes setmanals de dues mostres diàries tant a l’hivern com a l’estiu, es van agafar mostres a nivell del carrer i a una alçada aproximada de 50 m sobre el nivell del sòl. Amb aquesta estratègia es van poder investigar les fonts de contaminació, les diferències entre les estacions càlides i les fredes, els processos atmosfèrics relacionats amb el cicle diürn i setmanal, així com els processos relacionats amb la formació dels aerosols secundaris.
S’ha desenvolupat i optimitzat una metodologia analítica i instrumental per a l’anàlisi exhaustiva dels compostos orgànics en mostres de partícules que consisteix bàsicament en una extracció del filtre amb dissolvents orgànics (diclorometà i metanol), seguit de una filtració, separació de l’extracte en fraccions, i concentració d’aquestes per la seva anàlisi per cromatografia de gasos acoblada a espectrometria de masses (GC/MS). Els compostos principals que s’han trobat al material particulat d’ambdues ciutats són els alcans, hidrocarburs aromàtics policíclics (PAH), quinones, anhidrosacàrids, àcids i també productes derivats de l’isoprè i α-pinè. Cal destacar que en el cas dels anhidrosucres relacionats amb la crema de biomassa, levoglucosà, mannosà i galactosà, la metodologia analítica desenvolupada es va validar mitjançant
la participació en un exercici interlaboratori. El seu anàlisi en les mostres de Barcelona va permetre estudiar l’impacte de les emissions degudes a un gran incendi forestal sobre la ciutat.
S’han utilitzat eines quimiomètriques per extreure millor la informació acumulada a les bases de dades generades i així conèixer les fonts de contaminació atmosfèrica possibles a Madrid i Barcelona. la font principal de contaminants atmosfèrics és el trànsit. La crema de biomassa és una altra font contaminant molt important a l’hivern, en canvi a l’estiu predominen compostos secundaris formats a partir dels compostos orgànics volàtils emesos per les fonts biogèniques, que reaccionen amb agents oxidants i/o fotoquímics per formar productes d’oxidació, com per exemple els derivats polars de l’isoprè, l’α-pinè i els àcids carboxílics.<br>This study has been performed in the framework of the research project AERTRANS, supported by the Spanish Ministry of Economy and Competitiveness (Plan Nacional de I+D+i CTQ2009-14777-C02-01). Specifically, this thesis is focused on the study of chemical composition and emission sources of organic matter in atmospheric ultrafine fraction of atmospheric aerosols PM1 (particles with aerodynamic diameter <1μm) in urban areas with high pollution levels. Madrid and Barcelona were selected based on their high pollution levels and their situation in southern Europe, characterized by high solar insolation but different meteorological conditions.
Air was sampled in cold and hot periods during a week taking two samples per day and simultaneous sampling at street level and at 50 m above ground level, in order to investigate pollution sources, seasonal differences and atmospheric processes related to diurnal and weekly cycles and secondary aerosol generation. It has been developed and optimized an analytical methodology for a broad spectrum analysis of organic compounds in PM1 samples, which includes a pressurized liquid extraction with organic solvents (dichloromethane and methanol), followed by a filtration step, purification by normal phase high performance liquid chromatography and subsequent analysis by gas chromatography coupled to mass spectrometry. The main compounds found in the studied aerosol were n-alkanes, polycyclic aromatic hydrocarbons, hopanes, monosaccharide anhydrides (levoglucosan, mannosan and galactosan), carboxylic and dicarboxylic acids, and secondary compounds related to the photooxidation of isoprene and α-pinene. In the case of levoglucosan and its isomers, the analytical methodology was further validated through the participation in an interlaboratory exercise at European scale. In this sense, these biomass burning markers allowed to assess the impact of the emissions from an important forest fire occurred in July 2012, in the atmosphere of Barcelona.
Through the use of chemometric tools, it has been possible to establish the main anthropogenic pollution sources in both cities, related to traffic emissions. Biomass burning is also a significant source, mainly in winter, whereas in summer predominate secondary compounds generated from biogenic volatile organic compounds, which react with oxidizing agents and/or photochemically, this is the case of oxygenated derivatives of isoprene and α- pinene.
27
Hsieh, Wei-Chun. "Representing droplet size distribution and cloud processes in aerosol-cloud-climate interaction studies." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29619.
Full textAbstract:
Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2009.<br>Committee Chair: Athanasios Nenes; Committee Member: Andrew G. Stack; Committee Member: Irina N. Sokolik; Committee Member: Judith A. Curry; Committee Member: Mike Bergin; Committee Member: Rodney J. Weber. Part of the SMARTech Electronic Thesis and Dissertation Collection.
28
Johnson, Graham Richard. "The Formation and Growth of Marine Aerosols and the Development of New Techniques for their In-situ Analysis." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16117/.
