Esta dissertação investiga o registro de conteúdo iônico do testemunho de gelo monte Johns (79°55'28"S; 94°23'18"O) obtido na Antártica Ocidental, contribuindo para o adensamento espacial de informações glacioquímicas empregadas em estudos paleoclimáticos. As concentrações de Na+ (16,6 ± 28,2 μg L-1), K+ (1,3 ± 3,7 μg L-1), Mg2+ (3,7 ± 3,7 μg L-1), Ca2+ (5,4 ± 3,4 μg L-1), Cl- (33,3 ± 43,7 μg L-1), SO42- (25,9 ± 17,7 μg L-1), NO3- (50,8 ± 18,5 μg L-1) e H3CSO3- (7,1 ± 5,4 μg L-1) foram determinadas por cromatografia iônica em 2.164 amostras para o período 1882–2008. A variabilidade sazonal de NO3- e, especialmente do nssSO42-, em antifase com Na+, possibilitou a datação pela contagem de ciclos anuais ao longo do período estudado. A identificação dos sinais vulcânicos do Krakatoa (1883), Agung (1963) e Pinatubo/Hudson (1991) foi usada para determinar horizontes de referência (datação absoluta). Eventos de aporte significativo de aerossóis foram identificados e agrupados considerando o conteúdo iônico, proveniência e estação do ano. A avaliação da proveniência dos íons e do balanço iônico mostra a origem da carga iônica: 36% é oriunda de aerossóis de sal marinho, 13% de poeira mineral, 17% de atividade biogênica marinha e 34% de produtos da reatividade química na atmosfera. É observada uma leve redução nas concentrações de Mg2+ (-0,04 μg L-1 ano-1) e K+ (-0,01 μg L-1 ano-1), e mais forte para NO3- (-0,17 μg L-1 ano-1), no período 1909–2008. A média anual da acumulação líquida de neve foi 0,21 ± 0,04 m eq. H2O no período 1882–2008 sem apresentar tendência significante. A acumulação mostra alta correspondência com dados anuais de reanálise climática, com coeficiente de correlação cruzada de +0,42 (α < 0,05) para o período 1979–2008. / This dissertation investigates the ionic content record of the mount Johns ice core (79°55'28"S; 94°23'18"W) recovered from the West Antarctica, contributing to the spatial densification of glaciochemical information used in paleoclimatic studies. The concentrations of Na+ (16.6 ± 28.2 μg L-1), K+ (1.3 ± 3.7 μg L-1), Mg2+ (3.7 ± 3.7 μg L-1), Ca2+ (5.4 ± 3.4 μg L-1), Cl- (33.3 ± 43.7 μg L-1), SO42- (25.9 ± 17.7 μg L-1), NO3- (50.8 ± 18.5 μg L-1) e H3CSO3- (7.1 ± 5.4 μg L-1) were determined by ion chromatography on 2,164 samples for the period 1882–2008. The NO3- seasonal variability and, especially, of the nssSO42- in antiphase with the Na+, allowed the counting of annual cycles over the studied period. The identification of Krakatau (1883), Agung (1963) and Pinatubo / Hudson (1991) volcanic signals was used to determine reference horizons (absolute dating). Significant aerosols events were identified and grouped considering the ionic content, provenance and season of the year. The evaluation of the ions provenance and of the ionic balance points to ionic content origin: 36% come from sea salt aerosols, 13% from mineral dust, 17% originate from marine biogenic activity and 34% are chemical reactivity products in the atmosphere. It is observed a slight reduction in the Mg2+ (-0.04 μg L-1 y-1) and K+ (-0.01 μg L-1 y-1) concentrations, and stronger in the NO3- (-0.17 μg L-1 y-1), during the 1909–2008 period. The annual mean net accumulation rate averaged 0.21 ± 0.04 m w.e. y-1 in the period 1882–2008 did not show any significant trend and shows high correspondence with climatic reanalysis data in years with data overlap, with a cross-correlation coefficient of +0.42 (α < 0.05) for the period 1979–2008.

Per- and polyfluoroalkyl substances (PFASs) are synthetic chemicals which are used in a wide range of applications such as aqueous film forming foam (AFFF) for firefighting, paint, coating and cosmetics. For almost a decade, PFASs have received worldwide attention because of the ubiquitous detection of PFAS in the environment and their bioaccumulative, persistent and give toxic effects on animals and humans. A number of study have shown many unknown organofluorine present in environmental samples. The total oxidizable precursor (TOP) method is an oxidation method to convert any precursor compounds of PFASs into measurable perfluorinated carboxylic acids (PFCAs) or sulfonic acids (PFSAs). The aims of this project are to evaluate if the use of total oxidizable precursor (TOP) assay may help improve the mass balance analysis between the quantifiable PFASs and extractable organofluorine in samples. In this study, three water samples: landfill leachate water, contaminated groundwater and adiluted Sthamex AFFF with tap water were undergone TOP assay to reveal the present of any unidentified precursor compounds. To obtain the extractable organofluorine and quantifiable PFAS levels in the samples, combustion ion chromatography (CIC) and liquid chromatography – tandem mass spectrometry (LC-MS/MS) were used, respectively. Results suggested the presence of unidentified precursor compounds in the samples with the aid of TOP assay reaction. Although after the oxidative conversion, a large portion of unidentified PFASs compounds were still present in the samples. The quantifiable PFASs in the samples were up to 7 % of the EOF; in other word, there were still around 93 % of unidentified compounds present in the samples. Further development of analytical method for characterization or identification of these unknown PFAS compounds is needed.

Esta dissertação investiga o registro de conteúdo iônico do testemunho de gelo monte Johns (79°55'28"S; 94°23'18"O) obtido na Antártica Ocidental, contribuindo para o adensamento espacial de informações glacioquímicas empregadas em estudos paleoclimáticos. As concentrações de Na+ (16,6 ± 28,2 μg L-1), K+ (1,3 ± 3,7 μg L-1), Mg2+ (3,7 ± 3,7 μg L-1), Ca2+ (5,4 ± 3,4 μg L-1), Cl- (33,3 ± 43,7 μg L-1), SO42- (25,9 ± 17,7 μg L-1), NO3- (50,8 ± 18,5 μg L-1) e H3CSO3- (7,1 ± 5,4 μg L-1) foram determinadas por cromatografia iônica em 2.164 amostras para o período 1882–2008. A variabilidade sazonal de NO3- e, especialmente do nssSO42-, em antifase com Na+, possibilitou a datação pela contagem de ciclos anuais ao longo do período estudado. A identificação dos sinais vulcânicos do Krakatoa (1883), Agung (1963) e Pinatubo/Hudson (1991) foi usada para determinar horizontes de referência (datação absoluta). Eventos de aporte significativo de aerossóis foram identificados e agrupados considerando o conteúdo iônico, proveniência e estação do ano. A avaliação da proveniência dos íons e do balanço iônico mostra a origem da carga iônica: 36% é oriunda de aerossóis de sal marinho, 13% de poeira mineral, 17% de atividade biogênica marinha e 34% de produtos da reatividade química na atmosfera. É observada uma leve redução nas concentrações de Mg2+ (-0,04 μg L-1 ano-1) e K+ (-0,01 μg L-1 ano-1), e mais forte para NO3- (-0,17 μg L-1 ano-1), no período 1909–2008. A média anual da acumulação líquida de neve foi 0,21 ± 0,04 m eq. H2O no período 1882–2008 sem apresentar tendência significante. A acumulação mostra alta correspondência com dados anuais de reanálise climática, com coeficiente de correlação cruzada de +0,42 (α < 0,05) para o período 1979–2008. / This dissertation investigates the ionic content record of the mount Johns ice core (79°55'28"S; 94°23'18"W) recovered from the West Antarctica, contributing to the spatial densification of glaciochemical information used in paleoclimatic studies. The concentrations of Na+ (16.6 ± 28.2 μg L-1), K+ (1.3 ± 3.7 μg L-1), Mg2+ (3.7 ± 3.7 μg L-1), Ca2+ (5.4 ± 3.4 μg L-1), Cl- (33.3 ± 43.7 μg L-1), SO42- (25.9 ± 17.7 μg L-1), NO3- (50.8 ± 18.5 μg L-1) e H3CSO3- (7.1 ± 5.4 μg L-1) were determined by ion chromatography on 2,164 samples for the period 1882–2008. The NO3- seasonal variability and, especially, of the nssSO42- in antiphase with the Na+, allowed the counting of annual cycles over the studied period. The identification of Krakatau (1883), Agung (1963) and Pinatubo / Hudson (1991) volcanic signals was used to determine reference horizons (absolute dating). Significant aerosols events were identified and grouped considering the ionic content, provenance and season of the year. The evaluation of the ions provenance and of the ionic balance points to ionic content origin: 36% come from sea salt aerosols, 13% from mineral dust, 17% originate from marine biogenic activity and 34% are chemical reactivity products in the atmosphere. It is observed a slight reduction in the Mg2+ (-0.04 μg L-1 y-1) and K+ (-0.01 μg L-1 y-1) concentrations, and stronger in the NO3- (-0.17 μg L-1 y-1), during the 1909–2008 period. The annual mean net accumulation rate averaged 0.21 ± 0.04 m w.e. y-1 in the period 1882–2008 did not show any significant trend and shows high correspondence with climatic reanalysis data in years with data overlap, with a cross-correlation coefficient of +0.42 (α < 0.05) for the period 1979–2008.

