Dans un contexte de réchauffement climatique, une compréhension des mécanismes atmosphériques influençant le bilan radiatif terrestre est nécessaire. Les nuages peuvent participer à un refroidissement mais des incertitudes demeurent sur ces systèmes qui sont encore mal connus (notamment la composition de leur fraction organique). Depuis toujours, seules les réactions chimiques et surtout celles radicalaires sont considérées comme importantes pour jouer sur la composition des nuages. Cependant la découverte de microorganismes métaboliquement actifs pose la question de leur rôle en tant que biocatalyseurs. Ces microorganismes sont en effet à même d'utiliser des molécules carbonées comme nutriments, de dégrader des molécules précurseur des radicaux (H2O2) et de se prémunir contre le stress oxydant. L'objectif de ce travail est de mesurer l'impact des processus photochimiques et biologiques sur la composition chimique du nuage. Pour cela, la quantification de •OH, le radical responsable de la réactivité diurne, et l’évaluation de l’impact des microorganismes sur cette concentration à l’état stationnaire ont été entreprises. Après un développement en milieu modèle, la méthode a été appliquée à des eaux atmosphériques (eaux de pluies et eaux de nuages). Les concentrations obtenues sont de l'ordre de 10-17 à 10-15 M et ne sont pas modifiées en présence de microorganismes. Ces concentrations sont plus faibles que celles obtenues dans les modèles de chimie atmosphérique, ceci peut s’expliquer par un manque de connaissance sur la matière organique. Pour mieux caractériser cette dernière, des composés aromatiques simples présents dans des eaux de nuages ont été identifiés, le phénol a été retrouvé dans les 8 échantillons analysés. Une étude approfondie sur sa dégradation a donc été entreprise. Nous avons montré que des transcrits d’enzymes intervenant dans sa biotransformation sont synthétisés par les bactéries in situ dans l’eau de nuage. De plus, 93% des souches bactériennes testées, isolées de ce milieu, dégradent le phénol. Pour évaluer l'impact relatif des processus de dégradation biotique et abiotique du phénol, une expérience de photobiodégradation avec une souche modèle (Rhodococcus erythropolis PDD-23b-28) a été entreprise. Ces deux processus interviennent avec une importance de même ordre de grandeur. Ces résultats suggèrent que les microorganismes et les radicaux interviennent dans la remédiation naturelle de l'atmosphère. / In the context of global warming, more precise knowledge of atmospheric processes is needed to evaluate their impact on the Earth radiative budget. Clouds can limit the increase of temperature but this retroaction is not well understood due to a lack of knowledge of cloud media (like organic fraction composition). From the beginning of atmospheric studies, only chemical, especially radical, reactions was taken into account. However microorganisms metabolically active were found in cloud water arising questions about their role as biocatalyst. They are able to use carboxylic acids as nutriments, to degrade radical precursor (like H2O2) and to survive oxidative stress. The aim of this work is to quantify the impact of photochemical and biological processes on cloud chemistry composition. First, the concentrations of •OH, the most reactive radical, were evaluated and the influence of microorganisms on the concentrations were studied. A new method was developed in artificial medial before direct quantification of steady state •OH concentration in atmospheric waters (rain and cloud waters). Concentrations ranged from 10-17 to 10-15 M and did not change in presence of microorganisms. These measures were lower than concentrations estimated by chemical atmospheric models. A possible explanation was an underestimation of the main sink of this radical (organic matter). To better characterize this fraction, simple aromatic compounds were identified in cloud waters, phenol was found in the 8 samples analyzed. To go further, we studied phenol degradation in detail. Enzyme transcripts involved in phenol degradation were present in cloud water samples showing in situ activity of native bacteria. 93% of tested cultural strains, isolated from cloud waters, were able to degrade phenol. To quantify the relative contribution of radical versus microbial processes allowing phenol degradation, we performed photo-biodegradation experiment with a model strain (Rhodococcus erythropolis PDD-23b-28). Our results showed that these two processes participated equally to phenol degradation, suggesting that microorganisms and radicals can be involved in atmospheric natural remediation.

A reação de Fenton é o nome dado à oxidação de ferro(II) a ferro(III) pela água oxigenada, uma reação que produz espécies com alto poder oxidante como o radical hidroxila. Neste trabalho, foi desenvolvida uma metodologia espectrofotométrica para o acompanhamento da formação de ferro(III) nos momentos iniciais da reação de Fenton. Esta metodologia foi aplicada a quatro conjuntos de reações: (A) o sistema Fenton simples, contendo apenas ferro(II) e H2O2; (B) o sistema A contendo isopropanol, um substrato orgânico simples que sofre principalmente oxidação a acetona; (C) o sistema A contendo o catalisador 3,5-di-terc-butil-catecol (H2DTBCat); (D) o sistema C mais isopropanol, que corresponde ao sistema catalítico completo. Em cada conjunto, variou-se as concentrações de ferro(II) e H2O2. Um modelo cinético, baseado num conjunto de reações explícitas e as respectivas constantes de velocidade, foi desenvolvido para simular a velocidade de formação de ferro(III) para estes quatro conjuntos de reações. Utilizando reações relatadas na literatura, o modelo forneceu simulações que reproduziram satisfatoriamente os dados experimentais dos conjuntos A e B. No caso dos conjuntos C e D, porém, foi necessário propor uma etapa envolvendo a formação de ferro(IV) ou ferril, estabilizado por complexação com o H2DTBCat. Entretanto, mesmo com a inclusão desta espécie, o modelo não captou a complexidade do sistema em altas concentrações de peróxido e ferro. Esta falha foi atribuída à rápida degradação competitiva do H2DTBCat nestas condições, com a subseqüente participação destes produtos de degradação na reação ou como co-catalisadores ou como inibidores. / The Fenton reaction is the name given to the oxidation of iron(II) to iron(III) by hydrogen peroxide, a reaction that produces highly oxidizing species like the hydroxyl radical. In this work, a spectrophotometric methodology is developed to accompany the formation of iron(III) during the initial moments of the Fenton reaction. This methodology was applied to four sets of reactions: (A) the simple Fenton system, containing only iron(II) and H2O2; (B) system A containing isopropanol, a simple substrate that undergoes principally oxidation to acetone; (C) system A containing the catalyst 3,5-di-tert-butyl-catechol (H2DTBCat); (D) system C plus isopropanol, corresponding to the complete catalytic system. For each set of reactions, the concentrations of iron(II) and H2O2 were varied. A kinetic model, based on explicit chemical reactions and their respective rate constants, was developed to simulate the the rate of formation of iron(III) for these four sets of reactions above. Using reactions described in the literature, the model produced simulations that satisfactorily reproduced the experimental data of sets A and B. In the case of sets C and D, however, it was necessary to propose an additional step involving the formation of iron(IV) or ferril, stabilized by complexation with H2DTBCat. Nonetheless, even with the inclusion of this species, the model failed to capture the complexity of the system at high concentrations of peroxide and iron. This failure was attributed to the rapid competitive degradation of H2DTBCat under these conditions, with the subsequent participation of the degradation products in the reaction as either co-catalysts or inhibitors.

Ce sujet entre dans le cadre de l'étude d'un procédé d'oxydation avancé innovant dans le domaine de la dépollution des eaux, à savoir l'ionisation par faisceau d'électrons. Le radical hydroxyle (•OH) et l'électron hydraté (e−aq) sont les deux espèces majoritaires issues de l'ionisation de solutions aqueuses par un faisceau d'électrons d'intense énergie. Il a été démontré que la génération des radicaux supplémentaires tels que le radical sulfate (SO4•−) et le radical hydroxyle par les réactions radicalaires entre l'ion persulfate, le peroxyde d'hydrogène et l'électron hydraté respectivement, améliore l'efficacité de ce procédé pour la dégradation de polluants organiques en solution aqueuse. Dans le présent travail, la dégradation et la minéralisation de benzènesulfonate et naphthalènesulfonate de sodium, et d'acide gallique ont été obtenues par irradiation par faisceau d'électrons seul et couplé avec un oxydant (S2O8−−, H2O2). En absence d'oxydant une dose absorbée de 1,5 kGy a été suffisante pour l'élimination totale de ces composés. La présence d'oxydant permet généralement de réduire les doses d'irradiation nécessaires. Par ailleurs, l'augmentation de la concentration en oxydant ou de la dose