Full textAbstract:
Marine aerosols have attracted increasing attention over the past 15 years because of their potential significance for global climate modelling. The size distribution of these aerosols extends from super-micrometer sea salt mode particles down through 150 nm accumulation mode particles, 40 nm Aitken mode particles and nucleation mode particles which extend from 25 nm right down to clusters of a few molecules. The process by which the submicrometer modes form and grow and their composition have remained topics of debate throughout this time in large part because of the difficulties associated with determining their composition and relating it to proposed models of the formation process. The work compared the modality of marine aerosol influencing the South-east-Queensland region with that of other environmental aerosols in the region. The aerosol was found to be consistent with marine aerosols observed elsewhere with concentrations below 1000 cm-3 and frequently exhibiting the distinct bimodal structure associated with cloud processing, consisting of an Aitken mode at approximately 40 nm, an accumulation mode in the range 100-200 nm and a coarse mode attributed to sea salt between 600 and 1200 nm. This work included the development of two new techniques for aerosol research. The first technique measures aerosol density using a combination of aerosol size distribution and gravimetric mass concentration measurements. This technique was used to measure the density of a number of submicrometer aerosols including laboratory generated NaCl aerosol and ambient aerosol. The densities for the laboratory generated aerosols were found to be similar to those for the bulk materials used to produce them. The technique, extended to super-micrometer particle size range may find application in ambient aerosol research where it could be used to discriminate between periods when the aerosol is dominated by NaCl and periods when the density is more representative of crustal material or sulfates. The technique may also prove useful in laboratory or industrial settings for investigating particle density or in case where the composition is known, morphology and porosity. The second technique developed, integrates the existing physicochemical techniques of volatilisation and hygroscopic growth analysis to investigate particle composition in terms of both the volatilisation temperatures of the chemical constituents and their contribution to particle hygroscopic behaviour. The resulting volatilisation and humidification tandem differential mobility analyser or VH-TDMA, has proven to be a valuable research tool which is being used in ongoing research. Findings of investigations relating the composition of the submicrometer marine aerosol modes to candidate models for their formation are presented. Sea salt was not found in the numerically dominant particle type in coastal nucleation mode or marine Aitken and accumulation modes examined on the Southeast Queensland coast during periods where back trajectories indicated marine origin. The work suggests that all three submicrometer modes contain the same four volatile chemical species and an insoluble non-volatile residue. The volatility and hygroscopic behaviours of the particles are consistent with a composition consisting of a core composed of sulfuric acid, ammonium sulfate and an iodine oxide coated with a volatile organic compound. The volume fraction of the sulfuric acid like species in the particles shows a strong dependence on particle size.
29
Calderón, Mateo Patricia Evelin. "Influencia del transporte de concentración de Pm10 en el espesor óptico de aerosoles de la ciudad de Huancayo en el año 2015-2016." Bachelor's thesis, Universidad Continental, 2018. http://repositorio.continental.edu.pe/handle/continental/4686.
Full textAbstract:
La investigación se centra en destacar cual es el transporte de las emisiones de Pm10 generados por la quema de vegetación en el Perú y países vecinos tales como Brasil y Bolivia principalmente; y cómo influyen estas partículas en el espesor óptico de aerosoles (AOD, por sus siglas en inglés) obtenido por el fotómetro solar del Observatorio de Huancayo. Para ello se eligió el mes de agosto de 2015 que es un período caracterizado por ser no lluvioso, y el mes de enero de 2016, período caracterizado por ser lluvioso. De
manera que, se pueda hacer una comparación entre el número de focos de incendios, emisiones producidas por los incendios y cómo afecta en el AOD obtenido por el fotómetro solar del Observatorio de Huancayo; en cada una de estas en los meses referidos líneas arriba. Para determinar el transporte de PM10, se realizó el modelamiento con ayuda del modelo WRF–CHEM, cuya finalidad fue la de obtener datos
de concentración Pm10.
30
Peltier, Richard Edward. "Ambient Submicron Particles In North America: Their Sources, Fate, and Impact." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19750.
Full textAbstract:
Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008.<br>Committee Chair: Weber, Rodney J.; Committee Member: Bergin, Michael H.; Committee Member: Huey, L Gregory; Committee Member: Ingall, Ellery D.; Committee Member: Nenes, Athanasios.
31
Vinchurkar, Samir C. "Numerical Analysis of Respiratory Aerosol Deposition: Effects of Exhalation, Airway Constriction and Electrostatic Charge." VCU Scholars Compass, 2008. http://hdl.handle.net/10156/2014.
Full textAbstract:
Thesis (Ph. D.)--Virginia Commonwealth University, 2008.<br>Prepared for: Dept. of Mechanical Engineering. Includes bibliographical references (leaves 212-233). Also available online via the Internet.
32
Wiston, Modise. "Regional modelling of air quality and aerosol-interactions over southern Africa : impact of aerosols and regional-scale meteorology." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/regional-modelling-of-air-quality-and-aerosolinteractions-over-southern-africa-impact-of-aerosols-and-regionalscale-meteorology(50819acb-590e-4e18-8552-038ec1f2ab78).html.
Full textAbstract:
Atmospheric trace components play a critical role in the earth–atmosphere system through their interaction and perturbation to global atmospheric chemistry. They perturb the climate through scattering and absorbing of solar radiation (direct effects), thereby impacting on the heat energy balance of the atmosphere, and alter cloud microphysical properties affecting cloud formation, cloud lifetime and precipitation formation (indirect effects). These trace components can also have adverse effects on human health, visibility and air quality (AQ) composition, including various feedback processes on the state of the atmosphere. As well as their direct and indirect effects, aerosols are important for cloud formation. They serve as cloud condensation and ice nuclei (CCN and IN) during cloud droplet and ice crystal formations. Although many connections between clouds and aerosol effects have been established in cloud physics and climate modelling, aerosol–cloud interaction (ACI) is still one of the areas of large uncertainties in modern climate and weather projections. Different models have been developed placing much emphasis on ACIs, to have robust and more consistent description processes within the meteorological and chemical variables to account for ACIs and feedback processes. Because pollutant distributions are controlled by a specific meteorology that promotes residence times and vertical mixing in the atmosphere, reliable chemical composition measurements are required to understand the changes occurring in the earth–atmosphere system. Also, because atmospheric pollution is a combination of both natural and man-made (anthropogenic) sources, to direct controlled and/or mitigation procedures efficiently, contributions of different sources need to be considered. Occasionally these are explored from a particular region or global