Titre de l'écran-titre (visionné le 26 avril 2023) / L'amarante tuberculée (Amaranthus tuberculatus var. rudis), une mauvaise herbe envahissante introduite depuis 2017 au Québec, est résistante à cinq groupes d'herbicides de synthèse utilisés couramment en agriculture. Des tests moléculaires diagnostiques sont actuellement disponibles pour détecter la résistance de l'amarante à plusieurs herbicides et adapter au besoin les stratégies de désherbage en contexte agricole. Toutefois, aucun test n'est disponible encore pour tester la résistance de cette plante aux herbicides du Groupe 27 ou encore à l'un des deux mécanismes identifiés qui confèrent la résistance aux herbicides du Groupe 5. Afin de développer éventuellement des tests diagnostiques pour la résistance aux herbicides des Groupes 5 et 27 chez l'amarante tuberculée, ce projet avait pour objectif de caractériser le profil transcriptomique de clones d'amarante résistants à l'atrazine, un herbicide du Groupe 5, ou à la mésotrione, un herbicide du Groupe 27. Les objectifs spécifiques du projet étaient (1) d'établir un portrait transcriptomique sommaire de la plante en réaction à l'atrazine ou à la mésotrione; et (2) d'identifier des gènes marqueurs éventuellement utiles pour la mise au point de tests de résistance aux deux mêmes herbicides. Des plantes-mères confirmées résistantes ont été pulvérisées avec les deux herbicides et des échantillons foliaires ont été prélevés avant et après traitements. Un séquençage de type RNAseq a été réalisé ensuite pour caractériser le profil transcriptomique des individus résistants et sensibles, à l'aide d'algorithmes bio-informatiques pour l'identification des gènes exprimés différentiellement. En bref, aucune réponse compensatoire généralisée n'a été constatée chez les individus résistants en réponse aux traitements herbicides. En revanche, la surexpression constitutive d'une glutathion-S-transférase ('At.05g111120') possiblement impliquée dans la métabolisation du composé toxique a été a été observée chez les clones résistants à l'atrazine. De manière similaire, la surexpression du gène d'une cytochrome P450 ('At.00g045440') en réponse à l'herbicide et la surexpression constitutive de deux autres isoformes de la même enzyme ('At.00g045450' et 'At.02g067460') ont été observées chez les clones résistants à la mésotrione. Des études complémentaires seront maintenant bienvenues pour confirmer le potentiel des gènes identifiés comme marqueurs moléculaires pour la mise au point de tests de résistance moléculaires diagnostiques pour l'atrazine et la mésotrione.

Call number: LD2668 .T4 1985 G672 / Master of Science

The physiological responses of Myriophyllum spicatum to 2,4-D, diquat and copper were quantified using a plant tissue viability assay, and daily measures of dissolved oxygen and pH. Correlations of herbicide tissue residues to physiological response measures were determined and the relationship was used to develop exposure-response models. Diquat and copper had a greater effect on plant tissue viability than was observed for 2,4-D. Diquat produced greater reductions in dissolved oxygen concentrations and pH values than 2,4-D or copper. Copper exposure had the least effect on these parameters. Exposure-response models developed for 2,4-D predicted effective control at plant tissue residues ranging from 4000 to 4700 mg/kg. Aqueous exposure concentrations necessary to produce effective control plant tissue residues ranged from 0.20 to 0.40 mg/L. Exposure-response models developed for diquat predicted effective control at plant tissue residues ranging from 225 to 280 mg/kg. Aqueous exposure concentrations necessary to produce effective control plant tissue residues ranged from 0.113 to 0.169 mg/L. Exposure-response models developed for copper predicted effective control at plant tissue residues ranging from 680 to 790 mg/kg. Aqueous exposure concentrations necessary to produce effective control plant tissue residues ranged from 0.32 to 0.64 mg/L. Model predictions for 2,4-D, diquat and copper were within 0.5 mg/L of the manufacturers' label recommendations for these herbicides. The use of laboratory microcosms in development of exposure-response models for diquat and copper produced results comparable to those using the larger-scale greenhouse systems. Diquat effectively controlled M. spicatum at lower tissue residues than 2,4-D or copper. In addition, initial aqueous exposure concentrations were also lower for diquat. Use of these models in field situations should be coupled with considerations of quantity of biomass present and environmental conditions, such as turbidity, in order to accurately calculate exposure concentrations necessary for effective tissue residues. Thus, the use of these models can be used to optimize the impact on the target species while minimizing exposure for nontarget species.

