O Brasil possui a sétima maior reserva geológica de urânio do mundo, com aproximadamente 310 mil toneladas. A Província Uranífera de Lagoa Real, na região de Caetité e Lagoa Real, situado no centro sul da Bahia, é considerada a mais importante província monominerálica do Brasil. A população urbana que vive no distrito uranífero nas cidades de Caetité, Lagoa Real e Livramento de Nossa Senhora usa água potável oriunda do abastecimento público. Na área rural, caracterizada por freqüentes secas, os moradores recebem água de poços escavados e perfurados como também, de pequenas barragens e reservatórios abastecidos pelas chuvas. Este trabalho determinou os níveis de radioatividade alfa e beta total e as concentrações de urânio em diversos tipos de água consumidas pela população urbana e rural da Província Uranífera de Lagoa Real. As atividades α e β total foram determinadas com detector proporcional de fluxo gasoso e baixa radiação de fundo. As concentrações de urânio foram determinadas com o Espectrômetro de Massa com Fonte de Plasma Indutivo (ICP-MS). Os resultados obtidos foram comparados com as recomendações recentes de 2011 da Organização Mundial da Saúde, a portaria nº 2914 de 12/12/2011 do Ministério da Saúde e as resoluções do CONAMA. Os níveis de radiação natural variaram de 0,0041 ± 0,0004 Bq.L-1 a 0,80 ± 0,04 Bq.L-1 para a atividade alfa total e de 0,045 ± 0,003 a 3,0 ± 0,2 Bq.L-1 para a atividade beta total. Tendo como parâmetro a OMS e o MS, apenas duas amostras de água subterrânea, uma localizada na cidade de Lagoa Real e outra na cidade de Caetité apresentaram concentrações alfa total acima do valor de 0,5 Bq.L-1 descrito em suas recomendações, 0,80 ± 0,04 Bq.L-1 e 0,57 ± 0,03 Bq.L-1respectivamente. Para beta total, três amostras apresentaram níveis de radioatividade acima do limite de 1 Bq.L-1 recomendado pela Organização Mundial de Saúde e estabelecido pelo Ministério da Saúde; 3,0 ± 0,2 Bq.L-1; 1,63 ± 0,13 Bq.L-1 e 1,19 ± 0,07 Bq.L-1 todos situados no município de Lagoa Real. Duas amostras de água subterrânea no município de Caetité apresentaram concentrações de urânio acima do valor de 15 μg.L-1 determinado pelo CONAMA, 20,3 ± 0,3 μg.L-1 e 17,1± 0,3 μg.L-1. Em Lagoa Real, uma amostra apresentou níveis de urânio seis vezes superior ao limite estabelecido pelo Conselho Nacional de Meio Ambiente, 89,5 ± 1,5 μg.L-1. A Organização Mundial da Saúde em 2004 estabeleceu em suas recomendações o limite de 15 μg.L-1 como a concentração máxima de urânio na água potável. Em 2011 a OMS aumentou este limite para 30 μg.L-1. Levando-se em consideração as atuais recomendações da OMS, apenas a concentração de uma amostra de água apresentou níveis de urânio acima do recomendado, 89,5 ± 1,5 μg.L-1 no município de Lagoa Real. / Brazil has the seventh greatest geological uranium reserve in the world with approximately 310 thousand tons. The Lagoa Real Uranium Province, in the region of Caetité and Lagoa Real, situated in South Center Bahia, is considered the most important monomineralic province in Brazil. Urban population who lives in the uranium district in the cities of Caetité, Lagoa Real and Livramento de Nossa Senhora uses drinking water originated from public supply. In the rural area, characterized by frequent draughts, residents receive water from digged and drilled wells and from small dams and reservoirs, as well, which are supplied by the rains. This work determined the levels of total alpha and beta radioactivity and the uranium concentrations in several kinds of water consumed by urban and rural population from the Lagoa Real Uranium Province. Total α e β activities were determined with a low-level gas flow proportional detector. The uranium concentrations were determined with an inductive coupled plasma-mass spectrometer (ICP-MS). The results obtained were confronted with the latest World Health Organizations recommendations from 2011, the ordinance number 2914 of December 12 2011 from the Health Ministry and CONAMAs resolutions. Natural radiation levels varied from 0,0041 ± 0,0004 Bq.L-1 to 0,80 ± 0,04 Bq.L-1 for total alpha activity and from 0,045 ± 0,003 to 3,00 ± 0,2 Bq.L-1 for total beta activity. Having the WHO and the HM as parameter, just two underground water samples, one located in the city of Lagoa Real and the other in the city of Caetité presented total alpha concentration above the value of 0,5 Bq.L-1 described in its recommendations, 0,80 ± 0,040 Bq.L-1 and 0,57 ± 0,03 Bq.L-1 respectively. For total beta three samples presented radioactivity levels above the 1 Bq.L-1 limit recommended by the WHO and established by the Health Ministry; 3,00 ± 0,2 Bq.L-1; 1,63 ± 0,13 Bq.L-1 and 1,19 ± 0,07 Bq.L-1., all of them situated in the Lagoa Real town. Two samples of underground water from Caetité presented uranium concentrations above the value of 15 μg.L-1 determined by CONAMA, 20,3 ± 0,3 μg.L-1 and 17,1± 0,3 μg.L-1. In Lagoa Real one sample presented uranium levels six times over the limit established by the Environment National Council 89,5 ± 1,5 μg.L-1. In 2004 the World Health Organization established in its recommendations the 15 μg.L-1 limit as the maximum uranium concentration in drinking water. In 2011 the WHO increased that limit to 30 μg.L-1. Taking into account the current WHO recommendations only the concentration of one water sample presented uranium levels above the recommended, 89,5 ± 1,5 μg.L-1 in Lagoa Real.