environment, depending on a specific area of interest. A fully coupled online meteorology–chemistry model framework (WRF-Chem) is used to investigate atmospheric ACIs over southern Africa –a region characterized by a strong and intense seasonal biomass burning (BB) cycle. The large transport of aerosol plumes originating from the seasonal burning from agriculture, land-use management and various activities give rise to a unique situation warranting special scrutiny. Simulations are conducted for the 2008 dry season BB episode, implementing a chemical dataset from various emission sources (anthropogenic, BB, biogenic, dust and sea salt) with the meteorological conditions. A base line (CNTRL) simulation was conducted with all emission sources from 26 August to 10 September 2008. To probe the contribution of BB on the regional pollution and influence on ACIs, a sensitivity (TEST) simulation was conducted without BB emissions and compared to the base line. The impact of natural and anthropogenic aerosol particles is studied and quantified for the two simulations, focusing on aerosol concentration and cloud responses under different model resolutions. A statistical analysis of pollutant concentration of major regulated species and cloud variables is conducted and the percentage difference used to assess the contribution due to BB emissions. Results confirm the high variability of spatial and temporal patterns of chemical species, with the greatest discrepancies occurring in the tropical forests whereas the subtropics show more urban/industrial related emissions. Whilst CO and O3 show statistically significant increases over a number of cities/towns, the trend and spatial variability is much less uniform with NO2 and PM in most urban and populous cities. Statistical analysis of major chemical pollutants was mainly influenced by BB emissions. O3, NOx, CO and PM increase by 24%, 76%, 51%, 46% and 41% over the main source regions, whereas in the less affected regions concentrations increased by 5%, 5%, 5%, 3% and 2% when BB emissions are included. This study sheds new light on the response of cloud processes to changing aerosol concentrations and different model resolutions. In the parameterised case (dx = 20 km), clouds become more cellular, correlated with high supersaturations, whereas in the resolved case (dx = 4 km), they become more faint with relatively lower supersaturations. Aerosol effects on cloud properties were further studied and statistical analysis conducted on CCN, cloud droplet number concentration (CDNC), supersaturation and aerosol optical depth (AOD) at two different grid spacings. Most clouds occur to the west of the domain coincident with increase in aerosol concentration and AOD, while single scattering albedo (SSA) decreases. A considerable cloud ‘burn-off’ occurs in tropical west Africa, where aerosols can also be lofted up to 500-hPa level when BB emissions are included in the simulation. Due to BB, absorbing aerosol increased by 76% and 23% over tropical west and subtropical southeast, while tropical east shows no change. The study shows that tropical central Africa is characterized by an increased build-up in biomass burning aerosols (BBAs), forming a regional haze with high AOD; this becomes stronger near active burning areas with a significant proportion occurring to the west. AOD enhancement increases up to 38%, 31% and 11% in the west, east and south respectively. Although CDNC increased in areas with high aerosol concentration, supersaturation decreases (in the small domains) since increase in aerosol number concentration decreases maximum supersaturation Smax. Changes in absorbed radiation increased by +56 Wm-2, +23 Wm-2 and +14 Wm-2 in the west, east and southeast. To further evaluate the model sensitivity and its skill, an analysis was conducted by comparing the model performance with measurement data. Simulated AOD, surface concentrations of CO and O3, ozonesondes and liquid water path (LWP) were compared with measured data from MODIS satellite, SAFARI2000 field study and Cape Point WMO. The model shows a good skill in capturing and reproducing the trends as that measured. However, a severe lack of measurement data over southern Africa makes it more difficult to effectively evaluate WRF-Chem over southern Africa. There is a need for increased availability of measurements to adequately compare with models. This study is one of the first WRF-Chem studies conducted over southern Africa to simulate the weather and pollution interaction. The novelty of the present study is the combined analysis of ACI sensitivity to aerosol loading and cloud response in a regime-based approach. The study concludes with a brief discusssion of future directions for work on AQ and modelling interactions between pollution and weather over southern Africa.
33
Gazdošová, Lucie. "Studium chemického složení atmosférických aerosolů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216356.
Full textAbstract:
Atmospheric aerosols play an important role in various atmospheric issues (effect to the radiation budget of the atmosphere, visibility reduction, smog production, destruction of stratospheric ozone, …). Epidemiological studies proved a correlation between increased mortality and high concentration of ambient particulate matter. Over the past decade, a growing attention has been focused on the organic compounds that are constituents of aerosol particles. Although organic compounds comprise often up to 60% of the total aerosol mass, their composition, concentration and formation mechanisms are not well understood. Diploma thesis will deal with the study of chemical composition of organic compounds bound to atmospheric aerosols with focus on polyaromatic hydrocarbons and sugars. Atmospheric aerosols will be sampled on filters and filter extracts will be analysed for content of studied organic compounds by means of GC, GC-MS or LC, respectively. Development and optimalization of extraction methods (PSE, …) and detection of compounds of interest. Concentration of studied organic compounds in aerosol size fractions PM 10, PM 2.5 and PM 1 will be compared.
34
Boer, Gregory Jon. "Investigation of high spectral resolution signatures and radiative forcing of tropospheric aerosol in the thermal infrared." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34001.
Full textAbstract:
An investigation of the high spectral resolution signatures and radiative forcing of tropospheric aerosol in the thermal infrared was conducted. To do so and to support advanced modeling of optical properties, a high spectral resolution library of atmospheric aerosol optical constants was developed. This library includes new optical constants of sulfate-nitrate-ammonium aqueous solutions and the collection of a broad range of existing optical constants for aerosol components, particularly mineral optical constants. The mineral optical constants were used to model and study infrared dust optical signatures as a function of composition, size, shape and mixing state. In particular, spherical and non-spherical optical models of dust particles were examined and compared to high spectral resolution laboratory extinction measurements. Then the performance of some of the most common effective medium approximations for internal mixtures was examined by modeling the optical constants of the newly determined sulfate-nitrate-ammonium mixtures. The optical signature analysis was applied to airborne and satellite high spectral resolution thermal infrared radiance data impacted by Saharan dust events. A new technique to retrieve dust microphysical properties from the dust spectral signature was developed and compared to a standard technique. The microphysics retrieved from this new technique and from a standard technique were then used to investigate the effects of dust on radiative forcing and cooling rates in the thermal IR.