Canada fleabane is the second glyphosate-resistant (GR) weed species to be confirmed in Ontario. In 2010, GR populations were identified at eight sites in Essex County. In 2011 and 2012, 147 additional sites across eight counties were confirmed to be resistant. Twelve and seven sites were identified with multiple resistance (glyphosate and cloransulam) in 2011 and 2012, respectively, across five counties. In soybeans, preplant tankmixes of glyphosate (900 g a.e.ha-1) plus saflufenacil (25 g a.i. ha-1), saflufenacil/dimethenamid-p (245 g a.i. ha-1), metribuzin (1120 g a.i. ha-1), or flumetsulam (70 g a.i. ha-1) provided greater than 87% up to 8 weeks after application (WAA). Glyphosate rates 21 to 48X the label rate (900 g a.e. ha-1) were required for 95% control. Postemergence tankmixes did not provide acceptable control. In dicamba-tolerant soybean, dicamba applied preplant at 600 g a.e. ha-1 provided the most consistent control of GR Canada fleabane. / Monsanto Canada Inc., Grain Farmers of Ontario, Agricultural Adaptation Council

Comprendre le transport des pesticides est crucial pour évaluer leur impact écologique. Les connaissances sur la variabilité spatiale des dépôts de pesticides, l'impact de l'érosion sur leur export et leur dégradation in situ restent très limitées à l'échelle des bassins versants. La caractérisation expérimentale et la modélisation ont donc été combinées à deux échelles, parcelle et bassin versant, dans deux contextes agricoles. Un formalisme a été développé pour prédire le transport des pesticides par ruissellement et a été intégré dans le modèle LISEM (LImbourg Soil Erosion Model). Les résultats montrent que les surfaces imperméables contribuent significativement à la masse exportée par ruissellement du vignoble. La partition des pesticides entre phase dissoute et particulaire diffère considérablement selon les molécules et le forçage hydrologique, et la présence de produits de dégradation et un enrichissement en R-métolachlore ont été observés ce qui souligne le potentiel des analyses énantiomériques pour évaluer la biodégradation des pesticides. Globalement, cette étude a démontré que la combinaison des échelles et des approches permet une meilleure compréhension du transport des pesticides. / Understanding pesticide transport is crucial to evaluate their ecological impact on ecosystems. Current knowledge on the spatial variability of pesticide deposition, the impact of erosion on pesticides export and the in situ pesticide degradation is very limited at the catchment scale. In this thesis, characterisation and modeling at two scales, the plot and catchment, were combined in two agricultural contexts. A formalism was developed to predict pesticide transport in runoff and was integrated in LISEM (LImbourg Soil Erosion Model). The results show that impermeable roads contributed to more than 40% to the overall load of fungicides exported via runoff from the vineyard. Pesticide partitioning between suspended solids and runoff water differed largely according to the molecules and the hydrological dynamics. The occurrence of degradation products and the enrichment of one enantiomer were observed suggesting the potential of chiral analyses for assessing biodegradation of chiral pesticides at such scale. Overall, the investigation demonstrated that combining different approaches enable a better understanding of pesticide transport.

