Thesis (M.E.)--University of Canterbury, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 159-166). Also available via the World Wide Web.

Not accounting for the electronic polarizability due to divalent ions such as Ca2+ introduces a significant artifacts to force field-based molecular dynamic simulations of biological systems. Two newly developed parameter refinements were used to compute the free energy profile of the Ca2+ -Cl- ion dissociation in aqueous solutions, to be compared with a free energy profile obtained from ab-intio molecular dynamics and to data from neutron scattering. Next, the computational evidence for the existence of a local free energy min- imum representing a guanidinium-guanidinium contact ion pair in aqueous solu- tions is provided suggesting a global preference for a contact ion pair. Finally, the passive membrane penetration mechanism of oligoarginines was investigated on a cell membrane model systems - lipid vesicles - by fluorescent spectroscopy. In this study, a mechanistic link between membrane penetration and vesicle aggregation and fusion was found. 1

Neste trabalho descreve-se o desenvolvimento de metodologias para análise de metais pesados em águas de abastecimento (sistema Guarapiranga) e em água de chuva por métodos voltamétricos, a quantificação de cátions e ânions por eletroforese capilar com detecção condutométrica sem contato (EC-DCC), a construção de eletrodos de prata a partir de CD-Rs e sua aplicação para medidas potenciométricas, amperométricas e voltamétricas, a confecção de microeletrodos de ouro explorando técnicas de micro-fabricação com toner e sua aplicação como detector amperométrico em eletroforese capilar e o uso de máscaras de toner para construção de redes de microeletrodos de ouro, platina e carbono. Para o desenvolvimento de metodologia para monitorar chumbo, cobre e mercúrio em águas de abastecimento e em água de chuva, enfatizou-se a utilização de dispositivos semidescartáveis de ouro construídos a partir de CD-Rs utilizando técnicas eletroanalíticas de redissolução. O limite de detecção para 300 s de pré-concentração foi calculado em 80, 90 e 100 ng L-1 para Pb2+, Cu2+ e Hg2+, respectivamente. O volume mínimo de amostra necessário para esta análise é de 0,5 mL. Para analisar estes metais em amostras de águas coletadas do sistema Guarapiranga, foi implementado um método alternativo simples e de baixo custo para eliminação da matéria orgânica presente nestas amostras. Este método permite o pré-tratamento de um grande número de amostras simultaneamente. Em adição à quantificação de metais pesados, ao longo deste trabalho também foi otimizada uma metodologia para o monitoramento de vários outros íons (Cl-, NO3-, SO42-, CH3COO-, F-, PO43-, NH4+, K+, Na+, Ca2+, Mg2+ e Li+) em águas do sistema Guarapiranga utilizando equipamento de eletroforese capilar com detecção condutométrica sem contato (EC-DCC) construído no laboratório. O limite de detecção para estes íons foi calculado em 0,23, 0,43, 0,50, 4,26, 0,75, 1,00, 0,09, 0,18, 0,19, 0,20, 0,19 e 0,23 mg L-1, respectivamente. Além da utilização de eletrodos de ouro, ao longo desta tese também foi desenvolvida metodologia para a construção de sensores a partir de CD-Rs de prata. São discutidas as diferentes etapas envolvidas na elaboração destes dispositivos, é apresentada a sua caracterização e são mostrados os resultados obtidos por voltametria de redissolução para análise de chumbo, por amperometria/FIA para análise de cianeto e por potenciometria/FIA para análise de cloreto. A aplicação de técnicas de micro-fabricação com toner para desenvolver detectores amperométricos de ouro para eletroforese capilar foi outro assunto estudado. Estes sensores foram acoplados a um sistema de eletroforese capilar utilizando uma célula do tipo \"wall-jet\". A potencialidade deste tipo de detecção em eletroforese capilar foi demonstrada com a análise simultânea de iodeto, ácido ascórbico, dipirona e