35
Northcross, Amanda Laura Jang Myoseon. "Secondary organic aerosol SOA formation from monoterpene ozonolysis in the presence of inorganic aerosols acid effects on SOA yields /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1875.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2008.<br>Title from electronic title page (viewed Dec. 11, 2008). "... in partial fulfillment of the requirements for the degree of doctor of philosophy in the Department of Environmental Sciences and Engineering, School of Public Health." Discipline: Environmental Sciences and Engineering; Department/School: Public Health.
36
Ouellet, Jeffrey Ovide. "Models of aerosol backscatter, extinction and absorption profiles for desert aerosols based on aircraft instrument and ground-based lidar measurements." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/30755.
Full text
37
Ripoll, Roca Anna. "Physical, optical and chemical properties of atmospheric aerosols in the western Mediterranean continental background." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/305999.
Full textAbstract:
Atmospheric aerosols have played a key role in the development of the Earth’s atmosphere. Without atmospheric particles rainfall would be nonexistent and the climate would be very different. However, anthropogenic emissions have changed the chemical composition of atmospheric aerosols significantly through emissions of particles and precursor gases, particularly since the industrial revolution. Moreover, numerous studies have demonstrated that atmospheric aerosols, both natural and anthropogenic, do not only influence Earth’s climate, but also have adverse effects on human health, ecosystems, as well as on air quality.
The global distribution of the aerosols is very uneven; therefore atmospheric particles have very different concentrations and composition depending on the region. In southern Europe, and in particular in the western Mediterranean region, the meteorological conditions with higher temperatures and lower precipitation, together with the abrupt topography around the Mediterranean Sea, hinder aerosol dispersion and prevent atmospheric wet-scavenging processes. Moreover, Mediterranean region is highly influenced by both anthropogenic emissions from shipping, power generation, industrial processes and road traffic, among others sources, and natural emissions from African dust outbreaks, soil resuspension, wildfires, sea spray, and vegetation. All these particular and complex atmospheric dynamics result in higher concentrations of aerosols around the Mediterranean Basin than in northern Europe.
A detailed study of the physical, optical and chemical properties of the continental background aerosols measured at Montsec (MSC) monitoring station is presented in this work. The MSC mountain site (1570 m a.s.l.) was established during the development of this thesis; it is located in the western Mediterranean and became a member of the GAW (Global Atmosphere Watch) network in 2014.
Aerosol properties (particle mass (PM), particle number (N), absorption (σap), scattering (σsp) and chemical composition) from MSC were found to be comparable in magnitude to those from other remote sites in Europe, when removing African dust outbreaks influence. This suggests that a continental background designation for MSC site is applicable. Nevertheless, some differences between MSC and other European remote sites highlight the importance of new particle formation (NPF) processes as a source of particles, the lower contribution of combustion and industrial processes, the greater impact of shipping emissions, and the higher influence of biogenic emissions. Moreover, these differences corroborate the important contribution of long-range transport of mineral dust and reveal a high impact of regional dust resuspension in the western Mediterranean region.
Continental background aerosols in this region are affected by natural and anthropogenic emissions which results in a PM1 (PM of diameter less than 1 µm) comprised of (in decreasing concentrations) organic matter, sulfate, ammonium, mineral matter, nitrate, elemental carbon, sea salt and trace elements. The foremost PM1-10 (PM of diameter between 1 and 10 µm) constituent is mineral matter, followed by organic matter, nitrate, sulfate, sea salt, ammonium and elemental carbon. Comparison of σap measurements with those of elemental carbon revealed an average mass absorption cross section (MAC) at MSC of 9.1 m-2 g-1 .
A clear seasonal variation is observed for the majority of the aerosol parameters measured at MSC, with the highest values in summer and the lowest in winter, except for nitrate, in agreement with previous studies in the western Mediterranean. The reduced human activity at the weekend is reflected in the concentrations of PM1 and BC with a delay of one day (minimum on Sunday and Monday), which confirms that MSC is located at a sufficient distance from direct anthropogenic emissions, although it is still affected by them. The intra-day variation of PMx, BC, σsp and PM1 major inorganic components (sulfate, nitrate, ammonium and chloride) shows poorly defined daily patterns in summer but clearer in winter, whereas concentrations of N and submicron organic aerosol show marked diurnal cycles throughout the year and regardless of the air mass origin, with a clear increase around midday.<br>Els aerosols atmosfèrics han jugat un paper crucial en el desenvolupament de l’atmosfera terrestre. Sense les partícules atmosfèriques la pluja no hauria existit i el clima seria molt diferent. No obstant això, les emissions antropogèniques han canviat de forma significativa la composició química dels aerosols atmosfèrics degut a l’emissió de partícules i de gasos precursors. A més a més, nombrosos estudis han demostrat que els aerosols atmosfèrics, tant naturals com antropogènics, no només influencien el clima de la Terra, sinò que també provoquen efectes perjudicials per la salut humana, els ecosistemes i la qualitat de l’aire.
En aquesta tesi doctoral es presenta un estudi detallat de les propietats físiques, òptiques i químiques dels aerosols de fons continental mitjançant les mesures realitzades a l’estació del Montsec (MSC, 1570 m s.n.m.). Aquesta estació de muntanya està situada a l’oest del Mediterrani, es va establir durant el desenvolupament d’aquesta tesi i forma part de la xarxa GAW (Global Atmosphere Watch) des de 2014.
Les propietats dels aerosols (massa (PM), nombre (N), absorció (σap), dispersió (σsp) i composició química) mesurades al MSC van presentar magnituds comparables a les obtingudes a altres llocs remots d’Europa, una vegada eliminada la influència de les intrusions de pols sahariana. Per tant, la designació de fons continental és aplicable per a l’estació del MSC. Tanmateix, algunes diferències entre les propietats mesurades al MSC i les mesurades a altres estacions remotes europees van revelar que els processos de formació de noves partícules (angl., new particle formation, NPF) com a font de partícules són molt importants a la regió oest del Mediterrani. També van destacar que els processos industrials i de combustió tenen una menor contribució a la matèria particulada (angl., particulate matter, PM) ambiental, mentre que les emissions biogèniques i dels vaixells tenen un major impacte. A més a més, van corroborar que el transport de llarga distància de la pols del Sàhara és la font natural de partícules més important en aquesta regió, i van revelar que la pols de resuspensió regional té un impacte considerable.