Made available in DSpace on 2016-12-08T16:44:50Z (GMT). No. of bitstreams: 1 PGPV15MA174.pdf: 1010429 bytes, checksum: fe034957a32c1a3a626fd5db5aa86b68 (MD5) Previous issue date: 2015-06-18 / Weeds can cause significant yield losses in the agriculture, among them we can point out morning-glory species in many crops. To control that weed, we can use herbicides inhibiting protoporphyrinogen IX oxidase, in a selective way for a variety of crops. The objectives were: (i) to relate the response of Ipomoea hederifolia and Ipomoea quamoclit with the variation of doses of carfentrazone-ethyl and saflufenacil, of spray temperature at the moment of spraying, and of spray volume used; and (ii) to compare the efficacy of those herbicides sprayed isolately or mixed to glyphosate. Experiments were carried out from dose-response with carfentrazone-ethyl (0, 0.25, 0.5, 1, 2, 4, 5, 7.5, 10, 20, 35, 50, and 75 g ha-1 of the labeled herbicide Aurora®, 400 g a.i. L-1, FMC) and with saflufenacil (0, 0.125, 0.25, 0.5, 1, 2, 2.5, 5, 7.5, 10, 20, 35, and 50 g ha-1 of the labeled herbicide Heat®, 700 g a.i. kg-1, Basf), of variation of spray temperature (10 to 30 oC) and of variation of spraying volume (150 to 250 L ha-1). Evaluations were performed 14 days after spraying. In spite of showing differential response in relation to the dry mass accumulation, doses from 4 mL ha-1 of Aurora® and 5 g ha-1 of Heat® killed plants for both I. hederifolia and I. quamoclit. For carfentrazone-ethyl, increasing 10 L ha-1 in the spray volume reduced dry mass by 1.43% and 1.26% for I. hederifolia and I. quamoclit, respectively, while for saflufenacil, the reduction was by 12.73% and 11.30%, respectively for both species. For carfentrazone-ethyl, increasing 1 oC of spray temperature of reduced the dry mass by 0.22% and 0.35% for I. hederifolia and I. quamoclit, respectively, while for saflufenacil the reduction was by 0.56% and 0.30%, respectively for both species. The mix of carfentrazone-ethyl or saflufenacil with glyphosate provided a reduction by, at least, 10% greater of dry mass of I. hederifolia. We concluded that: carfentrazone-ethyl and saflufenacil are highly efficient to control I. hederifolia and I. quamoclit; increasing the spray volume and spray temperature provide greater efficacy to control both species, for both herbicides; and the mix with glyphosate improve the efficacy of controlling I. hederifolia for both herbicides / As plantas daninhas podem causar perdas significativas de produtividade na agricultura, dentre as quais se destacam as cordas-de-viola em diversos cultivos. Para seu controle podem ser utilizados herbicidas inibidores da enzima protoporfirinogênio IX oxidase, de maneira seletiva para diversos cultivos. Os objetivos foram: (i) relacionar a resposta de Ipomoea hederifolia e Ipomoea quamoclit com a variação da dose de carfentrazone-ethyl e saflufenacil, da temperatura da calda no momento da aplicação e do volume de calda aplicado; e (ii) comparar a eficácia destes herbicidas aplicados isoladamente e em mistura com glyphosate. Foram realizados experimentos de dose-resposta com carfentrazone-ethyl (0; 0,25; 0,5; 1; 2; 4; 5; 7,5; 10; 20; 35; 50 e 75 g ha-1 do produto comercial Aurora®, 400 g i.a. L-1, FMC) e com saflufenacil (0; 0,125; 0,25; 0,5; 1; 2; 2,5; 5; 7,5; 10; 20; 35 e 50 g ha-1 do produto comercial Heat®, 700 g i.a. kg-1, Basf), de variação de temperatura de calda (10 a 30 oC) e de variação de volume de calda (150 a 250 L ha-1). Avaliações de massa seca foram efetuadas 14 dias após a aplicação. Apesar de apresentarem resposta diferenciada quanto ao acúmulo de massa seca, doses a partir de 4 mL ha-1 de Aurora® e 5 g ha-1 de Heat® causaram a morte de plantas de I. hederifolia e I. quamoclit. Para carfentrazone-ethyl, o aumento de cada 10 L ha-1 no volume de calda aplicado reduziu a massa seca em 1,43% e 1,26% para I. hederifolia e I. quamoclit, respectivamente; enquanto para saflufenacil, a