Ge-Sb-Te basierte Phasenwechselmaterialen sind vielersprechende Kandidaten für die Anwendung in optischen und elektrischen nicht-flüchtigen Speicheranwendungen. Diese Materialien können mit Hilfe von elektrischen oder optischen Pulsen reversibel zwischen der kristallinen und amorphen Struktur geschaltet werden. Diese stukturellen Phasen zeigen einen großen Unterschied in ihren elektronischen Eigenschaften, der sich in einer starken Änderung der optischen Reflektivität und des elektrischen Widerstands zeigt.Diese Studie befasst sich mit epitaktischem Wachstum und Analyse der epitaktischen Schichten. Der erste Teil der Arbiet befasst sich mir dem epitaktischen Wachstum von GeTe. Dünne GeTe Schichten wurden auf Si(111) und Si(001) Substraten mit einer Gitterfehlanpassung von 10.8% präpariert. Auf beiden Substraten bildet sich in der GeTe Schicht die [111] Oberflächenfacette parallel zur Si(001) und Si(111) Oberfläche aus. Während des inertialen Wachstums findet eine Phasentransformation von amorph zu kristallin statt. Diese Phasentransformation wurde mittels azimuthaler in-situ Beugung hochenergetischer Elektronen sowie in-situ Röntgenbeugung unter streifendem Einfall untersucht. Der zweite Teil der Arbeit wird die Epitaxie sowie die strukturelle Charakterisierung dünner Sb2Te3 Schichten dargestellt. Der dritte Teil umfasst die Epitaxie terniärer Ge-Sb-Te Schichten . Zum Wachstum wurden sowohl die Substrattemperatur als auch die Ge, Sb und Te Flüsse variiert. Es wird gezeigt, dass die Komposition der Schicht stark von der Wachtumstemperatur abhängt und nur entlang der pseudibinären Verbindungslinie von GeTe-Sb2Te3 variiert. Zur Kontrolle des Wachstums wurde dabei die in-situ Quadrupol Massenspektroskopie verwendet. Es zeigen sich diverse inkommensurate Beugungsmaxima entlang der [111] Oberflächennormalen der Schichten, anhand derer die Ausbildung einer Lehrstellen Ordnung in Form einer Überstruktur diskutiert wird. / Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence x-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb2Te3 thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb2Te3 to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by x-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed.