38
Bachour, Dunia Antoine. "Measuring and estimating solar direct normal Irradiance using LIDAR, solar station and satellite data in qatar." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/310413.
Full textAbstract:
La medición precisa de la Irradiancia Directa Normal (DNI) es esencial para el diseño e
implementación de proyectos CSP (energía solar concentrada). Qatar cuenta con abundante
radiación solar; por lo tanto, el aprovechamiento de la misma es de gran interés en esta región, en
particular para sistemas de concentración solar. Antes de embarcarse en dichos proyectos, se
debe contar con datos de irradiancia directa normal confiables y de buena calidad. Actualmente,
los mapas existentes de radiación solar en Qatar basados en mediciones a nivel de la superficie
terrestre son rudimentarios. Los mapas solares basados en datos de satélite proveen una mayor
cobertura espacial, pero con resoluciones espacial y temporal relativamente pobres, además de
que los datos satelitales de radiaion solar aun no han sido calibrados con mediciones directas en
Qatar, por lo que no proveen valores muy precisos de DNI. Por esto, datos confiables basados en
mediciones directas con altas resoluciones son necesarios en regiones como Qatar, con medio
ambiente desértico arenoso y con altas concentraciones de aerosoles. Dependiendo de su
composición, un aerosol puede dispersar o absorber DNI. Entre más aerosoles hay presentes en
el aire, mayor es la dispersión y/o absorción del componente directo de la radiación solar, lo que
reduce la eficiencia de los sistemas de energía solar concentrada. Así, la calidad de la atmósfera
tiene gran impacto sobre la viabilidad de las plantas CSP.
El trabajo presentado en esta tesis se enfoca en el estudio del impacto de la calidad de la
atmósfera en Doha, Qatar, específicamente los aerosoles, sobre la atenuación del haz solar
directo. Esto se realiza por medio de una función de correlación entre la calidad atmosferica y
mediciones de DNI. El resultado de esta correlación puede ser usado para calibrar mapas solares.
Se utilizó un LIDAR para estimar la calidad de la atmósfera por medio de la medición de luz
reflejada por los componentes de la atmósfera. Junto al LIDAR, una estación de monitoreo de la
radiación solar se usó para medir directamente DNI. Con base en los resultados de este trabajo,
los mapas solares de Qatar basados en satélite pueden ser corregidos, lo que permitirá la
elaboración de una base de datos completa del recurso solar en Qatar.<br>Accurate measurements of Direct Normal Irradiance (DNI) are essential to Concentrated Solar
Power (CSP) project design and implementation. Qatar has an abundant supply of solar
radiation; therefore, harnessing solar energy is of particular interest in this region specifically for
concentrated solar power systems. Before such projects are undertaken, good quality and reliable
Direct Normal Irradiance of solar radiation data must be available. Existing solar energy maps of
Qatar based on ground station measurements are primitive. Solar energy maps based on satellite
data have a wider spatial coverage but relatively poor temporal and spatial resolutions, and
satellite-derived solar data have not been calibrated with ground measurements in Qatar, and thus
cannot provide accurate DNI. Therefore, reliable data based on high resolution ground
measurements are required specifically for a country like Qatar, a region of harsh desert
environment with dusty climate and high aerosol loads. Depending on its composition, an
aerosol can scatter and/or absorb the DNI. The more aerosols in the air, the more scattering
and/or absorption of the direct component of the solar radiation will take place and this will
reduce the effectiveness of a concentrated solar power system. The quality of the atmosphere has
thus a great impact on the viability of CSP farms.
The work presented in this thesis is focused on studying the impact of the quality of the
atmosphere in Doha, Qatar, specifically aerosol particles, on the solar direct beam attenuation.
This is done by establishing a correlation function between the quality of the atmosphere and the
measured DNI. The result of this correlation may be used to calibrate satellite solar maps. A
LIDAR device is used to estimate the quality of the atmosphere by measuring the light
backscattered by the constituents of the atmosphere. Beside the LIDAR, a Ground Solar
Radiation Monitoring Station is used to measure directly the DNI. Based on the result of this
work, satellite-derived solar maps of Qatar can be corrected and this will allow building a
comprehensive solar radiation database for Qatar.
39
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 textAbstract:
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.
40
Mårtensson, Monica. "Submicrometre aerosol emissions from sea spray and road traffic." Doctoral thesis, Stockholm University, Department of Meteorology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7006.
Full textAbstract:
<p>The uncertainty of the climate and health effects of aerosols is still large, one important reason being lack of knowledge of the primary emissions. This thesis combines laboratory and field experiments, and process modelling in an effort to better quantify the submicrometre aerosol emissions and to understand some of the processes in the atmosphere.</p><p>A parameterisation was derived for the source flux of sea salt particles (particles m<sup>-2 </sup>s<sup>-1</sup>) in the size range 0.02-2.8 µm dry diameter (D<sub>p</sub>), it is the first parameterisation to almost cover two full decades of the submicrometre sea salt aerosol production, and to include the effect of water temperature. This sea salt parameterisation was validated for temperate water in the 0.1-1.1 μm D<sub>p</sub> range using in situ size resolved emissions of marine aerosol particles, which were measured with the eddy covariance (EC) method. For periods sampled air was heated to 300ºC in order to evaporate semi-volatile organics and isolate the sea salt fraction. Comparisons with the total aerosol emissions suggest that in these emissions organic carbon and sea salt are internally mixed in the same particles. Finally an aerosol dynamics model was modified for marine conditions. In the model parameterised emissions of sea salt was included together with aerosol dynamics, chemistry and clouds representative for the marine boundary layer. The sea salt emissions are together with secondary sulphate, and cloud processing able to reproduce a typical marine aerosol size distribution and cloud condensation nuclei population.</p><p>Measurements with the EC method of the road traffic related aerosol source number flux for D<sub>p</sub>>0.011 µm show that the major part of the aerosol fluxes is due to road traffic emissions. Both an emission factor for the whole fleet mix in Stockholm (1.4x10<sup>14</sup> vehicle<sup>-1</sup> km<sup>-1</sup>) and separate emission factors for light- and heavy-duty vehicles (HDV) were deduced. The result shows that during weekdays 70-80% of the emissions come from HDV.</p>
41
Young, Dominique Emma. "Characterisation of the chemical properties and behaviour of aerosols in the urban environment." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-the-chemical-properties-and-behaviour-of-aerosols-in-the-urban-environment(27de7e50-5069-40a0-b5cd-1370747f646a).html.