redução foi de 12,73% e 11,30%, respectivamente para essas espécies. Para carfentrazone-ethyl, o aumento de cada 1 oC na temperatura da calda reduziu a massa seca em 0,22% e 0,35% para I. hederifolia e I. quamoclit, respectivamente, enquanto para saflufenacil a redução foi de 0,56% e 0,30%, respectivamente para essas espécies. A mistura de carfentrazone-ethyl ou saflufenacil com glyphosate proporcionou redução de no mínimo 10% maior na massa seca de I. hederifolia. Conclui-se que: carfentrazone-ethyl e saflufenacil são altamente eficazes no controle de I. hederifolia e I. quamoclit; o aumento no volume de calda e na temperatura da calda proporcionam maior eficácia de controle dessas espécies, para ambos os herbicidas; e a mistura com glyphosate aumenta a eficácia de controle de I. hederifolia para ambos os herbicidas

Euphorbia heterophylla (EPHHL) é uma importante planta daninha na agricultura mundial, e a resistência aos herbicidas dificulta ainda mais o seu controle. Assim, conhecer o nível de resistência, os seus mecanismos e a persistência destas populações resistentes nas lavouras é fundamental para o estabelecimento de estratégias de prevenção e manejo. Foram realizados experimentos, objetivando estudar a resistência de EPHHL aos herbicidas inibidores da ALS e PROTOX nos níveis bioquímico, de planta e populacional. O capítulo I objetivou confirmar a ocorrência de resistência aos inibidores da ALS e determinar se existe resistência cruzada aos herbicidas dos grupos químicos das imidazolinona, sulfoniluréia, pirimidil-benzoato e sulfonanilida em biótipos de EPHHL com resistência múltipla (ALS e PROTOX). O capítulo II objetivou confirmar a existência de novos biótipos de EPHHL com resistência a PROTOX nos estados do Paraná e Rondônia e determinar se existe resistência cruzada aos herbicidas dos grupos químicos difeniléteres, ftalamida, triazolinona, oxadiazol e pirimidinedione. O capítulo III objetivou comparar a atividade da enzima ALS de biótipos com resistência múltipla com biótipo suscetível, na ausência e na presença dos herbicidas inibidores enzimáticos imazapyr, imazethapyr e nicosulfuron. O capítulo IV objetivou caracterizar as atividades das enzimas peroxidase, catalase e superóxido dismutase, em biótipos de EPHHL suscetível e com resistência múltipla, pela aplicação de herbicidas inibidores da PROTOX. E o capítulo V objetivou identificar a persistência de populações resistentes aos inibidores da ALS de EPHHL em lavouras da região Sudoeste e Oeste do Paraná que apresentavam resistência em levantamento prévio e verificar a existência de resistência de EPHHL ao glifosato nestas lavouras. Os resultados destes capítulos confirmaram que os biótipos de EPHHL Bom Sucesso do Sul, Vitorino, Vilhena e Medianeira, com suspeita de resistência múltipla aos inibidores da ALS e PROTOX, apresentam a resistência aos herbicidas inibidores da ALS e da PROTOX e esta sendo cruzada aos 4 grupos químicos dos inibidores da ALS e aos 5 grupos químicos dos inibidores da PROTOX, testados. A resistência dos biótipos de EPHHL aos inibidores da ALS é atribuída à menor sensibilidade da enzima a estes herbicidas. A atividade das enzimas antioxidantes superóxido dismutase, peroxidase e catalase, para os biótipos resistentes e suscetível é dependente do herbicida e da dose utilizada e pode ser um dos mecanismos envolvidos na resistência aos inibidores da PROTOX. Os biótipos de EPHHL resistentes aos herbicidas inibidores da ALS permanecem nas áreas mesmo após longo período de constatação da resistência. Plantas de EPHHL com resistência aos inibidores da PROTOX também permanecem nas áreas, no entanto em menor frequência. / Euphorbia heterophylla (EPHHL) is an important weed species in world agriculture and its control becomes difficult due to herbicide resistance. To develop proper EPHHL management strategies it is important to know the level and the mechanisms of resistance and persistence of resistant populations in the fields. Experiments were carried out to study the resistance of EPHHL to ALS and PROTOX inhibitors at biochemical, plant and population levels. The objectives on chapter I are to confirm the occurrence of resistance to ALS inhibitors and to determine whether there is cross resistance to other chemical groups, such as imidazolinone, sulfonylurea, pyrimidinyl (thio) benzoates and triazolopyrimidines in biotypes of EPHHL with multiple resistance (ALS and PROTOX). The objectives on chapter II are to confirm the existence of new EPHHL biotypes with resistance PROTOX in the states of Paraná and Rondônia and to determine whether there is cross resistance to other chemical group, such as diphenyl ethers, N-phenyl-phthalimide, triazolinone, oxadiazole and pyrimidinedione. The objectives on chapter III are to evaluate the activity of the ALS enzyme from biotypes with multiple resistance and to compare it to the enzyme activity of susceptible population in the absence and in the presence of the herbicides imazapyr, imazethapyr and nicosulfuron. The objectives on chapter IV is to characterize the activity of several antioxidant enzymes, such as peroxidase, catalase and superoxide dismutase in EPHHL biotypes treated with PROTOXinhibiting herbicides. The objective on chapter V are to identify the persistence of EPHHL populations resistant to ALS inhibitors on fields from Southwest and Western Paraná that were resistant in a previous survey and check for resistance to glyphosate in EPHHL these crops. The results support the hypothesis that EPHHL biotypes from Bom Sucesso do Sul, Vitorino, Vilhena and Medianeira have multiple resistance to ALS and PROTOX inhibitors. Four EPHHL biotypes are cross-resistant to all ALS chemical groups and five populations are cross-resistant to the PROTOX inhibitors tested. The resistance to ALS inhibitors on the EPHHL biotypes evaluated is attributed to the lower sensitivity of the herbicide target enzyme. The activity of all antioxidant enzymes, both on the resistant and susceptible biotypes, is dependent of the herbicide and on the dose used and can be one of the mechanisms of resistance to PROTOX inhibitors. The biotypes of EPHHL resistant to ALS-inhibiting herbicides remain in the area even after long-term observation of resistance. The resistance to PROTOX inhibitors also remains in areas, but less frequently.

Euphorbia heterophylla (EPHHL) é uma importante planta daninha na agricultura mundial, e a resistência aos herbicidas dificulta ainda mais o seu controle. Assim, conhecer o nível de resistência, os seus mecanismos e a persistência destas populações resistentes nas lavouras é fundamental para o estabelecimento de estratégias de prevenção e manejo. Foram realizados experimentos, objetivando estudar a resistência de EPHHL aos herbicidas inibidores da ALS e PROTOX nos níveis bioquímico, de planta e populacional. O capítulo I objetivou confirmar a ocorrência de resistência aos inibidores da ALS e determinar se existe resistência cruzada aos herbicidas dos grupos químicos das imidazolinona, sulfoniluréia, pirimidil-benzoato e sulfonanilida em biótipos de EPHHL com resistência múltipla (ALS e PROTOX). O capítulo II objetivou confirmar a existência de novos biótipos de EPHHL com resistência a PROTOX nos estados do Paraná e Rondônia e determinar se existe resistência cruzada aos herbicidas dos grupos químicos difeniléteres, ftalamida, triazolinona, oxadiazol e pirimidinedione. O capítulo III objetivou comparar a atividade da enzima ALS de biótipos com resistência múltipla com biótipo suscetível, na ausência e na presença dos herbicidas inibidores enzimáticos imazapyr, imazethapyr e nicosulfuron. O capítulo IV objetivou caracterizar as atividades das enzimas peroxidase, catalase e superóxido dismutase, em biótipos de EPHHL suscetível e com resistência múltipla, pela aplicação de herbicidas inibidores da PROTOX. E o capítulo V objetivou identificar a persistência de populações resistentes aos inibidores da ALS de EPHHL em lavouras da região Sudoeste e Oeste do Paraná que apresentavam resistência em levantamento prévio e verificar a existência de resistência de EPHHL ao glifosato nestas lavouras. Os resultados destes capítulos confirmaram que os biótipos de EPHHL Bom Sucesso do Sul, Vitorino, Vilhena e Medianeira, com suspeita de resistência múltipla aos inibidores da ALS e PROTOX, apresentam a resistência aos herbicidas inibidores da ALS e da PROTOX e esta sendo cruzada aos 4 grupos químicos dos inibidores da ALS e aos 5 grupos químicos dos inibidores da PROTOX, testados. A resistência dos biótipos de EPHHL aos inibidores da ALS é atribuída à menor sensibilidade da enzima a estes herbicidas. A atividade das enzimas antioxidantes superóxido dismutase, peroxidase e catalase, para os biótipos resistentes e suscetível é dependente do herbicida e da dose utilizada e pode ser um dos mecanismos envolvidos na resistência aos inibidores da PROTOX. Os biótipos de EPHHL resistentes aos herbicidas inibidores da ALS permanecem nas áreas mesmo após longo período de constatação da resistência. Plantas de EPHHL com resistência aos inibidores da PROTOX também permanecem nas áreas, no entanto em menor frequência. / Euphorbia heterophylla (EPHHL) is an important weed species in world agriculture and its control becomes difficult due to herbicide resistance. To develop proper EPHHL management strategies it is important to know the level and the mechanisms of resistance and persistence of resistant populations in the fields. Experiments were carried out to study the resistance of EPHHL to ALS and PROTOX inhibitors at biochemical, plant and population levels. The objectives on chapter I are to confirm the occurrence of resistance to ALS inhibitors and to determine whether there is cross resistance to other chemical groups, such as imidazolinone, sulfonylurea, pyrimidinyl (thio) benzoates and triazolopyrimidines in biotypes of EPHHL with multiple resistance (ALS and PROTOX). The objectives on chapter II are to confirm the existence of new EPHHL biotypes with resistance PROTOX in the states of Paraná and Rondônia and to determine whether there is cross resistance to other chemical group, such as diphenyl ethers, N-phenyl-phthalimide, triazolinone, oxadiazole and pyrimidinedione. The objectives on chapter III are to evaluate the activity of the ALS enzyme from biotypes with multiple resistance and to compare it to the enzyme activity of susceptible population in the absence and in the presence of the herbicides imazapyr, imazethapyr and nicosulfuron. The objectives on chapter IV is to characterize the activity of several antioxidant enzymes, such as peroxidase, catalase and superoxide dismutase in EPHHL biotypes treated with PROTOXinhibiting herbicides. The objective on chapter V are to identify the persistence of EPHHL populations resistant to ALS inhibitors on fields from Southwest and Western Paraná that were resistant in a previous survey and check for resistance to glyphosate in EPHHL these crops. The results support the hypothesis that EPHHL biotypes from Bom Sucesso do Sul, Vitorino, Vilhena and Medianeira have multiple resistance to ALS and PROTOX inhibitors. Four EPHHL biotypes are cross-resistant to all ALS chemical groups and five populations are cross-resistant to the PROTOX inhibitors tested. The resistance to ALS inhibitors on the EPHHL biotypes evaluated is attributed to the lower sensitivity of the herbicide target enzyme. The activity of all antioxidant enzymes, both on the resistant and susceptible biotypes, is dependent of the herbicide and on the dose used and can be one of the mechanisms of resistance to PROTOX inhibitors. The biotypes of EPHHL resistant to ALS-inhibiting herbicides remain in the area even after long-term observation of resistance. The resistance to PROTOX inhibitors also remains in areas, but less frequently.