paracetamol. O limite de detecção para estes íons foi calculado em 0,1, 0,5, 3,1 e 1,1 µmol L-1, respectivamente. O uso de máscaras de toner para construir redes de microeletrodos de ouro, platina e carbono é outro tópico apresentado nesta tese. Informações detalhadas sobre as etapas e parâmetros envolvidos na construção deste tipo de sensor são apresentadas. O desempenho, assim como algumas características peculiares destes dispositivos são demonstradas através do uso de sistemas químicos conhecidos e os resultados obtidos comparados com os de um eletrodo convencional. / This study describe the development of methodologies for the analysis of heavy metals in drinking water supply (Guarapiranga system) and in rain water by using voltammetric methods, for the quantification of cations and anions by capillary electrophoresis using contactless conductometric detection (CE-CCD), the construction of silver electrodes utilizing recordable CDs and its application for potentiometric, amperometric and voltammetric analysis, the confection of microelectrodes utilizing microfabrication techniques with toner and its application as electrochemical detector in capillary electrophoresis and the utilization of toner masks to construct gold, platinum and carbon microelectrodes arrays. In the development of methodologies for lead, copper and mercury monitoring for natural waters and in rain water, was emphasized the utilization of semi-disposable gold electrodes constructed from recordable CDs, utilizing stripping analysis techniques. The detection limit utilizing 300 s pre-concentration time was calculated as 80, 90 and 100 ng L-1 for Pb2+, Cu2+ e Hg2+, respectively. The minimum sample volume for each analysis is 0.5 mL. For the analysis of these metals in waters samples collected in the Guarapiranga dam, a simple and alternative low cost method to eliminate the organic mater present in these samples was implemented. This method permits the pre-treatment of many samples simultaneously. In addition to the quantification of heavy metals, in the course of this work, the methodology for monitoring many other ions (Cl-, NO3-, SO42-, CH3COO-, F-, PO43-, NH4+, K+, Na+, Ca2+, Mg2+ e Li+) in the waters from Guarapiranga dam utilizing capillary electrophoresis with contactless conductometric detection (CE-CCD), an instrument constructed in the laboratory was also optimized. The detection limit for these ions was calculated as 0.23, 0.43, 0.50, 4.26, 0.75, 1.00, 0.09, 0.18, 0.19, 0.20, 0.19 e 0.23 mg L-1, respectively. Apart from the utilization of gold electrodes, on this work, we also developed a new methodology for the construction of sensors starting from silver CD-Rs. The different steps involved in the manufacture of these devices are discussed, its characterization is presented and the results obtained utilizing voltammetry for lead analysis, FIA/amperometry for the analysis of cyanide and FIA/potentiometry for the analysis of chloride. The utilization of microfabrication techniques with toner to develop amperometric gold detectors for capillary electrophoresis applications was another subject investigated. These sensors were coupled a capillary electrophoresis system using a wall-jet type cell. The potentiality of this type of detection for capillary electrophoresis was demonstrated for the simultaneous analysis of iodide, ascorbic acid, dipyrone and paracetamol. The detection limit for these ions was calculated as 0.1, 0.5, 3.1 and 1.1 µmol L-1, respectively. The utilization of masks made with toner to construct arrays of gold, platinum and carbon microelectrodes is another topic presented in this thesis. Detailed information about the steps and factors involved in the construction of this kind of sensor are presented. The performance as well as some peculiar characteristics of these devices are demonstrated utilizing well know chemical systems and the results obtained compared to the ones of a conventional electrode.

Neste trabalho descreve-se o desenvolvimento de metodologias para análise de metais pesados em águas de abastecimento (sistema Guarapiranga) e em água de chuva por métodos voltamétricos, a quantificação de cátions e ânions por eletroforese capilar com detecção condutométrica sem contato (EC-DCC), a construção de eletrodos de prata a partir de CD-Rs e sua aplicação para medidas potenciométricas, amperométricas e voltamétricas, a confecção de microeletrodos de ouro explorando técnicas de micro-fabricação com toner e sua aplicação como detector amperométrico em eletroforese capilar e o uso de máscaras de toner para construção de redes de microeletrodos de ouro, platina e carbono. Para o desenvolvimento de metodologia para monitorar chumbo, cobre e mercúrio em águas de abastecimento e em água de chuva, enfatizou-se a utilização de dispositivos semidescartáveis de ouro construídos a partir de CD-Rs utilizando técnicas eletroanalíticas de redissolução. O limite de detecção para 300 s de pré-concentração foi calculado em 80, 90 e 100 ng L-1 para Pb2+, Cu2+ e Hg2+, respectivamente. O volume mínimo de amostra necessário para esta análise é de 0,5 mL. Para analisar estes metais em amostras de águas coletadas do sistema Guarapiranga, foi implementado um método alternativo simples e de baixo custo para eliminação da matéria orgânica presente nestas amostras. Este método permite o pré-tratamento de um grande número de amostras simultaneamente. Em adição à quantificação de metais pesados, ao longo deste trabalho também foi otimizada uma metodologia para o monitoramento de vários outros íons (Cl-, NO3-, SO42-, CH3COO-, F-, PO43-, NH4+, K+, Na+, Ca2+, Mg2+ e Li+) em águas do sistema Guarapiranga utilizando equipamento de eletroforese capilar com detecção condutométrica sem contato (EC-DCC) construído no laboratório. O limite de detecção para estes íons foi calculado em 0,23, 0,43, 0,50, 4,26, 0,75, 1,00, 0,09, 0,18, 0,19, 0,20, 0,19 e 0,23 mg L-1, respectivamente. Além da utilização de eletrodos de ouro, ao longo desta tese também foi desenvolvida metodologia para a construção de sensores a partir de CD-Rs de prata. São discutidas as diferentes etapas envolvidas na elaboração destes dispositivos, é apresentada a sua caracterização e são mostrados os resultados obtidos por voltametria de redissolução para análise de chumbo, por amperometria/FIA para análise de cianeto e por potenciometria/FIA para análise de cloreto. A aplicação de técnicas de micro-fabricação com toner para desenvolver detectores amperométricos de ouro para eletroforese capilar foi outro assunto estudado. Estes sensores foram acoplados a um sistema de eletroforese capilar utilizando uma célula do tipo \"wall-jet\". A potencialidade deste tipo de detecção em eletroforese capilar foi demonstrada com a análise simultânea de iodeto, ácido ascórbico, dipirona e paracetamol. O limite de detecção para estes íons foi calculado em 0,1, 0,5, 3,1 e 1,1 µmol L-1, respectivamente. O uso de máscaras de toner para construir redes de microeletrodos de ouro, platina e carbono é outro tópico apresentado nesta tese. Informações detalhadas sobre as etapas e parâmetros envolvidos na construção deste tipo de sensor são apresentadas. O desempenho, assim como algumas características peculiares destes dispositivos são demonstradas através do uso de sistemas químicos conhecidos e os resultados obtidos comparados com os de um eletrodo convencional. / This study describe the development of methodologies for the analysis of heavy metals in drinking water supply (Guarapiranga system) and in rain water by using voltammetric methods, for the quantification of cations and anions by capillary electrophoresis using contactless conductometric detection (CE-CCD), the construction of silver electrodes utilizing recordable CDs and its application for potentiometric, amperometric and voltammetric analysis, the confection of microelectrodes utilizing microfabrication techniques with toner and its application as electrochemical detector in capillary electrophoresis and the utilization of toner masks to construct gold, platinum and carbon microelectrodes arrays. In the development of methodologies for lead, copper and mercury monitoring for natural waters and in rain water, was emphasized the utilization of semi-disposable gold electrodes constructed from recordable CDs, utilizing stripping analysis techniques. The detection limit utilizing 300 s pre-concentration time was calculated as 80, 90 and 100 ng L-1 for Pb2+, Cu2+ e Hg2+, respectively. The minimum sample volume for each analysis is 0.5 mL. For the analysis of these metals in waters samples collected in the Guarapiranga dam, a simple and alternative low cost method to eliminate the organic mater present in these samples was implemented. This method permits the pre-treatment of many samples simultaneously. In addition to the quantification of heavy metals, in the course of this work, the methodology for monitoring many other ions (Cl-, NO3-, SO42-, CH3COO-, F-, PO43-, NH4+, K+, Na+, Ca2+, Mg2+ e Li+) in the waters from Guarapiranga dam utilizing capillary electrophoresis with contactless conductometric detection (CE-CCD), an instrument constructed in the laboratory was also optimized. The detection limit for these ions was calculated as 0.23, 0.43, 0.50, 4.26, 0.75, 1.00, 0.09, 0.18, 0.19, 0.20, 0.19 e 0.23 mg L-1, respectively. Apart from the utilization of gold electrodes, on this work, we also developed a new methodology for the construction of sensors starting from silver CD-Rs. The different steps involved in the manufacture of these devices are discussed, its characterization is presented and the results obtained utilizing voltammetry for lead analysis, FIA/amperometry for the analysis of cyanide and FIA/potentiometry for the analysis of chloride. The utilization of microfabrication techniques with toner to develop amperometric gold detectors for capillary electrophoresis applications was another subject investigated. These sensors were coupled a capillary electrophoresis system using a wall-jet type cell. The potentiality of this type of detection for capillary electrophoresis was demonstrated for the simultaneous analysis of iodide, ascorbic acid, dipyrone and paracetamol. The detection limit for these ions was calculated as 0.1, 0.5, 3.1 and 1.1 µmol L-1, respectively. The utilization of masks made with toner to construct arrays of gold, platinum and carbon microelectrodes is another topic presented in this thesis. Detailed information about the steps and factors involved in the construction of this kind of sensor are presented. The performance as well as some peculiar characteristics of these devices are demonstrated utilizing well know chemical systems and the results obtained compared to the ones of a conventional electrode.

The presence of inorganic ions is one of the criteria for thermal water assessing. The most important anions that affect the water quality and allow their use for therapeutic purposes, include sulfates, chlorides, nitrates and bicarbonates. Ions (as sodium, potassium, calcium and magnesium) are the significant cations. The ion chromatography is used for separation of these substances and also some methods based on electrophoretic migration of ions in an electric field. The electromigration method of isotachophoresis was chosen for determination of selected ions in water samples collected from thermal boreholes in Pasohlávky.

No description available.

Diffusion is a fundamental process which occurs in a wide variety of phases. It plays an important role in chemistry, physics, biology, materials science etc. In recent times, diffusion in confined systems has been widely investigated. Porous aluminosilicates such as zeolites, carbon nano tubes and metal organic frameworks(MOF) provide confined regions within which small molecules can diffuse. Indeed, diffusion within these materials have attracted considerable attention in the past few decades (see for example, “Diffusion in Zeolites and Other Microporous Solids”, J. Ka¨rger and D..M. Ruthven, John Wiley &Sons, NewYork,1992). Diffusion in confined spaces exhibits rich variety. For example, single file diffusion, window effect, levitation effect (LE), super-and sub-diffusive motion have all been observed in confined regions. Levitation effect provides an explanation for the dependence of self-diffusivity on the diameter of the diffusant. Consider a diffusant diffusing within a porous material. The pore network provided by the pore material may be characterized by the void and the neck distribution where the necks are the narrower regions interconnecting larger voids. It has been seen that diffusivity is maximum when the size of the diffusant is large and when it is comparable to the diameter of the bottleneck of the pore network. Recently it has been demonstrated that the levitation effect also exists in dense liquids such as water and dense solids. These developments essentially unify our understanding of diffusion in widely differing condensed matter phases. These results show that there is fundamentally no difference between porous substances and dense media at least with regard to dependence of self-diffusivity on the diameter of the diffusant. Chapter 1 provides a brief introduction to the subject of hydrocarbons confined within zeolites and ionic conductivity in polar solvents. We have given a description of the different applications of zeolites in the area of catalysis, separation etc. Window effect, single file diffusion, levitation effect and enhancement of viscosity of confined fluids are described. A brief review of various computational studies of hydrocarbons confined within zeolites is given. This is followed by a discussion of different experimental techniques and their use in the study of diffusion and adsorption within zeolites by many different groups in the last few decades. In the last section of the chapter we have discussed the anomalous size dependence of ionic conductivity in polar solvents which presumably has its origin in the Levitation Effect(LE). We have explained different theories proposed previously to understand the non-monotonic behavior of ionic conductivity as a function of ionic radius. A molecular dynamics(MD) investigation and quasi-elastic neutron scattering (QENS) study of pentane isomers in zeolite NaY is pre-sented in Chapter 2. QENS provides the first direct experimental evidence for LE. In an earlier study, a maximum in diffusivity as a function of the diameter of the diffusant for monatomic sorbates confined within zeolite NaY was observed by MD simulation. Since LE has been invoked to explain the diffusion in a wide variety of condensed matter phases, an experimental evidence of the levitation effect would be of great value. QENS measurements were carried out by Dr. Herve Jobic. Surprisingly we found that neopentane shows higher diffusivity than n-pentane and isopentane although its cross-sectional diameter perpendicular to the long molecular axis is larger compared to isopentane and n-pentane in agreement with predictions of LE. There is an excellent agreement between QENS results and MD simulation. LE predicts that the isomer with high diffusivity has low activation energy. The activation energies have been calculated from the Arrhenius plots using QENS as well as MD data. These follow the order Ea(n−pentane)>Ea(isopentane)>Ea(neopentane). Various other properties such as potential energy barrier at the bottleneck, velocity auto correlation function, intermediate scattering function, k dependence of the width of the dynamic structure factor have been computed. These provide additional insights into the nature of the motion of these isomers. They suggest that the barrier at the 12-ring window depends on the molecular diameter and levitation parameter of isomer. In Chapter 3, we report molecular dynamics simulation study of n-hexane and 2,2-dimethylbutane(DMB) mixture confined within the pores of zeolite NaY. We have taken an equimolar composition of the mixture consisting of n-hexane and DMB. The total number of hydrocarbon molecules in the system is 128. The simulations were carried out at various temperatures of 170, 200, 250 and 300 K. We have computed the self-diffusivities from the slope of the mean square displacement. It is found that the diffusivity of DMB is 0.82 ×10−9 m2/sec and that of n-hexaneis0.38 ×10−9 m2/sec. All previous studies of linear hydrocarbon and its branched analogue in different zeolites in the literature suggest that it is the linear member which has higher self-diffusivity. The cross-sectional diameter of DMB perpendicular to the long molecular axis is higher than that of n-hexane. Thus, DMB should have lower diffusivity. In order to understand this behavior of diffusivity we have computed the activation energies from the Arrhenius plots. The activation energy of DMB is found to be lower than that of n-hexane. This is inconformity with the levitation effect which states that the molecule with larger diameter comparable to that of the bottleneck diameter has low activation energy. We have also computed the potential energyprofileatthe12-ring window. The potential energy profile shows a barrier for n-hexane and a minimum for DMB at the window. This is in agreement with the previous results on monatomic species. We have computed other properties such as velocity auto correlation function, intermediate scattering function as well as wave number dependence of full width at half maximum of dynamic structure factor. These properties explain in detail the motion of n-hexane and DMB within NaY zeolite. In Chapter 4 molecular dynamics investigation into diffusion of n-decane and 3-methylpentane mixture within zeolite NaY. We have studied an equimolar mixture of n-decane and 3-methylpentane (36 of each) in the supercages of NaY zeolite in such a way that the con-centration is one molecule for every three cages. Simulations were performed at four different temperatures : 300, 350, 400 and 450 K. The distribution and orientation of the molecules inside the cage and at the window plane have been studied. Inside the cage, 3-methylpentane stays more close to the inner surface of the zeolite whereas n-decane prefers to stay close to the center of the cage. Both the species prefer to stay with their long molecular axis parallel to the surface of the zeolite. During passage through the window, 3-methylpentane is closer to the window center than n-decane. The distribution of the angle subtended by the end-to-end vector of the molecule with the normal to the window plane, while the molecular center is in the window plane, shows that 3-methylpentane samples a larger range of orientation than n-decane. This may lead to an entropic barrierfor n-decane. We have computed the diffusivity of both the molecules. Diffusivity of 3-methylpentane is found to be higher than n-decane. This behavior is consistent with the observations made in the last two chapters. The activation energy of 3-methylpentane is found to be 3.17 kJ/mol and forn-decaneitis6.0kJ/mol. This agrees with the prediction of levitation effect. The energy profile a the window shows shallow minimum for both n-decane and 3-methylpentane. Therefore, the energy profile does not describe the nature of motion of the molecules. We have computed the the dihedral angle distribution when the molecule is at the adsorption site and when it is at the window plane. The distributions essentially remain same for 3-methylpentane whereas a considerable change in the distributions is seen for n-decane. The gauche population of n-decane increases at the cost of trans population when it goes from the adsorption site to the window. The lower diffusivity of n-decane can be partly attributed to the change in the dihedral angle. Also, the orientational entropic barrier may be another cause of the slow motion of n-decane. Thus, in the present study the slow motion of n-decane is partly explained by levitation effect and partly by the change in the dihedral angle as well as the entropic barrier. Overall, the results in the last three chapters leads to the main conclusion that the branched isomer will diffuse faster than a linear hydrocarbon in zeolites with 12-ring window such as zeolite NaY. In Chapter 5, diffusion of pentane isomers in zeolites NaX and NaY has been investigated using pulsed field gradient nuclear magnetic resonance(PFG-NMR) and molecular dynamics(MD) techniques respectively. Temperature as well as concentration dependence of diffusivity have been studied. The diffusivities obtained from NMR are roughly an order of magnitude smaller than those obtained from MD. The dependence of diffusivity on loading at high temperatures exhibits a type I behavior according to the classification of K¨arge rand Pfeifer. NMR diffusivities of the isomers exhibit the order D(n−pentane)>D(isopentane)>D(neopentane). The results from MD are in agreement with the QENS results where the diffusivities of the isomers follow the order D(n-pentane)<D(isopentane)<D(neopentane). The activation energies from NMR show Ea(n-pentane)<Ea(isopentane) <Ea(neopentane) whereas those from MD suggest the order Ea(n-pentane) >Ea(isopentane) >Ea(neopentane). The latter follows the predictions of levitation effect whereas those of NMR appears to be due to the presence of defects in the zeolite crystals. The differences between NMR and MD are attributed to the long time and length scales over which NMR samples are probed compared to MD or QENS. Th eresults from these studies suggests that although branched isomer intrinsically have higher diffusivities than linear hydrocarbons in zeolites such as NaY, the presence of defects can effectively annul this higher diffusivity of the branched isomer. Correlation of self-diffusivity and entropy of monatomic sorbates con-fined within zeolite NaY has been investigated in Chapter 6. We have carried out molecular dynamics simulation on monatomic sor-bates within zeolite NaY at 150, 110 and 90 K. As suggested by the Levitation Effect, the self-diffusivity shows a non-monotonic behavior as a function of the diameter of the sorbates. We have computed the entropy of the sorbates of various sizes ranging from 3.07˚ A to 7.0˚ A using the method proposed by Goddard and his co-workers as well as from the radial distribution function. The variation of entropy with the diffusant diameter exhibits a behavior similar to that of the self-diffusivity on diffusant diameter, thereby showing a strong correlation between the entropy and diffusivity. The loss of entropy on adsorption is a minimum for the diffusant with maximum diffu-sivity. This is in agreement with the experimental measurements of Kemball. Thus, entropy follows the prediction of the levitation effect. With decrease in temperature both self-diffusivity as well as entropy show more pronounced maximum as a function of the diameter of the sorbate. The dimensionless diffusivity from three different isotherms follow a Rosenfeld type of excess entropy scaling rule, D∗= Aexp(αSe) where A and α are the scaling coefficients. In Chapter 7 we have investigated the self-diffusivity as well as cor-rected diffusivity of pure methane in faujasite NaY combining quasi elastic neutron scattering experiment and molecular dynamics simu-lation. The QENS experiment carried out at 200 K led to an unex-pected dependence of self-diffusivity on loading for pure methane with the presence of a maximum at 32 CH4/unit cell. This is at variance with previous reports. Typically, diffusivity of a polar species such as methane in a zeolite such as NaY exhibits a monotonic decrease with loading. Molecular dynamics simulation was performed to reproduce this experimentally observed behavior. We could reproduce the diffusivity behavior qualitatively with a maximum at 16 CH4/unit cell. The corrected diffusivities obtained from both experiment as well simulation show similar behavior as the self-diffusivity with maximum at an intermediate loading. The experimental behavior was reproduced only when the interaction of methane with the sodium cation is in-creased suggesting that this interaction may be important. In Chapter8 we have investigated the role of attractive interaction on size dependent diffusivity maximum of ions in water. We have per-formed molecular dynamics simulation of mode lions in water. Earlier study of systems interacting only through van der Waals interaction shows that the size dependent diffusivity maximum or the levitation effect disappears when the attractive term(r−6 term) of the Lennard-Jones potential is put equal to zero. It is not clear whether the absence of the dispersion interaction in a system where there is electrostatic attraction will lead to a size dependent diffusivity maximum. There-fore, two sets of simulations with and without dispersion interaction between the ion and water have been carried out at700Kinorderto understand the influence of the attractive interaction. It is found that the self-diffusivity of the ions indeed exhibits an anomalous maximum as a function of the vanderWaals diameter for both the sets, viz., with dispersion and without dispersion interaction. In fact, the diffusivity maximum is seen to be more pronounced when there is no dispersion interaction. This existence of the maximum in self diffusivity when there is no dispersion interaction between the ion and the water is attributed to the attractive term from electrostatic interactions. De-tailed analysis shows that the solvent shell is more well defined in the presence of dispersion interactions. The velocity auto correlation function shows undulation at short times for the smaller ions indicating rattling motion inside the cage formed by the surrounding water molecules. Smaller ion exhibits a bi-exponential decay while a single exponential decay is seen for the ion with maximum diffusivity in the intermediate scattering function. The solvent structure appears to determine much of the dynamics of the ion. Interesting trends are seen in the activation energies and these can be understood in terms of the Levitation Effect.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-10-24T12:57:59Z No. of bitstreams: 1 PATRICIA_DISSETAÇÃO_MESTRADO_GEOQUIMICA_2009.pdf: 4047978 bytes, checksum: b2a1f62ef245a5a0d8afcc3ae828bf17 (MD5) / Made available in DSpace on 2017-10-24T12:57:59Z (GMT). No. of bitstreams: 1 PATRICIA_DISSETAÇÃO_MESTRADO_GEOQUIMICA_2009.pdf: 4047978 bytes, checksum: b2a1f62ef245a5a0d8afcc3ae828bf17 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A cidade de São José dos Campos localizada no Vale do Paraíba é considerada uma área altamente suscetível à poluição do ar devido à geografia desta região, caracterizada por cadeias montanhosas que dão origem a Serra do Mar e Mantiqueira, dificultando a circulação geral da atmosfera e comprometendo a dispersão de poluentes atmosféricos bem como às emissões industriais de alto potencial poluidor proveniente dos parques industriais existente na região e suas vizinhanças. O objetivo do trabalho é caracterizar o material particulado atmosférico fino (PM2,5) e grosso (PM2,5-10) e determinar a composição química dos constituintes inorgânicos solúveis em água associados a estas partículas. As amostras de PM2,5 e PM2,5-10 foram coletadas semanalmente, em período contínuo de 24 h, por intermédio de um amostrador Dicotômico PM10 Sierra-Andersen em São José dos Campos entre fevereiro de 2004 a fevereiro de 2005 totalizando 60 amostragens. As concentrações médias anuais ± desvio padrão de PM2,5 e PM2,5-10 foram respectivamente iguais a 15,7 ± 7,9 e 14,8 ± 8,4 μg m-3. As maiores concentrações de particulado fino e grosso ocorreram no período de estiagem, enquanto que as concentrações mais baixas no período de chuvas, evidenciando o papel fundamental das chuvas na limpeza da atmosfera . Os íons NH4 + e SO4 2- ocorreram predominantemente no particulado fino correspondendo a 62% do total dos constituintes e 20 % da massa; por outro lado, os íons Cl-, Na+ e NO3 - predominaram no particulado grosso equivalendo, juntos, a 54 % dos íons inorgânicos e 11% da massa. Em média, 96% do SO4 2- associado ao PM2,5 equivale ao excesso de SO4 2-, ou seja, a outras fontes naturais e/ou antrópicas não provenientes do sal do mar. A razão NH4 +/ (Exc-SO4 2- + NO3 -) encontrada no PM2,5 igual a 1,08 sugere a formação de aerossóis de (NH4)2SO4 e NH4NO3 provenientes de atividades antrópicas. O déficit médio de cloreto foi de 42% para o PM2,5 e de 39% para o PM2,5-10. O déficit de Cl- para o PM2,5 durante o período de estiagem foi 4 vezes maior do que no período de chuvas, sendo o mesmo não observado para o PM2,5-10. Mais de 90% do K+, Ca2+ e Mg2+ encontrados em ambas as frações finas e grossas representa a parcela não-marinha (natural e/ou antrópica) destes íons. A modelagem hysplit para as retrotrajetórias de massas de ar auxiliou na identificação de episódios de transporte a longa distância, de material particulado de procedência continental e marítima em amostras que apresentaram composição química extremamente alta. A distribuição de chuvas ao longo do período de estudo, foi fundamental para o entendimento do comportamento sazonal das partículas atmosféricas finas e grossas em São José dos Campos. / São José dos Campos, located in the Paraíba Valley, is an area considered highly susceptible to air pollution because of its geography, characterized by mountain ranges that result in Serra do Mar and Mantiqueira, disturbing the general circulation of the atmosphere and threatening the dispersion of air pollutants as well as the high pollution potential emissions from industrial parks that exist in the region and in neighborhood. The objective of this study is to characterize the atmospheric fine (PM2,5) and coarse particulate (PM2,5-10) matter and determine the chemical composition of water-soluble inorganic constituents of these particles. The samples of PM2,5 and PM2,5-10 were weekly collected, in a continuous period of 24 hours with a PM10 dichotomic Sierra-Andersen sampler in São José dos Campos between February 2004 and February 2005, totalizing 60 samples. The annual average concentrations ± standard deviation of PM2,5 and PM2,5-10 were, respectively, 15,7 ± 7,9 and 14,8 ± 8,4 μg m-3. The highest concentrations of fine and coarse particulate matter occurred in the period of drought while lower concentrations were found in rainy period, highlighting the fundamental role of rain in cleaning the atmosphere. NH4 + and SO4 2- ions occurred predominantly in fine particulate matter corresponding to 62% of all constituents and 20% of the mass, on the other hand, Cl-, Na+ and NO3 - ions predominated in coarse particulate matter together amounting 54% of inorganic ions and 11% of the mass. On average 96% of the SO4 2- associated with PM 2,5 equal the Exc-SO4 2-, i.e. other natural and/or anthropic sources not from saltwater. The reason NH4 + / (Exc-SO4 2- + NO3 -) found in PM2,5 equals 1.08 suggesting the formation of (NH4)2SO4 and NH4NO3 aerosols from human activities. The average deficit of chloride was 42% for PM2,5 and 39% for PM2,5-10. The deficit of Cl- for PM2,5 during the drought period was 4 times higher than the one found in the rainy period, the same was not observed for PM 2,5-10. Over 90% of K+, Ca2+ and Mg2+ found in both fine and coarse fractions represent the non-marine parcel (natural and/or antropic) of those ions. The modeling hysplit for air masses retrotrajectories helped identifying long-distance transport episodes, particulate matter of continental and marine origin in samples that showed extremely high chemical composition. The distribution of the rain throughout the study was fundamental for understanding the seasonal behavior of atmospheric fine and coarse particles in Sao Jose dos Campos.