Full textAbstract:
Atmospheric aerosols have adverse effects on human health, air quality, and visibility and frequently result in severe pollution events, particularly in urban areas. However, the sources of aerosols and the processes governing their behaviour in the atmosphere, including those which lead to high concentrations, are not well understood thus limit our ability to accurately assess and forecast air quality. Presented here are the first long-term chemical composition measurements from an urban environment using an Aerodyne compact Time-of-Flight Aerosol Mass Spectrometer (cToF-AMS). Organic aerosols (OA) were observed to account for a significant fraction (44%) of the total non-refractory submicron mass during 2012 at the urban background site in North Kensington, London, followed by nitrate (28%), sulphate (14%), ammonium (13%), and chloride (1%). The sources and components of OA were determined using Positive Matrix Factorisation (PMF) and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2), where HOA, COA, and SFOA were observed to be of equal importance across the year. The concentration of secondary OA increased during the summer yet the extent of oxidation, as defined by the oxygen content, showed no variability during the year. The main factors governing the diurnal, monthly, and seasonal trends observed in all organic and inorganic species were meteorological conditions, specific nature of the sources, and availability of precursors. Regional and transboundary pollution influenced total aerosol concentrations and high concentration events were observed to be governed by different factors depending on season. High-Resolution ToF-AMS measurements were used to further probe OA behaviour, where two SFOA factors were derived from PMF analysis in winter, which likely represent differences in burn conditions. In the summer an OA factor was identified, likely of primary origin, which was observed to be strongly associated with organic nitrates and anthropogenic emissions. This work uses instruments and techniques that have not previously been used in this way in an urban environment, where the results further the understanding of the chemical components of urban aerosols. Aerosol sources are likely to change in the future with increases in solid fuel burning as vehicular emissions decrease, with significant implications on air quality and health. Thus it is important to understand aerosol sources and behaviour in order to develop effective pollution abatement strategies.
42
Leite, Eduardo Manuel de Almeida. "Cooperação empresarial: o caso Aerosoles." Master's thesis, [s.n.], 2003. http://hdl.handle.net/10284/4984.
Full textAbstract:
Dissertação apresentada à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Empresariais<br>A arquitectura económica mundial alterou-se substancialmente nas duas últimas décadas, sendo actualmente caracterizada pela mudança, desmaterialização e globalização. Neste quadro, as empresas deparam-se com crescentes dificuldades de adaptação que afectam o seu comportamento e fazem ressaltar a necessidade de cooperação.
Cooperar significa instituir relações privilegiadas entre empresas na procura conjunta de inovações que possam contribuir para alcançar um objectivo comum. O conceito é suficientemente abrangente, podendo ir desde o aprofundamento duma simples relação fornecedor-cliente até ao desenvolvimento de estruturas de mercados baseadas no estabelecimento de redes de empresas. No entanto, os casos mais típicos são as joint ventures, as fusões e aquisições, a subcontratação, o franchising e as licenças de exploração.
Tendo por base o tema da cooperação definiu-se como objectivo geral do presente trabalho a análise crítica do paradigma da cooperação empresarial como método de desenvolvimento estratégico, em especial externo, na indústria portuguesa do calçado, através do estudo de um dos grupos mais representativos da referida indústria, o Grupo Aerosoles.
No âmbito deste objectivo, desenvolveu-se um estudo do tipo descritivo e com uma estratégia baseada no estudo de caso recorrendo-se à entrevista, suportada por um questionário e à análise de dados secundários, como métodos de recolha de dados, sendo estes últimos obtidos a partir de fontes privadas e públicas.
Os resultados do estudo à cooperação empresarial no Grupo Aerosoles revelaram a existência de dois acordos de cooperação celebrados, um entre a What’s What Portugal, Comércio e Desenvolvimento de Calçado S.A. e a Aerogroup International Inc.; e outro entre a Aeroshoes, Distribuidores de Calçado S.A., a Aerogroup International Inc. e o FIEP, Fundo para a Internacionalização das Empresas Portuguesas, SGPS, S.A. Ambos os acordos de cooperação são internacionais, devido à nacionalidade das empresas parceiras (Norte Americanas) e enquadram-se no sector comercial. Conclui-se ainda neste estudo, que a cooperação não se pode dissociar do sucesso do Grupo Aerosoles.
The world economic architecture has substantially altered in the last two decades, nowadays being characterized by change, dematerialization and globalization. In this picture, the enterprises come across with increasing difficulties of adaptation that influence their behaviour and makes necessity of cooperation to stand up.
To cooperate means to establish preferential relation between the demands in enterprises combined with innovations that can contribute to attain a common aim. The concept is sufficiently all embracing, being able to go from the bottom of a simple relation of supplier-customer till the development of market structures based on the enterprise system establishment. Meanwhile, the typical cases are the joint ventures, the fusions and acquisitions, the sub contraction, the franchising and the licences.