Actuellement, 80 à 85% des cuirs sont tannés au chrome. Ce procédé permet d'obtenir d'excellentes propriétés physico-mécaniques dans des conditions économiques optimales. Les sels de chrome sous forme trivalente utilisés lors de la fabrication du cuir ne sont pas nocifs; cependant sous certaines conditions et associés à d'autres substances, le chrome trivalent peut se transformer en chrome hexavalent, très allergisant et pouvant s'avérer dangereux pour la santé du consommateur. Depuis le 1er mai 2015, la présence de chrome hexavalent dans le cuir est soumise à la législation européenne; la teneur en chrome hexavalent ne doit pas excéder plus de 3 mg/kg de poids sec total du cuir (REACh ANNEXE 17, §47). A ce jour, de nombreux travaux de recherche ont été réalisés et des premières hypothèses ont été avancées pour expliquer la formation du chrome hexavalent dans le cuir. L'objectif de ce projet de recherche a été de rationaliser et d'approfondir ces différentes études pour essayer de mieux appréhender cette problématique. Ce projet de thèse a permis d'améliorer la spécificité et la fiabilité la méthode d'analyse pour la détermination de la teneur en chrome hexavalent en introduisant la chromatographie ionique. Ensuite, l'influence de la composition du cuir (matière grasse, indice d'iode, pH, chrome total et chrome extractible) sur la formation de chrome hexavalent dans le cuir a été étudiée afin d'expliquer l'origine et d'éventuels mécanismes d'oxydation du chrome trivalent (en chrome hexavalent). Enfin, cette étude s'est intéressée aux facteurs environnementaux (température, humidité relative, lumière et durée d'exposition), aux conditions de fabrication du cuir ou encore au cycle de vie du cuir (transport, transformation en produit fini, utilisation par le consommateur) afin de déterminer l'impact de ces paramètres sur la formation du chrome hexavalent. A l'issue de ce travail, une méthode de vieillissement "artificiel" représentative de l'évolution réelle d'un cuir a été proposée, et ce quelles que soient les caractéristiques et la nature du cuir / Currently, 80 to 85% of leather is tanned with chrome. This process allows to obtain excellent physico-mechanical properties with optimum economic conditions. The chromium salts in trivalent form used in the manufacturing of leather are not harmful; however under some conditions and associated with other substances, trivalent chromium can be transformed into hexavalent chromium, highly allergenic and potentially harmful to the health of the consumer. Since 1st May 2015, the presence of hexavalent chromium in leather is subject to European legislation; the hexavalent chromium content must not exceed 3 mg/kg of the total dry weight of leather (REACh ANNEX 17, § 47). To date, a great amount of research has been done and initial hypothesis have been able to explain the formation of hexavalent chromium in leather. The objective of this research project was to rationalize and to deal with these various studies in order to understand this problem in more detail. In this thesis project, the introduction of ion chromatography has improved the specificity and reliability of the analysis method for the determination of hexavalent chromium. Secondly, the influence of leather composition (fat liquor, iodine value, pH, total chromium and extractible chromium) on the formation of hexavalent chromium in leather was studied. The objective was to explain the potential oxidation mechanisms of trivalent chromium (in hexavalent chromium). The third part of this study deals with environmental factors (temperature, relative humidity, light and duration of exposure), leather manufacturing conditions or the life cycle of leather (transport, transformation into finished product, consumer use). The aim was to determine the impact of these parameters on the formation of hexavalent chromium. To conclude, an "artificial" ageing method representing the natural evolution of leather, and which corresponds to the characteristics and the nature of the leather, has been proposed

Fluoride, the most abundant form of fluorine, is an ion released into the environment, mainly via anthropogenic sources and erosion of mineral rocks. Although the element is well known for its health benefits on teeth and bones, it can as well be a harmful pollutant. In some areas on earth, the population can not obtain drinking water that is below the guideline limits of fluoride, which is set to 1.5 mg/L by the world health organization (WHO). Therefore there is a relevance to develop methods that can clean the waters from excess fluoride. The potential problems when it comes to finding these types of methods is that they can be expensive. However, materials generated as residues in industrial processes may be low in cost. In this thesis, silicon reduced AOD-slag, a material generated as a by-product from the production of stainless steel, was examined by its fluoride adsorption behavior and adsorption capacity. The concentrations of fluoride were measured with ion chromatography (IC) and the concentration of metals were analyzed with microwave plasma atomic emission spectroscopy (MP-AES). Additionally pH and conductivity were measured. The functionality of the material surface was analyzed with isotherm modeling, where the Sips isotherm model was tested. Moreover, optimization of the slag was performed by heat treating the material, as well as a sorption kinetics test on both optimized and original slags. The results from the analysis indicated that the material corresponds well to the Sips isotherm. Considering this result it is suggested that at low concentrations, the surface can be characterized as heterogeneous, with different binding energies at different available sites. At higher concentrations the Sips-model explains the surface to be saturated when a monolayer of fluoride is formed. Therefore the binding on the slag surface can be described to have an inner-sphere and covalent character. The metal analysis showed that calcium ions are released from the slag when in aqueous solutions. The presence of calcium in the liquid samples are believed to result in formations of solid calcium fluoride (CaF2), precipitated on the slag surface. Lastly, the maximum fluoride removal is believed to differ between different types of AOD-slag, where there as well are possibilities to optimize the material.

Per- and polyfluoroalkyl substances (PFAS) have been manufactured and used in differentapplications for several decades, including food packaging materials. During the last 20 yearsthese compounds have been acknowledged as hazardous for humans and the environment, anddifferent regulations on PFAS have been established on both national and international levels.Companies started to phase-out long-chain PFAS, including both PFOA and PFOS, around 20years ago. Since PFAS are persistent, this cause concerns both for our health and theenvironment, as well as possible PFAS contamination in new products due to the recycling ofmaterials. The aim of this study was to find an effective method to extract PFAS from differentfood packaging materials; analyze the samples for their extractable organofluorine (EOF)content using combustion ion chromatography; as well as analyze targeted PFAS in the samplesusing ultra-high performance liquid chromatography tandem mass spectrometry. The findingsof this study suggest that none of the selected samples had EOF contents above the Danishindicator value of 20 mg/kg dw TOF set to determine whether PFAS has been intentionallyadded to a material, and that only two samples exceeded the limit of detection for EOF. Atakeaway bowl made out of 100% sugarcane contained the highest EOF content while the outerpackaging of a cereal box contained the second highest EOF. Both PFOA and PFOS, alongwith other long-chain PFAS were detected in a majority of the samples. The lowest total PFASconcentrations when analyzing for targeted PFAS was detected in the sugarcane take awaybowl. The highest total PFAS concentration was detected in an egg carton, followed by theouter packaging of a cereal box (same as above) and the outer box of a waffle mix. The targetedPFAS was detected in almost all samples, with PFNA and 6:2 diPAP being the most frequentlydetected PFAS. PFCAs, PFSAs, FTSAs, FOSAAs and PAPs were detected in a majority of thesamples. The highest concentrations were measured for diSAmPAP in a majority of thesamples. Mass balance calculations of the sugarcane bowl showed that the targeted PFAS onlyaccounted for 0.04% of the extractable organofluorine content. In conclusion, none of thesamples displayed EOF contents higher than the Danish indicator value, suggesting that noneof the samples were intentionally treated with PFAS. However, targeted PFAS analysis of thesesamples showed that they still contain PFAS, that could be further recycled along with therecycling of paper and board food packaging materials. Considering the persistence of PFASand that these compounds can remain in the recycling chain, with the risk of also being releasedinto the environment, it is of importance that PFAS is not introduced in any of the stages in apaper or board containers life cycle.

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No description available.

Résumé : La pollution de l'environnement est devenue un problème mondial majeur. Le développement rapide des industries de procédés conduit à une augmentation constante des quantités d'eaux usées et des liqueurs contaminées rejetées. Les acides carboxyliques représentent une part importante de la charge organique des polluants dans les eaux usées et dans les solutions aqueuses industrielles. Une technologie efficace et respectueuse de l'environnement est donc requise pour réduire les effets négatifs de l'industrialisation sur l'environnement et pour éliminer les polluants des eaux usées et des liqueurs industrielles contaminées. Le plasma thermique submergé à courant continu (CC) est l'une des technologies proposées pour éliminer les contaminants des liquides et des solutions. Le réacteur au plasma thermique submergé à courant continu est un nouveau réacteur dans lequel le contact direct entre le plasma et la solution est établi. Une caractéristique importante du plasma thermique type CC est le gaz de plasma. Selon le type du gaz plasmagène, les plasmas thermiques CC présentent différents taux de décomposition, d’espèces réactives, d’enthalpies, de conductivités thermiques, et de temps de vie des électrodes. Parmi les différentes torches des plasmas thermiques CC, la torche à plasma thermique à mélange gazeux à base de CO[indice inférieur 2], récemment inventée, présente une amélioration très significative de la performance, c'est-à-dire une enthalpie plasmatique et une conductivité thermique élevées par rapport à celles des gaz de plasma concurrents. Une approche principalement expérimentale a permis d’étudier la faisabilité et le mécanisme de décomposition de l'acide carboxylique à haut poids moléculaire dans des solutions via les différents plasmas thermique submergés à CC. L'acide sébacique, un acide carboxylique à haut poids moléculaire a été choisi comme représentant de contaminant de type organique dans la liqueur Bayer. Deux différentes torches de plasma, incluant la torche à plasma oxygène et air ainsi que la torche à plasma CO[indice inférieur 2]/CH[indice inférieur 4] nouvellement conçues ont été utilisées. L'effet des différentes conditions de fonctionnement en incluant le temps de traitement, le pH initial de la solution, et la pression du réacteur, ainsi que le rôle des agents oxydants tels que le H[indice inférieur 2]O[indice inférieur 2], ont été étudiés sur la décomposition de l'acide sébacique. Pour identifier le rôle des différents gaz de plasma et des conditions opérationnelles sur le mécanisme de décomposition et sur les produits intermédiaires, une caractérisation qualitative et quantitative a été réalisée sur les solutions traitées avec la méthode de chromatographie ionique couplée à la spectrométrie de masse (IC/MS). L'effet thermochimique des gaz de plasma sur la décomposition de l’acide sébacique et sur les produits intermédiaires a également été étudié. À travers les différents essais réalisés dans cette étude, il a été montré pour la première fois que la décomposition de l'acide carboxylique de poids moléculaire élevé est réalisable avec le plasma thermique submergé en utilisant des gaz de plasmas différents. Le taux de décomposition d'acide sébacique lors de l’utilisation d’un plasma thermique à oxygène en milieu basique est plus élevé par rapport aux autres plasmas thermiques (air, et CO[indice inférieur 2]/CH[indice inférieur 4]) en mode submergé. Il a été constaté que cela est dû principalement à sa forte concentration en espèces oxydantes telles que l’ozone. Il a été observé que la décomposition de l'acide sébacique en milieu basique par l’utilisation de plasma d’oxygène et de plasma à air se produit par un mécanisme d'oxydation consécutif jusqu'à la production finale d'acides di-carboxyliques de plus faibles poids moléculaires et de CO[indice inférieur 2] (dissous dans la solution sous la forme de carbone inorganique). Il a été trouvé aussi pour la première fois que le plasma thermique submergé CO[indice inférieur 2]/CH[indice inférieur 4], peut décomposer l'acide carboxylique de poids moléculaire élevé sur la base d’un mécanisme séquentiel de photo-oxydation en raison de sa forte intensité de rayonnement ultraviolet. Le plasma de CO[indice inférieur 2]/CH[indice inférieur 4] a montré une vitesse de décomposition supérieure dans le milieu neutre. Par contre, en milieu basique, le plasma d'oxygène et le plasma d'air ont montré une vitesse de décomposition plus élevée. Il a également été montré que l'ajout d'H[indice inférieur 2]O[indice inférieur 2] en milieu basique a augmenté la vitesse de décomposition de l'acide sébacique avec le plasma CO[indice inférieur 2]/CH[indice inférieur 4] jusqu’à la même vitesse de décomposition que le plasma d'oxygène dû à une plus grande intensité de rayonnement UV du plasma de CO[indice inférieur 2] en comparaison avec celle du plasma d'oxygène. Dans une perspective plus générale, à travers différentes expériences, il a été montré que le plasma de CO[indice inférieur 2]/CH[indice inférieur 4] peut offrir une grande vitesse de décomposition des acides carboxyliques de poids moléculaire élevés dans un milieu acide et neutre, et également en milieu basique en présence de peroxyde d'hydrogène. Cela permettra le traitement des contaminants dans une grande variété de conditions de solution à l'aide de plasma du gaz CO[indice inférieur 2]. Les résultats de cette thèse aident à mieux comprendre la décomposition des contaminants organiques à hauts poids moléculaires dans les solutions utilisant les plasmas thermiques submergés. De plus, ces résultats proposent une application potentielle pour la torche à plasma de CO[indice inférieur 2] pour le traitement des eaux usées. // Abstract : Environmental pollution has become a major global problem. Rapid development of process industries leads to a constant increase in amounts of wastewater and contaminated industrial process liquors. Carboxylic acids represent a significant portion of the organic load of pollutant in wastewater and industrial aqueous solutions. An effective and environmentally friendly technology is therefore required to reduce the negative effects of industrialization on the environment and subsequently remove pollutants from wastewater and contaminated industrial liquors. DC (Direct Current) submerged thermal plasma is one of the proposed technologies for removing contaminants from liquids and solutions. DC submerged thermal plasma reactor is a novel reactor in which the direct contact between plasma and solution is established. An important characteristic of typical DC thermal plasma is the plasma gas. Depending on the type of plasma gas, DC thermal plasmas present different decomposition rates, reactive species, enthalpy, thermal conductivity, and electrode life time. Among different DC thermal plasma torches, the recently invented CO[subscript 2]-based gas mixture thermal plasma torch exhibits a very significant performance improvement, i.e. high plasma enthalpy and high thermal conductivity in comparison with competing plasma gases. In this study, by a mainly experimental approach, the feasibility and decomposition mechanism of high molecular weight carboxylic acid in solution via different DC submerged thermal plasmas has been investigated. Sebacic acid, a high molecular weight carboxylic acid, was selected as a representative of a typical organic contaminant in Bayer liquor. Two different DC plasma torches have been used including oxygen DC plasma torch and the newly designed CO[subscript 2]/CH[subscript 4] plasma torch. The effect of different operational conditions including treatment time, initial solution pH, and the reactor pressure as well as the role of oxidizing agents such as H[subscript 2]O[subscript 2], were investigated on the decomposition of sebacic acid. To identify the role of different plasma gases and operational conditions on the decomposition mechanism and its intermediate products, qualitative and quantitative characterization was done on the treated solutions with IC/MS (Ion Chromatography/Mass Spectrometry) method. The thermochemical effect of the plasma gases on the decomposition of sebacic acid and its intermediate products was also investigated. Through different experiments, it was shown for the first time that decomposition of high molecular weight carboxylic acid is feasible with submerged thermal plasma by using different plasma gases. The decomposition rate of sebacic acid by using oxygen thermal plasma in basic medium was higher compared with other thermal plasmas (air, and CO[subscript 2]/CH[subscript 4]) in submerged mode. It was found that the higher decomposition rate with oxygen plasma is mostly due to its high concentration of oxidant species such as ozone. The decomposition of sebacic acid in basic medium with oxygen and air plasma was revealed to occur with a consecutive oxidation mechanism up to the final production of the lowest molecular weight di-carboxylic acids and CO[subscript 2] gas (dissolved in solution in the form of inorganic carbon). It was found for the first time that the CO[subscript 2]/CH[subscript 4] submerged thermal plasma can decompose well high molecular weight carboxylic acid based on a sequential photo-oxidation mechanism due to its high ultraviolet (UV) radiation intensity. The CO[subscript 2]/CH[subscript 4] plasma showed higher decomposition rate in neutral medium, however oxygen and air plasma showed higher increased the sebacic acid decomposition rate with the CO[subscript 2]/CH[subscript 4] plasma up to the same decomposition rate of the oxygen plasma due to higher UV radiation intensity of the CO[subscript 2] plasma than that of the oxygen plasma. In a more general perspective, through different experiments, it was shown that CO[subscript 2]/CH[subscript 4] plasma can offer high decomposition rate for high molecular weight carboxylic acids in acidic and neutral medium and also in basic medium in the presence of hydrogen peroxide. This will allow using plasma for treatment of contaminants in a wide variety of solution conditions by using CO[subscript 2] gas. The findings of this thesis therefore will shed light on the decomposition of large organic contaminants in solutions with submerged thermal plasmas. Also, it provides a potential application for CO[subscript 2] plasma torch in wastewater treatment.

O objetivo deste estudo clínico foi comparar a influência do tipo de material e da estrutura física de dois fios dentais em liberar pirofosfato tetrassódico, no espaço interdental. Este estudo crossover foi conduzido em uma população de 10 indivíduos (ambos os sexos) com faixa etária variando entre 18 e 30 anos. Os sujeitos da pesquisa foram alocados aleatoriamente em uma das seguintes seqüências de uso dos fios dentais: (AB ou BA), onde A = polipropileno entrelaçado e B = nylon texturizado de acordo com o material e a estrutura com que os fios dentais foram produzidos. Cada indivíduo usou uma única vez, perfazendo 6 passadas por área-alvo (sendo definido como área alvo as duas faces interproximais dos dentes contíguos selecionados, ou seja, 3 passadas em cada face) cada fio da seqüência a ele alocada. Antes do uso do primeiro fio dental, assim como entre a permuta de fios, foi realizado um washout de uma semana sem fazer uso de qualquer produto que contivesse o princípio ativo (sal anti-tártaro). O fluido gengival das áreas-alvo foi colhido no espaço interdental, com cones de papel absorventes esterilizados (calibre # 35), nos seguintes tempos: (00) antes, (0) logo após; 1, 2, 4, (1, 2 e 4) horas após o uso de cada fio dental. A presença de pirofosfato nas amostras foi verificada por meio de cromatógrafo de íons IC 2000 (coluna AS-11 e pré-coluna AG-11). Os teores de pirofosfato foram comparados entre os dois tipos de fios dentais e entre os tempos de colheita das amostras. O pirofosfato tetrassódico foi detectado no fluido gengival de ambos os grupos em 95% das amostras no tempo 0 - imediatamente após o uso, em 45% das amostras no tempo 1 - após uma hora do uso e em 10% das amostras após 2 horas do uso. Após 4 horas do uso, em nenhuma das amostras foi detectada a presença do princípio ativo em níveis terapêuticos. Conclui-se que a composição do material e a estrutura física dos fios dentais não exerceram influência na liberação e na permanência do agente anti-tártaro, que permaneceu em níveis terapêuticos por um período de até 2 horas após o uso único. / The aim of this investigation was to compare the influence of the type of material and the physical structure of two antitartar dental flosses in releasing tetrasodium pyrophosphate in the interdental space. This crossover study involved 10 subjects (both genders) with ages ranging from 18-30 years old. The individuals were randomly assigned to one of the following sequences of use of the dental flosses (AB or BA), where A = tangled polypropylene and B = texturized nylon according to the structures and the materials what the dental flosses were made, forming two groups of five individuals each. Each individual used the floss 6 times in the target areas (defined as both interproximal surfaces of the selected teeth, 3 times in each surface). Before the use of the first dental floss and between the employments of the two flosses, a one week washout period was done without the use of products containing tetrasodium pyrophosphate. The gingival crevicular fluid of the target areas was sampled with sterile paper points (tapering # 35) in the following times: (00) before the use of the dental floss, (0) soon after the use; 1, 2, 4, (1, 2 and 4 hours after the use, respectively). The pyrophosphate contents in the samples were verified using an ion chromatograph IC 2000 (column AS-11 e pre-column AG-11). The contents of pyrophosphate were compared between the two flosses and among the sample collection times. Pyrophosphate was detected in the gingival crevicular fluid of both groups in 95% of the samples soon after their use, 45% after 1h and 10% after 2h of the use. After 4h, none of the samples had pyrophosphate at detectable levels. Both dental flosses released tetrasodium pyrophosphate at therapeutic levels for up to 2 hours after flossing. Based in the results it can be concluded that the material composition and the physical structure of the flosses had no influence in releasing the antitartar agent, which remained in therapeutic levels for a 2 hours period after the single use.