appliquée a un effet bénéfique vis-à-vis de l'élimination du carbone organique. Cependant, le couplage S2O8−−/faisceau d'électrons est plus adapté que le couplage H2O2/faisceau d'électrons même en présence de constituants inorganiques. Les résultats obtenus soulignent l'importance du rôle du dioxygène dissous lors de l'étape de la minéralisation en vue de favoriser la formation des radicaux organiques (ROO•). Pour chaque une des molécules étudiées, des sous-produits d'oxydation... / This research belongs to the study of the ionization of aqueous solutions by electron beam (E.B.) as an advanced oxidation process for water treatment. The hydroxyl radical (•OH) and hydrated electron(eaq¯) are the two major active species produced from the ionization of aqueous solutions by high energy electron beam. It has been shown that the generation of additional radicals such as the sulphate radical (SO4•¯) and hydroxyl radical from the reaction of persulfate ion (S2O8¯) or hydrogen peroxide (H2O2) with the hydrated electron, improved the efficiency of this process towards the degradation and mineralization of organic pollutants in aquaeous solution. In the présent work, the degradation and mineralization of naphthalenesulfonate, benzenesulfonate and gallic acid were studied by electron beam irradiation alone and coupled with oxidants (S2O8¯, H2O2).In the absence of oxidant, an absorbed dose of 1,5 kGy leads to total elimnation of these pollutants. The presence of added oxidants usually reduces the radiation dose required. In addition, increasing oxidant concentration or applied dose had a beneficial effect towards the organic carbon removal. It was found that coupling E.B./S2O8¯ has more suitable than E.B./ H2O2 even in the presence of inorganic constituents. The results also highlighted the importance of dissolved oxygen in the system when mineralization is aimed. For each of the molecules studied, oxidation by-products resulting from hydroxylation and aromatic ring opening were identified.

The occurrences of cyanotoxin and organic contaminants threaten drinking water sources and are a serious human health and environmental concern. The control of these problematic contaminants and the remediation of the associated contaminants are critical for ensuring safe drinking water to significant populations. Advanced oxidation processes (AOPs) have received considerable attention as a potential water treatment for various pollutants. In this dissertation, advanced oxidative degradation of four problematic water toxic contaminants (CYN, iopamidol, 4-methylcyclohexane methanol and propylene glycol phenyl ether) were studied to develop the fundamental understanding required to assess AOPs as a potential water treatment process. UV and visible light activated (VLA) TiO2 photocatalysis using nitrogen and fluorine-TiO2 (NF-TiO2), phosphorus and fluorine-TiO2 (PF-TiO2) and sulfur-TiO2 (S-TiO2) were employed for degradation of 6-hydroxymethyl uracil (6-HOMU), a model compound for the potent cyanotoxin cylindrospermopsin (CYN). NF-TiO2 exhibits the most photoactive, followed by marginally active PF-TiO2 and inactive S-TiO2 under visible light irradiation. Our results indicate that O2-• plays an important role in VLA TiO2 photocatalysis. Fe (VI), an environmentally friendly oxidant, was employed for the degradation of CYN and 6-HOMU over a range of pH (7 ~ 9.5). The second order rate constants for the reaction of Fe (VI) with CYN decrease from 38.83 ± 0.07 M-1s-1 at pH 7 to 5.02 ± 0.04 M-1s-1 at pH 9.5. Fe (VI) mediated reactions primarily occur via oxidation of the uracil ring in CYN. ELISA results demonstrate that Fe (VI) oxidation process leads to a significant decrease in the bioactivity of CYN as a function of treatment time. Fe (III)-oxalate/H2O2 process was employed for the remediation of iopamidol, a model for ICM, to determine the formation rates and steady concentrations of •OH and O2-• under UV and visible light irradiation. Reduction by CO2-• and oxidation by •OH contribute to the degradation pathways. Pulse and gamma radiolysis of 4-methylcyclohexane methanol (MCHM) and propylene glycol phenyl ether (PPh) were studied to determine the bimolecular rate constants and reaction pathways. •OH addition to ortho and para positions in PPh are the predominant reaction pathways; H-abstraction are the primary reaction mechanisms for ∙OH mediated oxidation of MCHM

Cette thèse présente le devenir atmosphérique de trois alcools saturés CH3(CH2)4OH, CH3CH2CH2CH(OH)CH3 et (C2H5)2CHOH, de trois esters CH3CH2CH2C(O)OC2H5, CH3CH2C(O)OC2H5 et CH3CH2C(O)OCH2CH2CH3 ainsi que d’un HFC insaturé (CF3)2C=CH2 avec OH et Cl. La constante de vitesse de la réaction avec OH de ces composés a été déterminée en fonction de la température (253 – 373 K), en utilisant la technique Photolyse Laser Pulsée couplée à la Fluorescence Induite par Laser (PLP-FIL). La constante de vitesse de la réaction de OH et de Cl avec les alcools, les esters et l’hexafluoroisobutène (HFIB) a été également déterminée à température ambiante en utilisant la chambre de simulation atmosphérique. Pour la réaction du radical OH avec le HFC et de l’atome Cl avec les esters et le HFC, il s’agit d’une première détermination des constantes de vitesse. Les constantes de vitesse obtenues sont comparées à la littérature, la réactivité des alcools et des esters a été discutée. Enfin, le calcul des durées de vie de ces composés ainsi que la recherche de leurs produits éventuels ont permis d’évaluer l’impact atmosphérique de ces composés sur l’environnement. / In this thesis we report the atmospheric fate of three saturated alcohols: CH3(CH2)4OH, CH3CH2CH2CH(OH)CH3 and (C2H5)2CHOH, three esters: CH3CH2CH2C(O)OC2H5, CH3CH2COOC2H5 and CH3CH2COOCH2CH2CH3 and an unsaturated HFC with OH radicals and Cl atoms. The rate coefficients of OH reactions with these compounds have been measured over the temperature range 253 – 373 K, using the Pulsed Laser Photolysis – Laser Induced Fluorescence technique (PLP-LIF). Moreover the rate coefficients of OH and Cl reactions with alcohols, esters and hexafluoroisobutene (HFIB) have been determined at room temperature, using smog chambers. For the reaction of OH radicals with HFIB and Cl atoms with esters and HFIB, the rate coefficients obtained in this study present the first determination. The results have been compared with the literature and the reactivity of the compounds has been discussed. Finally, the atmospheric lifetimes of these compounds have been determined and the OH oxidation products have been identified, which allows us to estimate the atmospheric impact of these compounds.

No description available.

Dans cette étude, un nouveau complexe de fer est utilisé dans des processus d’oxydation avancée pour la dégradation de polluants organiques présents dans l’eau. Le fer ferrique (Fe(III)) et l’acide éthylène diamine-N,N’-disuccinique (EDDS) forment un complexe Fe(III)-EDDS dont la structure a été mise en évidence durant ce travail. Les propriétés photochimiques du complexe ont ensuite été évaluées en fonction de différents paramètres physico-chimiques dont le pH qui est apparu comme un paramètre clé pour l’efficacité des processus testés. Ensuite nous avons donc travaillé sur l’utilisation de ce complexe dans les processus de Fenton modifié, photo-Fenton et comme activateur des persulfates (S2O82-). Nos expériences ont été réalisées en présence du 4-tert-butylphénol (4-t-BP) qui est connu pour être un perturbateur endocrinien. Nous avons ensuite mis en évidence les conditions optimales du traitement pour la dégradation du 4-t-BP. Il est apparu que le pH joue un rôle très important et qu’en présence de ce complexe de fer, l’efficacité est plus importante pour des pH neutre ou légèrement basique. L’identification des radicaux oxydants responsables de la dégradation du polluant a également été réalisée. Dans ce cadre nous avons montré que le radical sulfate joue un rôle plus important que le radical hydroxyle lors du processus d’activation des persulfates. / Advanced Oxidation Processes (AOPs) have been proved to be successfully applied in the treatment of sewage. It can decolorize the wastewater, reduce the toxicity of pollutants, convert the pollutants to be a biodegradable by-product and achieve the completed mineralization of the organic pollutants. The Fenton technologies which are performed by iron-activated hydrogen peroxide (H2O2) to produce hydroxyl radical (HO•) has been widely investigated in the past few decades. Recently, Sulfate radical (SO4•-) which was produced by the activation of persulfate (S2O82-) is applied to the degradation of organic pollutants in water and soil. It is a new technology recently developed. It is also believed to be one of the most promising advanced oxidation technologies.In this study, a new iron complex is introduced to the traditional Fenton reaction. The ferric iron (Fe(III)) and Ethylene diamine-N,N′-disuccinic acid (EDDS) formed the complex named Fe(III)-EDDS. It can overcome the main disadvantage of traditional Fenton technology, which is the fact that traditional Fenton technology can only perform high efficiency in acidic condition. Simultaneously, EDDS is biodegradable and it is one of the best environment-friendly complexing agents. On the other hand, the transition metal is able to activate S2O82- to generate SO4•-. Therefore, Fe(III)-EDDS will also be applied to activate S2O82- in the present study. 4-tert-Butylphenol (4-t-BP) has been chosen as a target pollutant in this study. It is widely used as a chemical raw material and is classified as endocrine disrupting chemicals due to the estrogenic effects. The 4-t-BP degradation rate (R4-t-BP) is used to indicate the efficiency of the advanced oxidation processes which are based on Fe(III)-EDDS utilization. The main contents and conclusions of this research are shown as follows:In the first part, the chemical structure and properties of Fe(III)-EDDS and the 4-t-BP degradation efficiency in UV/Fe(III)-EDDS system were studied. The results showed that Fe(III)-EDDS was a stable complex which was formed by the Fe(III) and EDDS with the molar ratio 1:1. From the photoredox process of Fe(III)-EDDS, the formation of hydroxyl radical was confirmed including that HO• is the main species responsible for the degradation of 4-t-BP in aqueous solution. Ferrous ion (Fe(II)) was also formed during the reaction. With the increasing Fe(III)-EDDS concentration, 4-t-BP degradation rate increased but is inhibited when the Fe(III)-EDDS concentration was too high. Indeed, Fe(III)-EDDS is the scavenger of HO•. pH value had a significant effect on the degradation efficiency of 4-t-BP that was enhanced under neutral or alkaline conditions. On the one hand, Fe(III)-EDDS presented in the FeL-, Fe(OH)L2-, Fe(OH)2L3-, Fe(OH)4- four different forms under different pH conditions and they had different sensitivity to the UV light. On the other hand, pH value affected the cycle between Fe(III) and Fe(II ). The formation of hydroperoxy radicals (HO2•) and superoxide radical anions (O2•-) (pka = 4.88) as a function of pH was also one of the reasons. It was observed that O2 was an important parameter affecting the efficiency of this process. This effect of O2 is mainly due to its important role during the oxidation of the first radical formed on the pollutant. (...)

Cette thèse s’inscrit dans une volonté d’améliorer la compréhension des mécanismes fondamentaux de radiolyse de biomolécules par des ions accélérés, à l’échelle moléculaire. Ainsi, les ions étudiés ont été de différentes nature (H+, He2+, C6+) et de différentes énergies, correspondant à une gamme de densité de dépôt d’énergie allant de 0,3 à 1000 eV/nm.Dans le vivant, l’eau ayant une place prépondérante, la compréhension de la radiolyse de l’eau est essentielle. L’espèce la plus réactive produite en milieu aéré, le radical hydroxyle (HO•) a été quantifiée en utilisant une sonde spécifique, l’acide 3-coumarine-carboxylique.Les dégâts indirects aux biomolécules, via les espèces issues de la radiolyse de l’eau, ont été étudiés en solution aqueuse diluée sur deux systèmes : un acide aminé, la phénylalanine et une protéine, la myoglobine. Les effets directs de radiolyse ont été étudiés sur la myoglobine en gels concentrés hydratés. Les phénomènes de radiolyse ont été caractérisés pour décrire les mécanismes en jeu et les produits issus de la radiolyse de la phénylalanine ont été systématiquement identifiées et quantifiées. / The goal of this thesis is to achieve a better understanding of fundamental mechanisms of the radiolysis of biomolecules by accelerated ions, at the molecular scale. To do so, different type of ions have been used (H+, He2+, C6+) at various energies, corresponding to densities of energy deposition from 0,3 to 1000 eV/nm.The main component in biological systems is water. Therefore, the comprehension of the water radiolysis under ions irradiation is essential. One of the most reactive species produced in aerated conditions, the hydroxyl radical (HO•), has been quantified using a specific probe, the 3- carboxylic acid coumarin.Indirect effects of radiolysis on biomolecules, involving water radiolysis species, have been studied in dilute aqueous solutions on two different systems: phenylalanine, an amino acid, and a protein, myoglobin. Direct radiolysis effect were studied on concentrated hydrogels of myoglobin ad other proteins. Elucidation of radiolysis mechanisms and quantification of phenylalanine radiolysis products were systematically performed.

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No description available.