Having as basis the cooperation’s theme, we defined as the general objective of the present work, the critical of paradigm of enterprise cooperation as a method of strategic development, in especial external, in portuguese industry of foot-wear through a study of one of the most representative groups of the aforementioned industry, the Aerosoles Group.
In the ambit of this objective, it was developed a descriptive type of study and with a strategy based on case study resorting an interview, supported by a questionnaire and from the analyses of secondary data, as gathering data methods, these last ones being obtained from private and public sources.
The study results enterprise cooperation on Aerosoles Group, revealed a existence from two honoured cooperation agreements, one between the What’s What Portugal, Comércio e Desenvolvimento de Calçado S.A., and Aerogroup International Inc., and the other between the Aeroshoes, Distribuidores de Calçado S.A., The Aerogroup International Inc. and the FIEP, Fundo para a Internacionalização das Empresas Portuguesas, SGPS, S.A. Both of the cooperation agreements are international, due to the enterprise’s partnership nationality (North Americans) and they put in frame the commercial sector. Yet in this study we can conclude that the cooperation cannot be dissociated from the Aerosoles Group.
L’architecture économique du monde a changée substantiellement pendant les deux dernières décades et actuellement elle se caractérise par la changement, la dématérialisation et la globalisation. Dans ce milieu, les entreprises trouvent croissantes difficultés d’adaptation, lesquelles affectent sas conduite et ressautent la nécessité de coopération.
Coopérer signifie instituer relations privilégiées entre entreprises dans la recherche conjoint d’innovations, lesquelles puissent contribuer pour atteindre un objectif commun. Le concept est assez suffisant, en passant dès l’approfondir d’une simple relation fournisseur client jusqu’à le développement de structures de marché, s’appuyant dans l’établissement de filets d’entreprises. Entre-temps, les situations plus typiques sont les joint-ventures, les fusions e acquisitions, le sous-traitance, franchising et les licences d’exploration.
Prenant le thème de la coopération, on a défini comme objectif général du présent travail l’analyse critique du paradigme de la coopération de l’entreprise comme méthode de développement stratégique, particulièrement externe, dans l’industrie portugaise de chaussure, a travers de l’étude d’un des groups plus représentatifs de la précitée industrie, le Grupo Aerosoles.
Dans le contour de cet objectif, nous avons développé un étude du type descriptif et avec une stratégie fondée dans l’étude d’un cas. Nous avons utilisé l’entrevue, supportée par questionnaire, et à l’analyse de dés secondaires, comme méthodes de recueille de dés, ces derniers obtenues à partir de sources privées et publiques.
Les résultats de l’étude sur la coopération d’entreprises dans le Grupo Aerosoles ont révèles l’existante de deux accords de coopération célèbres, l’un entre What’s What Portugal, Comércio e Desenvolvimento de Calçado, S.A. et Aerogroup International Inc. ; et l’outre entre Aeroshoes, Distribuidores de Calçado, S.A., Aerogroup International Inc. et FIEP, Fundo para a Internacionalização das Empresas Portuguesas, SGPS, S.A. Les deux accords de coopération sont internationales, dû à la nationalité des entreprises associées (Amérique du Nord) et ils s’encadre dans le secteur commercial.
On conclu aussi de cet étude que la coopération ne peux pas être dissociée du succès du Grupo Aerosoles.
43
Huamán, Bravo Rolando Anibal. "Nivel de conocimiento y aplicación de las medidas preventivas para reducir el riesgo de enfermedades transmisibles a través de los aerosoles en alumnos de la Facultad de Odontología de la UNMSM." Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2004. https://hdl.handle.net/20.500.12672/2778.
Full textAbstract:
Se realizó un estudio para determinar el nivel de conocimiento y aplicación de medidas preventivas para reducir el riesgo de transmisión de enfermedades a través de aerosoles, en los alumnos que llevan clínica en la Facultad de Odontología de Universidad Nacional Mayor de San Marcos.
Se tomó una muestra de 70 alumnos, los cuales fueron escogidos al azar para ser evaluados en cuanto al nivel de conocimiento y aplicación de las medidas preventivas frente a la exposición de los aerosoles.
Se evaluó el nivel de aplicación por medio de la observación del comportamiento de los alumnos en la clínica odontológica durante la atención a sus pacientes de acuerdo a los ítems mencionados en una lista de cotejos previamente diseñada.
La evaluación del nivel de conocimiento, se realizó por medio del desarrollo de un test que constaba de 14 preguntas y que tuvo una duración de 10 a 15 minutos.
Una vez obtenidos los datos se procedió a la calificación de las pruebas y listas de cotejos, haciéndose las tabulaciones y cálculos correspondientes encontrándose los siguientes resultados:
Se encontró un conocimiento entre regular y bueno por parte de los alumnos sobre las medidas preventivas con 91,40% de los casos, el nivel de aplicación de dichas medidas no se cumplen en la mayoría de los casos observados, no pudo encontrarse una relación estadísticamente significativa entre el nivel de conocimiento y nivel de aplicación de las medidas preventivas frente a la exposición de los aerosoles.<br>Tesis
44
Elcner, Jakub. "Transport a depozice aerosolu v dýchacím traktu člověka." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-234603.
Full textAbstract:
One of approaches in treatment of respiratory system diseases is the use of drug particles suspended in air in the form of aerosol. It is a fast and non-invasive method for the delivery of medicine into tracheobronchial tree or bloodstream. Although the method of the medication dosage by means of inhalers or nebulizers is well known, the effectiveness of that approach is still an actual issue. A significant amount of drugs delivered with the use of the medication dosage never reaches its primary destination and the drugs deposit in antecendent areas of respiratory tract where their presence is not required. This thesis deals with a problem of the passage of monodisperse homogenous aerosol with micron-size particles through the upper parts of the respiratory tract. This work was created with the use of numerical simulations carried out by means of the finite volume method in the commercial code based on computational fluid dynamics. Turbulence was modelled using the Reynolds averaged Navier–Stokes equations with the two-equation eddy viscosity k-omega SST model. The main output of the thesis is the analysis of airflow in two respiratory regimes. Stationary and cyclic cases of the flow behaviour were considered and the validation of simulated results with experiments performed on similar geometries was carried out. Furthermore, the review of simplified lung models and their geometries was made and the acquired results were used for the calculation of air distribution in the respiratory tract. The last part of the thesis deals with the calculation of particle deposition and with the analysis of the results.