The role of clusters in planetary atmospheres and the interstellar medium is potentially important. Investigating such a role requires basic experimental information, however lacking. The goal of this thesis was to develop an efficient experimental set-up to produce clusters in the laboratory in concentrations large enough to allow their high resolution spectra to be recorded, thus providing the necessary data allowing the physico-chemical properties of the clusters to be studied. The study of this subject however suffers from the lack of basic experimental data. The goal is therefore to produce clusters in the laboratory in concentration large enough to record their high resolution spectrum. This is the initial aim of the present thesis. During this work, we have built and extensively tested a new experimental set-up called FANTASIO (``Fourier trANsform, Tunable diode and quadrupole mAss spectrometers interfaced to a Supersonic expansIOn'). With the help of this new device, various experiments on jet-cooled species have been performed. The cartography of the supersonic expansion was established, using the mass spectrometer as a moving pressure probe. This enabled us to characterize the geometrical properties of the supersonic jet produced by circular and slit nozzles and to determine the position of the virtual nozzle. The effect of the axisymmetric expansion geometry on the R(0) lineshape in the nu_3 band of N_2O, recorded by FTIR, was also investigated. The rotational temperature of the jet-cooled molecules was determined to be a few K by measuring the intensity of lines in spectra recorded by FTIR spectroscopy. Vibrational energy transfer occuring in the expansion between N_2O molecules and different collision partners was investigated on the nu_2+nu_3-nu_2 band of N_2O, again using FTIR spectroscopy. The trend of these transfers was found to be related to the energy difference between the v_2=1 level of N_2O and the closest vibrational state in the collision partner, with the largest population. The sensitivity of the set-up was enhanced by a factor of 5 by increasing the absorption path length, using a multipass system. A procedure to remove the residual gas contribution from the IR spectra was developped, based on the mass spectrometer. Thanks to this sensitivity increase, broadband absorption features of clusters were observed for a C_2H_2-Ar mixture in circular and slit expansions. The optical sensitivity of FANTASIO was again increased by the implementation of the CW-CRDS system. The enhancement over FTIR was calculated to be over a factor 750. Thanks to this drastic improvement, spectral signatures of various clusters were recorded, such as C_2H_2-Ar, C_2H_2 multimers, C_2H_2-N_2O and C_2H_2-CO_2, at high resolution. The role of clustering in generating unusual line shapes of acetylene in an axisymmetric expansion was investigated. We demonstrated that C_2H_2 aggregates produced in the expansion are responsible for central dips observed in the monomer absorption. These acetylene clusters thus appear to be formed in the centre of the expansion, while, unexpectedly, acetylene-Ar complexes are formed at the edge of the conical expansion. Various research prospects were explored during this thesis thanks to the FANTASIO device, opening new research directions. FANTASIO is today operational and defines a useful tool to achieve the study of small clusters by infrared spectroscopy./ Le rôle des agrégats dans les atmosphères planétaires et dans le milieu interstellaire est potentiellement important. Cependant, les études sur ce sujet souffrent du manque de données expérimentales. Le but de cette thèse était de développer un dispositif expérimental efficace pour produire au laboratoire des agrégats en quantité suffisante pour permettre l'enregistrement de leur spectre infrarouge à haute résolution et donc l'étude de leurs propriétés physico-chimiques. Durant ce travail, nous avons construit et testé un nouveau dispositif expérimental appelé FANTASIO, basé sur un jet supersonique couplé à un spectromètre de masse, un spectromètre à transformée de Fourier et un système CRDS. Grâce à cet appareillage, différentes expériences sur des molécules à basse température ont été menées. L'expansion supersonique a été cartographiée en utilisant le spectromètre de masse comme une sonde de pression mobile. Cette cartographie nous a permis d'établir les propriétés géométriques des jets supersoniques produits par les orifices circulaire et de type fente, et de déterminer la position de l'orifice virtuel. L'effet de la géométrie de l'expansion sphérique sur le profil de la raie R(0) de la bande nu_3 de N_2O, enregistré par FTIR, a aussi été étudié. Une température rotationnelle de quelques K a été déterminée pour les molécules refroidies en jet supersonique par mesure de la distribution d'intensité de raies dans les spectres enregistrés par FTIR. Le transfert d'énergie vibrationnelle entre des molécules de N_2O et différents partenaires collisionnels a été étudié en analysant l'intensité de la bande nu_2+nu_3-nu_2 de N_2O, enregistré également par spectroscopie FTIR. Il a été trouvé que la tendance de ces transferts est liée à la différence d'énergie entre le niveau v_2=1 de N_2O et l'état vibrationnel le plus proche et le plus peuplé du partenaire collisionnel. La sensibilité du dispositif a été augmentée d'un facteur 5 dû à l'allongement du chemin d'absorption, grâce à l'utilisation d'un système multipassage. Une procédure basée sur l'utilisation du spectromètre de masse et visant à enlever la contribution du gaz chaud résiduel dans les spectres infrarouges a été mise au point. Grâce à cette augmentation de sensibilité, des structures d'absorption non résolues d'agrégats ont été observées dans des expansions en trou et en fente d'un mélange de C_2H_2-Ar. La sensibilité optique de FANTASIO a encore été augmentée par l'ajout au dispositif d'un système CW-CRDS. L'amélioration par rapport au spectromètre à transformée de Fourier a été calculée comme étant supérieure à un facteur 750. Grâce à cette importante amélioration, les signatures spectrales de divers agrégats, tels que C_2H_2-Ar, des multimères de C_2H_2, C_2H_2-N_2O et C_2H_2-CO_2, ont été enregistrées à haute résolution. Le rôle de l'agrégation dans la génération de profils de raie inhabituels dans une expansion en trou de l'acétylène a été étudié. Nous avons démontré que les agrégats de C_2H_2 produits dans le jet supersonique sont responsables des creux observés dans le profil d'absorption du monomère. Ces agrégats apparaissent donc comme étant formés au centre de l'expansion, tandis que, de manière inattendue, les agrégats de C_2H_2-Ar sont formés aux bords de l'expansion conique. Plusieurs idées de recherche ont été explorées durant cette thèse grâce au dispositif FANTASIO, ouvrant de nouvelles directions de recherche. FANTASIO est aujourd'hui opérationnel et se présente comme un outil utile dans l'étude des petits agrégats par spectroscopie infrarouge.

This thesis investigates the loss of high mass ions due to the initial thermal energy in ion trap mass analyzers. It provides an analytical expression for estimating the percentage loss of ions of a given mass at a particular temperature, in a trap operating with a set of conditions. The investigations have been carried out on quadrupole and cylindrical ion trap geometries. The three-dimensional Maxwellian velocity distribution function has been assumed to derive an expression for the percentage of ions lost. Adopting an approximation based on the observed escape velocity profiles of ions, an expression for the percentage loss of ions of a given mass has been derived as a function of the temperature for an ensemble of ions, its mass and its escape velocity. An analytical expression for the escape velocity has also been developed. It is seen that the escape velocity is a function of the trapping field, drive frequency and ion mass. Because the trapping field is determined by trap design parameters and operating conditions, it has been possible to study the influence of these parameters on ion loss. The parameters investigated include ion temperature, magnitude of the initial potential applied to the ring electrode (which determines the low mass cut-off), trap size, dimensions of apertures in the endcap electrodes and RF drive frequency. The studies demonstrate that ion loss due to initial thermal energy increases with increase in mass and that ion escape occurs in the radial direction. Reduction in the loss of high mass ions is favoured by lower ion temperatures, increasing low mass cut-off, increasing trap size, and higher RF drive frequencies. The dimensions of the apertures in the endcap electrodes do not influence ion loss in the range of aperture sizes considered.

Axially symmetric rf ion traps consists of a mass analyser having three electrodes, one of which is a central ring electrode and the other two are endcap electrodes. In the ideal Paul trap mass spectrometer, the electrodes have hyperboloidal shape (March and Hughes, 1989) and in mass analyser with simplified geometry, such as the cylindrical ion trap (Wu et al.,2005) the central electrode is a cylinder and the two endcap electrode and flat plates. rf-only or rf/dc potential is applied across the ring electrode and the grounded endcap electrodes for conducting the basic experiments of the mass spectrometer. In recent times, the miniaturisation of ion trap is one of the research interests in the field of mass spectrometry. The miniaturisation has the advantages of compactness, low power consumption and portability. However, this is achieved at the cost of the overall performance of the mass spectrometer with its deleterious effect on resolution. Research groups study the field distribution in the trap for better understanding of ion dynamics in the direction of achieving improved performance with the miniaturised traps. One aspect which has not received any attention in research associated with quadrupole ion traps is the possible role of the magnetic field in improving performance of these traps. Since in the quadrupole ion trap mass analyser ion is confined by an oscillating (rf) field, magnetic fields have been considered superfluous. The motivation of the thesis is to understand the dynamics of ions in axially symmetric rf ion traps, in the presence of the magnetic field. The axially symmetric rf ion trap geometries considered in this thesis are the Paul trap and the cylindrical ion trap (CIT). The changes incurred to the ion motion and Mathieu stability diagram in the presence of magnetic field is observed in this work. Also, the relation between the magnetic field and the Mathieu parameter is shown. The thesis contains 4 chapters: Chapter 1 provides the basic back ground of mass spectrometry and the operating principles. The equations of ion motion in the Paul trap is derived and also the solution to Mathieu equation is provided. The solution to the Mathieu equation are the Mathieu parameters and , when plotted with on the x-axis and on the y-axis, results in the Mathieu stability plot, the explanation of which is also given in the chapter. A brief description of the secular frequency associated with the ion dynamics is given in this chapter. The popular experiments conducted (i.e. the mass selective boundary ejection and resonance ejection) with a mass spectrometer is described here. Finally at the end of the chapter is the scope of the thesis. Chapter 2 facilitates with the preliminary study required fort he accomplishment of the task. The Paul trap and the CIT are the rf ion traps considered in this work. The geometries of these two traps are described in this chapter. The computational methods used for the analysis of various aspects of mass spectrometer is introduced. The computational methods used involve the methods used for calculating the charge distribution on the electrodes, potentials, multipole co-efficients and trajectory calculations. The boundary element method(BEM), calculation for Potentials and the Runge-Kutta method used for the trajectory calculations are introduced in this chapter. The expressions for calculating the multipole co-efficients are also specified. Chapter 3 presents the results obtained. The equations of ion motion in a quadrupole ion trap in the presence of magnetic field is derived here. Verification of numerical results with and without the magnetic field are presented at the end of this chapter. The chapter also presents various graphs showing the impact of magnetic field on the ion dynamics in the Paul trap and the CIT. The impact of the presence of magnetic field on the micro motion in -, -and -directions of the rf ion traps are shown in this chapter. Also the figures showing the variation in the Mathieu stability plots, with varying magnetic field intensity are presented in the chapter. At the end of this chapter the relation between the magnetic field and the Mathieu parameter is derived and plotted. Chapter 4 explains the various observations made from the results obtained. This chapter also highlights the future scope of the work for making this a more applicable one. References in the text have been given by quoting the author’s name and year of publication. Full references have been provide, in an alphabetic order, at the end of the thesis.

The most important substances of the group of perfluorinated compounds are perfluorooctyl sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorooctane sulphonamide (FOSA). Perfluorinated compounds have special physical and chemical properties, which make them valuable for usage in different industrial branches. These properties, which make them so useful are also the reason, why they are so harmful for the environment. The target of theoretical part of the diploma thesis was processing of literature searche on the topic: Evaluation of environmental load by perfluorinated compounds. In the experimental part was developed and optimized a method that was used for the identification and quantification of selected pollutants contained in real soil samples.

No description available.

Afin de préciser l'origine des volatils terrestres et les flux actuels et passés vers l’atmosphère, de nombreuses études s’intéressent à la composition du manteau. Ce réservoir est échantillonné naturellement lors des éruptions volcaniques, mais une grande partie des gaz est alors émise dans l'atmosphère, de sorte que la composition des volatils du manteau reste peu contrainte. Nous cherchons à préciser les mécanismes de dégazage sous les dorsales océaniques afin de corriger ces fractionnements. L'analyse (He-Ne-Ar-CO2) de verres basaltiques issus de la dorsale des Galápagos, dans la zone d'influence du point chaud des Galápagos, montre que la composition en volatils des laves s'explique par distillation de Rayleigh d'une source unique. Cette source est distincte de celle du point chaud (isotopes du néon), impliquant un dégazage en profondeur du panache ou une hétérogénéité spatiale de sa composition.Plusieurs verres volcaniques issus de la dorsale Atlantique et Est Pacifique ont été imagés par micro-tomographie aux rayons X. L'étude met en évidence des mécanismes de nucléation et de croissance des bulles différents sous les deux dorsales. De la convection en périphérie de la chambre magmatique avant l’éruption a été mise en évidence par l’étude pétrologique des verres. Les vésicules imagées ont ensuite été ouvertes individuellement sous vide par ablation laser et analysées (CO2, 4He, isotopes de l'argon). La composition des bulles est hétérogène dans certains échantillons et compatible avec une distillation de Rayleigh. Les tendances de dégazage obtenues permettent d'obtenir localement la composition de la source mantellique, qui est hétérogène.L'étude permet également d'appréhender l'hétérogénéité des rapports 40Ar/36Ar dans les chambres magmatiques par la technique d’ablation laser qui diminue la contamination atmosphérique par rapport à la technique classique de broyage / The composition of mantle volatiles is related to the origin of Earth's volatiles and to the past and present volatile fluxes to the atmosphere. Although this reservoir is naturally sampled during volcanic eruptions, most of the volatiles are lost to the atmosphere during this event, thus the composition of mantle volatiles is still uncertain. We try here to precise the processes of degassing below mid-oceanic ridges to correct the lava compositions for degassing.The He-Ne-Ar-CO2 analyses of basaltic glasses sampled along the Galapagos Spreading Center, in the area of influence of the Galapagos hotspot, show that the volatile composition of lavas is fully explained by a Rayleigh distillation of a unique source distinct from the plume source. These results imply that the plume degasses at depth or is heterogeneous.Several volcanic glasses from Mid-Atlantic ridge and East Pacific Rise have been imaged by X-rays microtomography. The mechanisms of vesicle nucleation and growth appear to be different below the two ridges. A step of convection at the magma body margin has been evidenced by the petrologic study of the glasses. Imaged vesicles have been subsequently opened under vacuum by laser ablation and analysed (CO2, 4He, argon isotopes). We observe, depending on the samples, either a single composition for all bubbles, or variations in composition between bubbles consistent with a trend of equilibrium degassing in an open system. The trends of degassing allow extrapolating locally to the volatile composition of the mantle source, which is heterogeneous. We also studied the heterogeneity of 40Ar/36Ar ratios in magmatic chambers using the laser opening method, which lowers the contribution of atmospheric gases compared to the classical crushing method

Atmospheric fine particulate matter (PM2.5), which is mostly formed in the atmosphere from precursor gases, contributes to numerous environmental and health concerns. Quantifying the ambient concentrations of PM2.5 and precursor gases can be challenging. Hence, many scientific questions about the formation, chemical composition, and gas/particle partitioning of PM2.5 remain unanswered. Ambient Ion Monitor - Ion Chromatography (AIM-IC) was characterized and utilized to measure the water-soluble composition of PM2.5 (dominated by pNH4+, pSO42-, and pNO3-) and associated precursor gases (dominated by NH3(g), SO2(g), and HNO3(g)) during two field campaigns. The AIM-IC detection limits for hourly sampling were determined to be 3 - 45 ng m-3. The response time for “sticky” gases was significantly improved with a nylon denuder membrane. A novel inlet configuration for the AIM-IC, which minimizes sampling inlet losses and carryover in sample analyses, was implemented. Measurements from the BAQS-Met 2007 campaign were utilized to assess the accuracy of the AURAMS model and investigate gas/particle partitioning in SW Ontario. Due to high sulphate levels, NH3(g) was the limiting chemical factor in the formation and gas/particle partitioning of PM2.5. The errors in the predictions of relative humidity and free ammonia were responsible for the poor agreement iii between modelled and measured pNO3- values. The AIM-IC measurements from the CalNex 2010 study were compared to the CMAQ model and utilized to investigate the gas/particle partitioning in Bakersfield, CA. Very high NH3(g) concentrations were observed, and the formation and partitioning of PM2.5 was limited by HNO3(g) and H2SO4. Evidence of rapid removal of HNO3(g) by interactions with super-micron dust particles, and possibly with the alkaline surface was found. CMAQ exhibited significant biases in the predicted concentrations of pSO42-, NH3(g) and HNO3(g).

Atmospheric fine particulate matter (PM2.5), which is mostly formed in the atmosphere from precursor gases, contributes to numerous environmental and health concerns. Quantifying the ambient concentrations of PM2.5 and precursor gases can be challenging. Hence, many scientific questions about the formation, chemical composition, and gas/particle partitioning of PM2.5 remain unanswered. Ambient Ion Monitor - Ion Chromatography (AIM-IC) was characterized and utilized to measure the water-soluble composition of PM2.5 (dominated by pNH4+, pSO42-, and pNO3-) and associated precursor gases (dominated by NH3(g), SO2(g), and HNO3(g)) during two field campaigns. The AIM-IC detection limits for hourly sampling were determined to be 3 - 45 ng m-3. The response time for “sticky” gases was significantly improved with a nylon denuder membrane. A novel inlet configuration for the AIM-IC, which minimizes sampling inlet losses and carryover in sample analyses, was implemented. Measurements from the BAQS-Met 2007 campaign were utilized to assess the accuracy of the AURAMS model and investigate gas/particle partitioning in SW Ontario. Due to high sulphate levels, NH3(g) was the limiting chemical factor in the formation and gas/particle partitioning of PM2.5. The errors in the predictions of relative humidity and free ammonia were responsible for the poor agreement iii between modelled and measured pNO3- values. The AIM-IC measurements from the CalNex 2010 study were compared to the CMAQ model and utilized to investigate the gas/particle partitioning in Bakersfield, CA. Very high NH3(g) concentrations were observed, and the formation and partitioning of PM2.5 was limited by HNO3(g) and H2SO4. Evidence of rapid removal of HNO3(g) by interactions with super-micron dust particles, and possibly with the alkaline surface was found. CMAQ exhibited significant biases in the predicted concentrations of pSO42-, NH3(g) and HNO3(g).