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Landfilling is the most common approach to dispose of municipal solid wastes but inevitably leads to leachate formation. Persistent UV quenching substances (UVQS) in landfill leachate can affect the effectiveness of UV disinfection in municipal wastewater treatment systems when leachate co-treatment is applied. Membrane electrochemical reactor (MER) treatment was investigated to reduce the UV quenching capability and simultaneously recover resources in the leachate as an effective onsite pre-treatment. Ion-selective membranes were used in this MER to create two different conditions: a low-pH anolyte for organic oxidation and a high-pH catholyte for ammonia recovery. The MER achieved significantly higher removals of both dissolved organic carbon and UV254nm absorbance than membrane-less electrochemical treatment. The MER was able to remove a large percentage of total nitrogen from the leachate while recovering about half of the influent ammonia in the catholyte with less specific energy consumption. The second study coupled MER with Fenton oxidation through providing synergistic benefits with the low solution pH, reduced organics, and ammonia removal. This two-stage coupled system reduced the more leachate COD than the standalone Fenton process treating raw leachate. Also, the usage of chemicals as Fenton reagents has been greatly reduced: FeSO4 and H2O2 by 39%, H2SO4 by 100%, and NaOH by 55%. Consequently, the sludge production was reduced by 51% in weight and 12% in volume. Despite electricity consumption by the MER, the coupled system cost $4.76 per m3 leachate less than the standalone Fenton treatment. More notably, direct Fenton oxidation removed only 21% of ammonia; in comparison, the MER-Fenton system removed ammonia by 98% with the possibility for recovery at a rate of 30.6 -55.2 kg N m-3 reactor d-1. Those results demonstrated that coupling MER with the Fenton process could mitigate some inherent drawbacks of Fenton oxidation such as ineffective ammonia removal, high acid and chemical reagents dose requirements, and a large amount of sludge generation. The third study investigated the formation of total halogenated organics (DBP) and the associated toxicity as the side effect of leachate treatment in the MER. Compared to the 4538±100 µg L-1 from the control membrane-less electrochemical oxidation reactor, the amount of DBP generated in the MER only accounted for 19.1±4.5 % after the same treatment period. The total toxicity value (26.6 ×10-3 ) was low for MER effluent, only 15.1% of that in the control group. Both high pH and high ammonia concentration introduced more DBP mass and toxicity production after MER treatment. DBP concentrations were shown to increase with applied current density and possible temperature raise. With 67.5% of DBP mass concentration and 74.4% of the additive toxicity removal, the granular activated carbon (GAC) electrode system was shown more effective than GAC adsorption alone in remediating DBP harmful effects. This dissertation introduced MER as a promising technology for the treatment of leachate through performance demonstration, process integration and by-product remediation. / Doctor of Philosophy / Municipal solid waste is often disposed of in landfills because of the most economics and convenience. However, one of the most challenging problems is the leachate formation and treatment. In the US, leachate is currently often diluted in domestic wastewater treatment systems; meanwhile, the persistent contaminants in landfill leachate can lower the effectiveness of UV disinfection and result in high cost and permit violation. In this study, the membrane electrochemical reactor (MER) using electricity as the driving force was applied to solve the issue and simultaneously recover valuable resources in the leachate. Membranes as a barrier for selective ions were used in this MER to create two different conditions with different purposes: a low-pH anolyte for organic oxidation and a high-pH catholyte for ammonia recovery. The MER achieved significantly higher contaminants removals than membrane-less electrochemical treatment. The second study coupled MER with one of the established advanced oxidation processes, also known as Fenton oxidation through providing mutual benefits with the low solution pH, reduced organics, and ammonia removal/recovery. This two-stage coupled system reduced the leachate contaminants effectively towards the direct discharge standard. In addition, the usage of chemical reagents, as well as the amount of process residual, has significantly been reduced. The third study investigated the formation of by-products as the side effect of leachate treatment in the MER. Compared to the membrane-less reactor, the undesirable by-products generated in the MER only accounted for one fifth after the same treatment period. A granular activated carbon electrode system was shown effective in remediating the harmful effects. This dissertation introduced MER as a promising technology for the treatment of leachate as one of the toughest wastewaters.

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2004-2005 / Les cancers cutanés sont associés à la formation des dimères cyclobutyliques de pyrimidine (DCP) générés par les ultraviolets (UV) du soleil. Nos résultats indiquent que les transversions T-->G retrouvées suite aux UVA sont dues aux DCP formés majoritairement sur les TT. Nous avons également démontré que, contrairement au dogme établi, les protéines réparant les mésappariements n'influencent pas la réparation des DCP. p53 a indéniablement une influence sur la réparation des DCP. Cependant, la lignée SW480, contenant un gène p53 double-muté, est fonctionnelle en réparation par excision de nucléotides des DCP. Normalement, un stress est nécessaire à l'activation des effecteurs de p53. Cependant, la protéine p53 double-mutée des SW480 active constitutivement p21, un effecteur de p53. L'activation des protéines réparant les DCP par p53 se fait probablement de la même façon que p21. L'éclaircissement de ces mécanismes a amené une meilleure compréhension de l'induction des cancers.

Le suivi règlementaire des sous-produits de la désinfection (SPD) dans l’eau potable fournit généralement aux opérateurs des usines de production d’eau potable un portrait partiel de la performance du traitement en termes de SPD, étant donné la basse fréquence d’échantillonnage exigée. Une rétroaction plus fréquente sur les concentrations de SPD permettrait une optimisation des paramètres d’opération susceptible d’influencer l’enlèvement des précurseurs de SPD et la désinfection. Il importe alors d’avoir une méthode de suivi simple, rapide, et à fréquence élevée, voire en continu, des concentrations de SPD dans l’eau potable. L’absorbance UV différentielle (ΔA) est une méthode d’estimation des concentrations de SPD à coût faible, pouvant être effectuée rapidement et fréquemment, qui consiste à utiliser la différence entre une mesure de l’absorbance UV avant la chloration et une mesure de l’absorbance UV après la chloration pour prédire les concentrations de SPD. L’objectif de cette thèse est de développer une stratégie de suivi en continu de la formation des SPD par l’absorbance UV différentielle en usine afin de permettre une opération préventive et adaptative lors du traitement de l’eau. Cet objectif est divisé en deux sous-objectifs: comprendre pourquoi les relations SPD-ΔA ne sont pas universelles et identifier les stratégies favorisant leur généralisation et leur application à l’échelle réelle, et développer une stratégie d’opération adaptative et préventive du procédé de coagulation-floculation, utilisant comme rétroaction l’absorbance UV-visible, afin de réduire les concentrations de SPD à l’usine et en réseau. À cette fin, un premier essai a été fait afin de vérifier la possibilité d’établir des relations SPD-ΔA valide à l’échelle réelle. Ensuite, une stratégie de coagulation à l’échelle réelle utilisant l’absorbance UV à 254 nm des eaux brutes et décantées a été testée. En parallèle, une série de jar-tests et d’essais de chloration faits sur 8 eaux brutes différentes a permis de construire une base de données sur la coagulation de la matière organique et des précurseurs des SPD, permettant de comparer les résultats obtenus en laboratoire à ceux obtenus à l’échelle réelle. Cette même base de données a aussi servi à établir des relations SPD-ΔA plus largement applicables et à formuler des recommandations sur l’approche à adopter pour généraliser et utiliser ces relations. Les résultats des essais à l’échelle réelle montrent qu’il est possible d’établir des relations SPD-ΔA autant pour des sous-produits règlementés (trihalométhanes (THM) et acides haloacétiques (AHA)) que pour des sous-produits émergents (haloacétonitriles (HAN), halocétone (HK), et chloropicrine (CPK)) en utilisant l’absorbance UV différentielle à une seule longueur d’onde (272 nm), mais que ces relations varient dans le temps en fonction des paramètres physico-chimiques de l’eau brute et des paramètres d’opération des procédés. L’absorbance UV avant chloration demeure malgré tout un bon indicateur de la concentration de précurseurs de SPD. Ainsi, une stratégie de coagulation basée sur une dose stœchiométrique d’alun par rapport à l’absorbance UV à 254nm de l’eau brute (dose d’alun/UV254 de l’eau brute) a été développée à l’échelle réelle. Les résultats de l’essai de la stratégie à l’échelle réelle et des jar-tests concordent et confirment que l’utilisation d’une dose stœchiométrique d’alun définie permet de maximiser l’enlèvement de l’absorbance UV et des précurseurs dans une situation de qualité de l’eau variable quotidiennement et saisonnièrement. L’utilisation de l’absorbance UV différentielle à plusieurs longueurs d’onde, en plus de l’utilisation de l’absorbance avant chloration, permet d’améliorer les prédictions des relations empiriques SPD-ΔA et de généraliser leur application. En effet, les résultats des jar-tests et des essais de chloration ont montré que ces relations sont applicables à des eaux chlorées ayant des caractéristiques physico-chimiques variées. Spécifiquement, les concentrations de THM semblent mieux prédites en utilisant l’absorbance avant chloration à 270 nm, ΔA à 270 nm et ΔA à 425 nm, l’acide dichloroacétique en utilisant l’absorbance avant chloration à 250nm, ΔA à 250 nm et ΔA à 425 nm, et l’acide trichloroacétique en utilisant l’absorbance avant chloration à 255 nm, ΔA à 255nm et ΔA à 425 nm. L’utilisation de l’absorbance différentielle à plusieurs longueurs d’onde devra être expérimentée à l’échelle réelle dans des recherches futures, entre autres en utilisant des sondes de mesure de l’absorbance en continu. / Regulatory sampling of drinking water for the control of disinfection by-products (DBPs) gives a partial depiction of the performance of a drinking water system in terms of DBPs, given the usually low sampling frequency required. A more frequent feedback on DBP concentrations would allow optimisation of the operation of the treatment processes responsible for the removal of DBP precursors. It is therefore important to develop a simple, rapid and high frequency or even continuous monitoring method for DBPs. Differential UV absorbance (ΔA) is a method, consisting of the use of the difference between the absorbance of a sample before chlorination and after chlorination to predict DBP concentrations that can provide such a feedback rapidly and frequently. The main goal of this thesis is to develop a continuous DBP monitoring strategy using differential UV absorbance in order to achieve a preventive and adaptive operation of water treatment processes. This goal is divided into two sub-objectives : to understand why DBP-ΔA relationships are not universal and to identify ways to generalize their application in full-scale water treatment facilities, and to develop a preventive and adaptive operation strategy of the coagulation-flocculation process, using UV absorbance as a feedback, in order to reduce DBP concentrations at the plant and in the distribution network. To reach these goals, atrial was made to assess the possibility of establishing DBP-ΔA relationships at a full-scale treatment plant. Then, a coagulation strategy using UV absorbance at 254 nm of the raw and settled waters was tested to assess its capacity to reduce DBP concentrations. At the same time, jar-tests and chlorination experiments were conducted on 8 different water sources to build a database on the coagulation of DBP precursors. These results were compared with the full-scale coagulation strategy. The database was also used to establish DBP-ΔA relationships applicable to waters with a wide range of physicochemical characteristics and to formulate recommendations on the approach to take to generalize and use these relationships. The results of the full-scale trials show that it is possible to establish DBP-ΔA relationships for both regulated (trihalomethanes (THM) and haloacetic acids (HAAs)) and unregulated (haloacetonitriles (HANs), haloketones (HKs) and chloropicrin (CPK)) DBPs using differential UV absorbance at one wavelength (272 nm), but that these relationships vary with the raw water physicochemical characteristics and with the operation parameters of the treatment process. Nonetheless, UV absorbance before chlorination remains a good surrogate of the concentration of DBP precursors. A coagulation strategy based on a stoichiometric alum dose related to UV absorbance at 254 nm (alum/UV254) was therefore developed at full-scale. Results from the full-scale trials and the jar-tests are coherent and confirm that using a stable stoichiometric dose maximises the removal of UV absorbance and DBP precursors despite daily and seasonal variations of raw water quality and natural organic matter content. The use of differential UV absorbance at multiple wavelength made it possible to improve the predictive capacity of empirical DBP-ΔA relationships and to generalize their application. Indeed, results from the jar-tests and chlorination experiments showed that these relationships are applicable to chlorinated waters with very different physicochemical characteristics. Specifically, THM concentrations seem to be better predicted using pre-chlorination absorbance at 270nm, ΔA at 270nm and ΔA at 425nm, dichloroacetic acid using pre-chlorination absorbance at 250nm, ΔA at 250nm and ΔA at 425nm, and trichloroacetic acid using pre-chlorination absorbance at 255nm, ΔA at 255nm and ΔA at 425nm. The use of differential absorbance at multiple wavelengths, especially using online absorbance probes, should be tried in a full-scale water treatment facility in future research.

The synergistic effect of nitric oxide toward dephosphorylation reactions involving phosphate esters was the subject of investigation in this research. Sodium nitroprusside under UV irradiations at 254nm, 365nm and white light was utilized as nitric oxide donor in solutions. The effects of cobalt trimethylenediamine and nitroprusside towards dephosphorylation of nitrophenylphosphate and pyrophosphate which were modeled as organophosphate ester substrates were also investigated. The activated substrate models showed more rate enhancement than the unactivated models in all cases. The direct interaction of nitric oxide with the phosphorus centre is presumed to be the reason for enhanced hydrolysis. This study demonstrates the possible role of nitric oxide in decontamination reactions of poorly biodegradable phosphate esters in the biosphere. / Chemistry / M. Sc. (Chemistry)

Formamide is a solvent of great interest to prebiotic chemists because it is liquid over a wide range, it is less volatile than either water or HCN, and it possesses a versatile reactivity. When formamide is heated in the presence of minerals or inorganic catalysts, a variety of products including purine nucleobases are generated. Irradiation of formamide reaction solutions with ultraviolet light increases the yield and diversity of products, and eliminates the need for a mineral catalyst. We have also performed formamide reactions in the presence of pyrite, a mineral which is likely to have been available on the primordial Earth, under a variety of atmospheric conditions. Our results indicate the greatest yield and diversity of products result from the combination of a pyrite mineral catalyst, heat, UV irradiation, and a carbon dioxide atmosphere. Purine nucleobases are simple to synthesize in model reactions and they stack well in aqueous solution; it has been hypothesized that the first nucleic acids were composed of only purine bases, and that water-soluble, cationic, aromatic molecules with large stacking surfaces (“”molecular midwives””) may have aided the assembly of the earliest nucleic acid analogs. We have characterized the interactions of various intercalators with a standard DNA duplex as well as with an antiparallel homopurine DNA duplex and have determined that molecules which possess four or more rings and a curved shape interact selectively with all-purine DNA; such molecules can serve as models for putative prebiotic midwives.

Erythema is a hallmark skin response to excessive ultraviolet radiation (UVR) and is associated with cutaneous inflammation. Both are mediated by inflammatory mediators including nitric oxide (NO), prostaglandin E2 (PGE2) and chemoattractants such as 12-hydroxyeicosatetraenoic acid (12-HETE) leading to vasodilation and increased leukocyte infiltration. The erythematous response is more pronounced in individuals with low basal melanin levels or who fail to respond to UVR with a robust up-regulation of melanogenesis. While melanin production is a key function of melanocytes, these cells can also produce NO and PGE2, and are located in close proximity to the dermal vasculature. It has been hypothesized that melanocytes with poor melanogenic capacity may participate in the inflammatory response to UVR. The aim of this project was to investigate the inflammatory response in the skin of individuals with either skin phototype (SPT) 1 or 4 to UVR. Sixteen normal healthy individuals were selected for study (8 SPT-1 & 8 SPT-4). Buttock skin was investigated by immunohistochemistry for leukocyte subtypes, eicosanoid producing enzymes and NO synthases under basal and UVR-stimulated conditions. In addition primary cultures of epidermal melanocytes (EM) were established from 16 individuals (8 SPT-1 & 8 SPT-4) and assessed for the presence of eicosanoid-producing enzymes, melanogenic enzymes and NO synthases, by immunocytochemistry, Polymerase Chain Reaction and Western Blotting and for the production of the main pro-inflammatory eicosanoid PGE2 by ELISA and Mass Spectrometry. Moreover, the fatty acid composition of cultured melanocytes was assessed by Gas Chromatography. Results showed that individuals with SPT-1 had significantly greater neutrophil infiltration into the epidermis than those with SPT-4 at 24 hrs post-UVR. Moreover, CD3+ lymphocyte infiltration into the dermis was significantly greater in individuals with SPT-4 than those with SPT-1 at 24 and 72 hrs post-UVR. NOS-1, NOS-3, 12-LOX and COX-2 expression were significantly increased in SPT-1 skin, while NOS-2 and 15-LOX were significantly increased in SPT-4 skin. As 12-LOX and COX-2 products are chemoattractive (for neutrophils) and pro-inflammatory respectively these data could explain the greater observed neutrophil infiltration in SPT-1. The 15-LOX product (15-HETE) is anti-inflammatory and may suggest that 15-LOX up-regulation in SPT-4 skin may aid resolution of the sunburn response, which in part may be mediated by CD3+ lymphocytes and a class-switch in eicosanoid production from COX to LOX products. Melanocyte primary cultures surprisingly showed that SPT was not correlated with melanin content or melanogenic enzyme expression/activity suggesting that all melanocytes in vitro contained the necessary cellular machinery to produce melanin. This finding may reflect also their equal treatment under these enriched culture conditions, which may or may not be available to these cells in situ. Moreover, all melanocytes expressed the necessary machinery (PLA2, COX-1, cPGES) to produce PGE2. However, only some cultures did so at baseline and in response to UVR, and this was not correlated with SPT. A positive correlation was found however between expression level of dopachrome tautomerase (DCT) and protection against PGE2 production in response to UVR, which may suggest a novel role for DCT unrelated to melanogenesis. In summary this research project has generated data that highlights differences between the skin of individuals with SPT-1 and those with SPT-4, and may provide evidence that the keratinocyte partner contributes significantly to the SPT-associated response. This research may also suggest DCT as a novel therapeutic target to protect EM from participation in the UVR-associated inflammatory response in skin.

Selective gas-phase dissociation strategies have been developed for the characterization of cross-linked peptides and proteins in quadrupole ion trap mass spectrometers. An infrared chromogenic cross-linker (IRCX) containing a phosphotriester afforded rapid differentiation of cross-linked peptides from unmodified ones in proteolytic digests of cross-linked proteins by selective infrared multiphoton dissociation (IRMPD). Only the cross-linked peptides containing the chromogenic phosphate underwent IRMPD and unmodified peptides were not affected by IR irradiation. IRMPD of IRCX-cross-linked peptides yielded uncross-linked y-ion sequence tags of the constituent peptides due to secondary dissociation of all primary product ions which contained the chromophore, thus allowing successful de novo sequencing of the cross-linked peptides. Peptides cross-linked via a two-step conjugation strategy through the formation of a bis-arylhydrazone (BAH) bond were selectively dissociated by ultraviolet radiation at 355 nm. The BAH-cross-linked peptides could be distinguished from not only unmodified peptides but also dead-end modified peptides based on the selectivity of ultraviolet photodissociation. In a complementary approach, electron transfer dissociation of BAH-cross-linked peptides resulted in preferential cleavage of the hydrazone bond which produced two modified peptides. These modified peptides were subsequently interrogated by CID which allowed for the original site of cross-linking to be pinpointed. IRMPD was implemented in a dual pressure linear ion trap to demonstrate successful photodissociation of peptides having modest absorptivities. Peptides were observed to efficiently dissociation by IR irradiation exclusively in the low pressure cell whereas no dissociation was observed in the high pressure cell due to extensive collisional cooling. IRMPD provided greater sequence coverage of the peptides than CID and yielded product ion mass spectra which were predominantly composed of singly charged product ions which simplified spectral interpretation. IRMPD was further applied for the sequencing of small-interfering RNA. Complete sequence coverage was obtained and the results were compared to CID. / text

Ce projet de thèse porte sur l'étude de la haute atmosphère de Titan à partir de mesures en laboratoire de sections efficaces d'absorption et de l'analyse des données de Cassini-UVIS.La caractérisation de l'instrument et des observations effectuées par UVIS était nécessaire. Les données provenant des canaux ultraviolet lointain (FUV) et ultraviolet extrême (EUV) d'UVIS ont été analysées et corrigées des effets instrumentaux. A partir de l'analyse de huit occultations solaires dans l'EUV, les profils de densité volumique de N2 et CH4 ont été déterminés par une méthode d'inversion avec régularisation. Les températures ont ensuite été obtenues à partir des profils de N2 en supposant une haute atmosphère isotherme. Les occultations stellaires dans le FUV ont été modélisés et une technique de détermination des densités caractérisée. La possibilité de détection de différentes molécules (dont certaines n'avaient jamais été observés par cette technique avant) a été analysée. Puis, en utilisant l'algorithme de minimisation de Levenberg-Marquardt, les profils de densité de colonne pour différents hydrocarbures et de profondeurs optiques pour les aérosols ont été obtenus à partir de données simulés. Les densités de colonne ont été inversées avec une procédure de régularisation afin d'obtenir des profils de densité volumique pour les hydrocarbures et des profils d'extinction pour les aérosols. La procédure a finalement été appliquée à deux occultations stellaires mesurées par UVIS. Les hydrocarbures étudiés sont CH4, C2H2, HCN, C2H4, C4H2, HC3N et C6H6.Les profils issus des occultations stellaires et solaires ont été obtenus pour différentes dates et des différents lieux. Les profils et les températures dérivés ont donc été analysés en fonction des variables géographiques et temporelles : latitude, longitude, date d'observation, etc. La variabilité atmosphérique est discutée à la lumière de ces résultats.Le benzène (C6H6), une molécule détectée dans l'atmosphère de Titan, est particulièrement importante car elle est considéré comme intermédiaire entre le gaz et la formation des particules solides. Des mesures de l'absorption du benzène dans le domaine ultraviolet, à des températures qui couvrent une gamme de température allant de l'ambiante à 215 K, ont été réalisées dans différentes installations internationales. A partir de ces mesures, la section efficace d'absorption du benzène a été déterminée et analysée en termes des transitions observées et en fonction de la température de mesure. Ces résultats ont été utilisés dans le calcul d'abondance de C6H6 dans la thermosphère de Titan comme indiqué dans les paragraphes précédents.En résumé, l'analyse des observations UVIS présentées contribuent à la caractérisation de la haute atmosphère à travers des profils de N2, de températures thermosphériques et des profils de différents hydrocarbures et nitrile. Ces données d'observation aideront à contraindre les modèles photochimiques. Les profils d'abondance donnés en fonction de différentes coordonnées géographiques et temporelles pourront être utilisés pour étudier plus avant la variabilité atmosphérique. Les résultats de ce travail aideront donc à la compréhension de la composition et la dynamique de l'haute atmosphère de Titan. Cette connaissance, combinée avec des informations sur la basse atmosphère et la surface de Titan, aidera à comprendre l'évolution de molécules organiques dans ce corps céleste abiotique voisin.Les résultats de ce travail aideront donc à la compréhension de la composition et la dynamique de la haute atmosphère de Titan. Cette connaissance, combinée avec des informations sur la basse atmosphère et la surface de Titan, aidera à comprendre l'évolution de molécules organiques dans ce corps céleste abiotique voisin