45
Wendisch, Manfred, and Dagmar Rosenow. "ACRIDICON-Zugspitze field campaign." Universität Leipzig, 2013. https://ul.qucosa.de/id/qucosa%3A16413.
Full textAbstract:
From September 17 to October 5, 2012, a field campaign with focus on clouds, aerosols, radiation and dynamics and their interaction in clouds that was coordinated and organized by the Leipzig Institute for Meteorology took place at the Zugspitze mountain.<br>Vom 17. September bis 5. Oktober wurde vom Leipziger Institut eine Feldkampagne zur Untersuchung der Wechselwirkung von Aerosolen, Niederschlag und Strahlung insbesondere in Hinblick auf konvektive Wolken auf der Zugspitze koordiniert und organisiert.
46
Ma, Yilin. "Developments and improvements to the particle-into-liquid-sampler (PILS) and its applications to Asian outflow studies." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131244/unrestricted/ma%5Fyilin%5F200405%5Fphd.pdf.
Full text
47
Gross, Benjamin. "Lithogenic, Marine and Anthropogenic Aerosols in an Ice Core from the Saint Elias Mountains, Yukon, Canada: Lead-Aerosol Provenance and Seasonal Variability." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/GrossB2008.pdf.
Full text
48
Vargas, Gargate Penélope. "Variabilidad espacial y temporal del espesor óptico de los aerosoles sobre Perú usando imágenes de satélite." Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2009. https://hdl.handle.net/20.500.12672/14599.
Full textAbstract:
Realiza un estudio sobre la variabilidad espacial y temporal del espesor óptico de los aerosoles, sobre las regiones geográficas 0º - 20ºS, 90º - 70ºW que pertenece a la zona del Perú y 3º - 8ºS, 82º - 79ºW que abarca la costa norte del Perú. Se utilizaron datos imágenes satelitales procedentes de los sensores MODIS, que se encuentran a bordo de los satélites AQUA y TERRA, del sensor SeaWiFS que se encuentra a bordo del satélite SeaStar, del sensor MISR que se encuentra a bordo del satélite TERRA, y del sensor MERIS que se encuentra bordo del satélite ENVISAT. Se realizaron cálculos de correlaciones, se graficó el coeficiente de Angström versus el espesor óptico del aerosol, para poder clasificar los tipos de aerosoles presentes en la atmósfera de las regiones en estudio. La humanidad ha causado en la naturaleza muchos cambios que no necesariamente han sido favorables para ésta. La atmósfera cada vez presenta más contaminación. Las partículas contaminantes provienen del desarrollo industrial, de los fenómenos propios de la naturaleza, como las erupciones volcánicas, los grandes incendios forestales y de las nuevas partículas que se crean debido a procesos físico-químicos en la propia atmósfera. Los aerosoles son partículas que se encuentran presentes en la atmósfera, que pueden influir sobre el clima. Pueden producir calentamiento al absorber la radiación que incide sobre la atmósfera o pueden provocar enfriamiento al reflejarla parcialmente. También el tamaño de estas partículas cumple un rol importante en la formación de los distintos tipos de nubes ya que facilitan el proceso de condensación de vapor de agua en la atmósfera.<br>Trabajo de suficiencia profesional
49
Hite, James Ricky. "Interpreting thermodenuder data with an optimizing instrument model." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45939.
Full textAbstract:
Secondary organic aerosol (SOA) generated through the partitioning of gas phase volatile organic carbon compounds (VOCs) into the condensed phase has both epidemiological and climatic impacts through the growth of particulate matter into relevant sizes for respiratory interactions and cloud condensation nuclei activity. Considering the complex chemistry involved with VOC oxidation and subsequent formation of SOA, bulk properties like oxidation state, often represented by O:C ratio, and volatility are used to simplify the representation of SOA in chemical transport models (CTMs) and the like [e.g. Tsimpidi et al. 2010]. This preference for bulk properties is supported by the availability of ambient measurement techniques to constrain model parameters and scenarios. The volatility of SOA is often described by treating it as a mixture of components with differing partitioning coefficients through the volatility basis set (VBS) approach rather than explicitly resolving the complex chemistry [Donahue et al., 2006]. This study presents a method of determining the volatility of an aerosol sample through the use of an optimizing thermodenuder (TD) instrument model that is used to fit laboratory data. Data collected using a volatility tandem differential mobility analyzer (VTDMA) setup consist of inlet and outlet particle size and number concentrations for select dicarboxylic acids - compounds known to contribute to atmospheric SOA. These are interpreted by the model through an iterative optimization routine to obtain estimates of volatility parameters (e.g. saturation concentrations) which are compared to available literature data. The instrument model is currently divided into two decoupled modules. The first resolves the flow field characteristics, obtaining the temperature profile, pressure variations, and radial velocity distribution of the TD, and the second resolves the gas to particle partitioning of aerosol with a given condensed-phase volatility distribution in the TD using the VBS approach as described in the literature. Solving the full hydrodynamic equations for the flow characteristics provides a better numeric representation of entry length and radial velocity variations and is an improvement over similar TD modeling studies in the literature. However, results indicate that coupling the two modules is necessary to more accurately resolve the suppression of evaporation due to buildup of organic vapors in the TD, even at the low mass concentrations involved with the presented experiments.
50
Mullins, Benjamin James, and n/a. "Study of Capture, Fibre Wetting and Flow Processes in Wet Filtration and Liquid Aerosol Filtration." Griffith University. School of Environmental Engineering, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040919.124658.
Full textAbstract:
This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations.