Dans les eaux naturelles ou bien dans les eaux en cours de traitement, de nombreux processus peuvent générer des espèces réactives telles que de l´oxygène singulet, des ions superoxydes,des radicaux hydroxyles, ou bien d’autres oxydants. Dans les eaux naturelles, ces processus impliquent les substances humiques ou les ions nitrates en présence de lumière et d´oxygène. Dans les eaux en cours de traitement, les procédés d’oxydation avancée sont une source de production de radicaux hydroxyle. D’autres radicaux peuvent ensuite être formés par des réactions secondaires avec la matrice inorganique des eaux. Ces réactions aboutissent à la formation de radicaux inorganiques tels que les radicaux carbonates CO3·- et les radicaux chlores Cl· (atome de chlore). La réactivité de ces derniers est mal connue. Ce travail a pour but d’étudier la réactivité des radicaux carbonates et chlores avec des pesticides de type phénylurées, utilisés comme molécules modèles, et d’identifier les produits de dégradation. Le radical carbonate a été généré par la photolyse de [Co(NH3)5CO3]+, par photosensibilisation à partir de la 4- carboxybenzophenone, de la 1-nitronaphtalène et de la duroquinone et par l’excitation UV du peroxyde d’hydrogène. Le radical chlore a été généré par l’excitation UV du peroxyde d’hydrogène. Les constantes de vitesse de réaction des radicaux carbonates et chlores avec les pesticides étudiés, ont été déterminées, après validation d’une méthode de cinétique compétitive ou par modélisation cinétique. Ces constantes sont comprises pour le radical carbonate dans l’intervalle 0,35-3,5.107 L mol-1 s-1, et dans l’intervalle 1,2-3,9.108 L mol-1 s-1 pour le radical chlore. La comparaison de la réactivité des radicaux carbonates et chlores avec celle des radicaux hydroxyles, indique un facteur de l’ordre de 1000 pour le radical carbonate et de 100 pour le radical chlore, et ceci en faveur de la réactivité des radicaux hydroxyles. Plusieurs produits de dégradation du radical carbonate ont été identifiés. Il s’agit de produits d’hydroxylation du cycle aromatique, des produits issus d’une déméthylation, un dérivé quinone imine pour le fénuron, la cassure du pont dissulfure pour le metsulfuron méthyl. La comparaison des produits de dégradation formés avec les radicaux carbonates et hydroxyles met en évidence certains produits communs aux deux processus tandis que d’autres sont plus spécifiques. Les produits issus du radical carbonate sont moins nombreux en nombre que ceux issus du radical hydroxyle. / In natural water, humic substances are a source of reactive species production, in the presence of light and oxygen, such as singlet oxygen, superoxide, hydroxyl radicals, hydrogen peroxide but also a plurality of inorganic radicals such as the carbonate and chlorine radicals. The reactivity of these is unknown. This work aims to study the reactivity of carbonate and chorine radicals with pesticide ofphenylurea type and identify the products of degradation. The carbonate radical was generated by the photolysis of [Co(NH3)5CO3]+, by photosensitization from 4-carboxybenzophenone, from 1-nitronaphtalene and from duroquinone and by UV excitation of hydrogen peroxide. The chlorine radical was generated by UV excitation of hydrogen peroxide. The rate constants for reaction with the carbonate and chlorine radicals with the pesticides were determined after validation of competitive kinetic or kinetic modeling. These constants are included of the carbonate radical in the range 0.35-3.5x107 mol-1 L s-1, and in the range fron 1,2-3,9x108 mol-1 L s-1 for the chlorine radical. The comparison between the reactivity of the carbonate and chlorine radicals with the hydroxyl radicals, shows a factor 1000 for the carbonate radical and 100 for the chorine radical for the reactivity of hydroxyl radicals. Several degradation products were identified from the carbonate radical. These products were the hydroxylation of the aromatic ring, the products of demethylation, a derivative quionone imine for fenuron, the breaking of the bridge dissulfure for metsulfuron methyl. The comparison of the degradation products formed with carbonate and hydroxyl radicals show some common products to both processes, and others products are more specific. The products from the carbonate radical are fewer in number than those resulting from the hydroxyl radical.

Dissolved organic carbon (DOC) is a sum parameter that is frequently used in water analytics. Highly resolved and accurate DOC data are necessary, for instance, for water quality monitoring and for the evaluation of the efficiency of treatment processes. The conventional DOC determination methods consist of on-site sampling and subsequent analysis in a stationary device in a laboratory. However, especially in regions where no or only poorly equipped laboratories are available, this method bears the risk of getting erroneous results. For this reason, the objective of the present study was to set up a reliable and portable DOC analyzer for on-site analysis. The presented DOC system is equipped with an electrolysis-based decomposition cell with boron-doped diamond electrodes (BDD) that oxidizes the organic compounds to carbon dioxide. Within this study, the influence of different electrode materials and the composition of the applied electrolytes on the DOC decomposition in an undivided electrolytic cell were systematically investigated. Furthermore, some technical aspects of the portable prototype are discussed. After a detailed validation, the prototype was used in an ongoing monitoring program in Northern India. The limit of detection is 0.1 mg L−1 C with a relative standard deviation of 2.3% in a linear range up to 1000 mg L C−1. The key features of the portable DOC analyzer are: No need for ultra-pure gases, catalysts or burning technology, an analyzing time per sample below 5 min, and a reliable on-site DOC determination.

Eutypa dieback, one of several grapevine trunk diseases (GTDs), is of serious concern to the grape industry globally. This disease is caused by the fungus Eutypa lata but it is often seen in consortia growth with Phaeoacremonium minimum and Phaeomoniella chlamydospora. It is vital to understand the mechanisms for how this disease functions to develop control measures to combat it. Brown rot fungi are able to use a complex of low molecular weight (LMW) metabolites to induce a Fenton reaction to deconstruct woody tissue. These metabolites are part of a chelator mediated Fenton (CMF) chemistry that produces reactive oxygen species that are capable of depolymerizing wood polymers. We propose that a mechanism similar to CMF chemistry may be occurring in grapevine trunk disease pathogens. This thesis investigates how LMW metabolites produced by the fungi contribute to the disease and decay progression in GTDs. Research on Mite control in the laboratory with abamectin was also investigated, as research in this area was required when mites infested our fungal cultures and suitable laboratory controls were not available. Research on the GTD fungi was initiated by first examining whether metabolites produced by the three fungi can function in a manner to promote reactions like the CMF system. We separated and identified specific metabolites that potentially could contribute to CMF chemistry. We found that all three GTD fungi were able to produced LMW metabolites that promoted CMF chemistry, and we hypothesized that this mechanism contributes to processes leading to tissue necrosis in grapevine trunk wood. To explore the development of effective control measures based on this newly discovered mechanism for pathogenesis, we also explored the use of antioxidant/chelator compounds, BHA and BHT, in the control of the consortia fungi. Biocontrol organisms, Bacillus subtilis and Trichoderma atroviride, that produce antioxidants were also tested as biocontrols against the fungi involved in Eutypa Dieback disease. We found that BHA was highly effective in inhibiting fungal growth for all three fungi at concentrations higher than 0.5mM, and both B. subtilis and T. atroviride proved to be effective biocontrol agents in inhibiting E. lata, P. minimum, and P. chlamydospora.

Presented Diploma Thesis is focused on the development, characterization, and utilization of simple and inexpensive electrochemical DNA biosensor for the detection of DNA damage caused by oxidative stress. The initial part of the work is devoted to preparation and characterization of a large-surface carbon film electrode (ls-CFE) modified with carbon nanotubes (CNT/ls-CFE). Carbon nanotubes improve electrochemical properties of the transducer and increase the amount of adsorbed DNA on the electrode surface. Testing of the electrode surface modified with multiwalled carbon nanotubes (MWCNT) was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using a redox system [Fe(CN)6]4-/3- and using square wave voltammetry without any redox indicator. Carbon nanotubes have proved to be unsuitable material for our type of biosensor, but it can be used inanalytical chemistry for the determination of electroactive substances. The second part of this Thesis deals with the application of the prepared DNA biosensor for the detection of DNA damage by oxidative stress. The biosensor based on the ls-CFE was chosen for this purpose, having several advantages, such as its fast preparation, a simple mechanical renewal of the electrode surface, a good reproducibility of measurements,...

L’oxydation photocatalytique des Composés Organiques Volatils (COVs) apparaît comme un procédé très prometteur pour la réduction de la pollution atmosphérique. Ce travail avait pour objectif d’étudier l’oxydation photocatalytique de plusieurs COVs au sein d’un réacteur annulaire: méthyléthylcétone (MEK), acétone, 1-propanol ou encore triéthylamine (TEA). Dans une première partie, l’influence de plusieurs paramètres cinétiques tels que la concentration en polluant, l’intensité lumineuse, le temps de contact et le taux d’humidité a été étudiée. Un mécanisme de dégradation photocatalytique a été établi pour chaque polluant en fonction des sous-produits détectés par GC/MS. Dans une seconde partie, la diffusion de radicaux hydroxyles OH• dans la phase gazeuse, après activation photonique du TiO2, a été mise en évidence par Fluorescence Induite par Laser (LIF). Pour la première fois, ces radicaux OH• ont été détectés à des pressions proches des conditions atmosphériques. Dans ce cas, nous pouvons en conclure que la dégradation photocatalytique des COVs pourrait être partiellement due à une réaction en phase gazeuse entre les COVs et les radicaux OH• / Photocatalytic oxidation of airborne contaminants appears to be a promising process for remediation of air polluted by Volatile Organic Compounds (VOCs). The aim of our study is the photocatalytic oxidation of several VOCs using an annular reactor: methylethylketone (MEK), acetone, 1-propanol and triethylamine (TEA). First, the influence of different kinetic parameters such as pollutant concentration, incident light irradiance, contact time and humidity has been studied. A mechanistic pathway has been indeed proposed for each pollutant according to the produced intermediates species detected by GC/MS. Second, the diffusion of hydroxyls radicals OH• in gas phase, after photonic activation of TiO2, has been highlighted using Laser-Induced Fluorescence (LIF). For the first time, OH• radicals have been detected at atmospheric pressures, close to the major photocatalytic oxidation conditions, leading to the assumption that the photocatalytic degradation of VOCs might be at least partially occurs between pollutants and OH• radicals in gas-phase

Presented Ph.D. Thesis is focused on the development of analytical methods applicable for determination of selected xenobiotic compounds and for monitoring DNA damage they can induce. The main attention has been paid to the development and testing of non-toxic electrode materials for preparation of miniaturized electrochemical devices and novel electrochemical DNA biosensors. 2-Aminofluoren-9-one (2-AFN) was selected as a model environmental pollutant, which belongs to the group of hazardous genotoxic substances. Its carcinogenic and mutagenic effects may represent a risk to living and working environment. 2-AFN has one oxo group, where the cathodic reduction occurs, and one amino group, where the anodic oxidation occurs. The voltammetric behavior of 2-AFN in the negative potential region was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) representing a non-toxic and more mechanically robust alternative to mercury electrodes. This working electrode was subsequently used for the development of a newly designed miniaturized electrode system (MES), which has many benefits as the possibility of simple field measurements, easy portability, and the measurement in sample volume 100 µL. Moreover, a glassy carbon electrode (GCE) was used for further investigation of...

Abstract: Monte Carlo simulations were used here to compare the radiation chemistry of pure water and aqueous bromide solutions after irradiation with two different types of radiation, namely, tritium β-electrons (~7.8 keV) and [superscript 60]Co γ-rays/fast electron (~1 MeV) or high energy protons. Bromide ions (Br-) are known to be selective scavengers of hydroxyl radicals •OH precursors of hydrogen peroxide H[subscript 2]O[subscript 2]. These simulations thus allowed us to determine the yields (or G-values) of H[subscript 2]O[subscript 2] in the radiolysis of dilute aqueous bromide solutions by the two types of radiations studied, the first with low linear energy transfer (LET) (~0.3 keV/μm) and the second with high LET (~6 keV/μm) at 25 °C. This study was carried out under a wide range of Br- concentrations both in the presence and the absence of oxygen. Simulations clearly showed that irradiation by tritium β-electrons favored a clear increase in G(H[subscript 2]O[subscript 2]) compared to [superscript 60]Co γ-rays. We found that these changes could be related to differences in the initial spatial distributions of radiolytic species (i.e., the structure of the electron tracks, the low-energy β-electrons of tritium depositing their energy as cylindrical “short tracks” and the energetic Compton electrons produced by γ-radiolysis forming mainly spherical “spurs”). Moreover, simulations also showed that the presence of oxygen, a very good scavenger of hydrated electrons (e-[subscript aq]) and H• atoms on the 10[superscript-7] s time scale (i.e., before the end of spur expansion), protected H[subscript 2]O[subscript 2] from further reactions with these species in the homogeneous stage of radiolysis. This protection against e-[subscript aq] and H• atoms therefore led to an increase in the H[subscript 2]O[subscript 2] yields at long times, as seen experimentally. Finally, for both deaerated and aerated solutions, the H[subscript 2]O[subscript 2] yield in tritium β-radiolysis was found to be more easily suppressed than in the case of cobalt-60 γ-radiolysis, and interpreted by the quantitatively different chemistry between short tracks and spurs. These differences in the scavengeability of H[subscript 2]O[subscript 2] precursors in passing from low-LET [superscript 60]Co γ-ray to high-LET tritium β-electron irradiation were in good agreement with experimental data, thereby lending strong support to the picture of tritium-β radiolysis in terms of short tracks of high local LET. / Résumé: Les simulations Monte Carlo constituent une approche théorique efficace pour étudier la chimie sous rayonnement de l'eau et des solutions aqueuses. Dans ce travail, nous avons utilisé ces simulations pour comparer l’action de deux types de rayonnement, à savoir, le rayonnement γ de [indice supérieur 60]Co (électrons de Compton ~1 Me V) et les électrons β du tritium (~ 7,8 keV), sur la radiolyse de l’eau et des solutions aqueuses diluées de bromure. Les ions Br- sont connus comme d’excellents capteurs des radicaux hydroxyles •OH, précurseurs du peroxyde d’hydrogène H[indice inférieur 2]O[indice inférieur 2]. Les simulations Monte Carlo nous ont donc permis de déterminer les rendements (ou valeurs G) de H[indice inférieur 2]O[indice inférieur 2] à 25 °C pour les deux types de rayonnements étudiés, le premier à faible transfert d'énergie linéaire (TEL) (~0,3 keV/μm) et le second à haut TEL (~6 keV/μm). L’étude a été menée pour différentes concentrations d’ions Br-, à la fois en présence et en absence d'oxygène. Les simulations ont montré que l’irradiation par les électrons β du tritium favorisait nettement la formation de H[indice inférieur 2]O[indice inférieur 2] comparativement aux rayons γ du cobalt. Ces changements ont pu être reliés aux différences qui existent dans les distributions spatiales initiales des espèces radiolytiques (i.e., la structure des trajectoires d'électrons, les électrons β du tritium déposant leur énergie sous forme de «trajectoires courtes» de nature cylindrique, et les électrons Compton produits par la radiolyse γ formant principalement des «grappes» de géométrie plus ou moins sphérique). Les simulations ont montré également que la présence d'oxygène, capteur d’électrons hydratés et d’atomes H• sur l'échelle de temps de ~10[indice supérieur -7] s (i.e., avant la fin des grappes), protégeait H[indice inférieur 2]O[indice inférieur 2] d’éventuelles réactions subséquentes avec ces espèces. Une telle «protection» conduit ainsi à une augmentation de G(H[indice inférieur 2]O[indice inférieur 2]) à temps longs. Enfin, en milieu tant désaéré qu’aéré, les rendements en H[indice inférieur 2]O[indice inférieur 2] obtenus lors de la radiolyse par les électrons β du tritium ont été trouvés plus facilement supprimés que lors de la radiolyse γ. Ces différences dans l’efficacité de capture des précurseurs de H[indice inférieur 2]O[indice inférieur 2] ont été interprétées par les différences quantitatives dans la chimie intervenant dans les trajectoires courtes et les grappes. Un excellent accord a été obtenu avec les données expérimentales existantes.