Les microalgues, qui sont à la base des réseaux trophiques aquatiques, peuvent être la cibleindirecte des herbicides provenant des usages agricoles et urbains. Elles sont également en interaction avecd’autres éléments de leur environnement comme la matière organique dissoute (MOD) naturelle, ellemêmesusceptible d’interagir avec les herbicides. Cette thèse a visé à étudier, en milieu contrôlé, l’influencede la MOD naturelle sur la toxicité d’herbicides vis-à-vis de microalgues en cultures monospécifiques nonaxéniques. Ont été considérés de la MOD naturelle d’eau douce et marine, trois herbicides (irgarol, diuronet S-métolachlore) seuls et en mélange, deux espèces de microalgues dulçaquicoles (Gomphonema gracileet Sphaerellopsis sp.) et deux espèces marines (Chaetoceros calcitrans et Tetraselmis suecica). Les effetsont été déterminés sur la croissance, l’efficacité photosynthétique et le contenu relatif en lipides desmicroalgues. En parallèle, l’environnement chimique a été caractérisé en suivant l’évolution de lacomposition et des propriétés de la MOD, ainsi que des concentrations d’herbicides et de leurs métabolites.Les résultats de ces travaux, qui considèrent pour la première fois la MOD naturelle dans sa globalité eninteraction avec des microalgues et des herbicides, démontrent le rôle clé joué par la MOD sur (i) lastimulation de la croissance des quatre espèces de microalgues (et en retour la modification de la MOD parcelles-ci), (ii) la modulation de la toxicité des herbicides et suggèrent (iii) la capacité de Sphaerellopsis sp.et/ou de ses bactéries associées de biodégrader le diuron. / Microalgae are at the basis of aquatic food webs and may be the indirect target of herbicidesfrom agricultural and urban uses. They also interact with other compounds from their environment such asnatural dissolved organic matter (DOM), which can itself interact with herbicides. This thesis aimed tostudy, in laboratory controlled conditions, the influence of natural DOM on herbicide toxicity to microalgaeby using monospecific, non-axenic cultures. The experiments included: natural freshwater and marineDOM, three herbicides (irgarol, diuron and S-metolachlor) singly and in mixtures, two freshwatermicroalgae (Gomphonema gracile and Sphaerellopsis sp.) and two marine microalgae (Chaetoceroscalcitrans and Tetraselmis suecica). Effects were evaluated on microalgae growth, photosyntheticefficiency and relative lipid content. At the same time, changes in chemical environment over theexperiments were measured through DOM composition and properties, as well as the concentrations inherbicides and their metabolites. The results of this work, which consider for the first time natural DOM asa whole, interacting with microalgae, their associated bacteria and herbicides, demonstrate the key roleplayed by DOM in (i) the growth stimulation of four microalgae (and in return the DOM changes inducedby microalgae), (ii) the modulation of herbicide toxicity and suggest (iii) the ability of Sphaerellopsis sp.and/or its associated bacteria to biodegrade diuron in non-axenic conditions.

Résumé : La Bretagne (France) est une région agricole où les polluants émergeants sont très susceptibles d’atteindre les eaux de surfaces. La surveillance institutionnelle montre que les sous-produits d’herbicides sont la principale pollution des eaux de surface, dans une région où 80 % des eaux potables sont produites à partir de ressources superficielles. Le comportement dans l’environnement des sous-produits d’herbicides est mal connu et, pour certains d’entre eux, les contributions de leurs différentes sources font toujours débat. Dans l’est de la Bretagne, le bassin versant de la Vilaine (10 500 km²) est d’un grand intérêt pour la recherche, car il abrite une importante usine de potabilisation (100 000 m3/j) à son extrême aval. Dans ce contexte, cette étude vise à (i) cartographier le bassin versant, (ii) évaluer la contamination et ses variations spatiales et saisonnières, (iii) comprendre les conditions favorables à l’export vers les eaux de surface, (iv) étudier les sources et le devenir de l’AMPA (acide aminométhyl phosphonique) dans les eaux usées, (v) explorer le procédé d’ozonation pour un sous-produit récalcitrant aux traitements de l’eau potable. Cette thèse consiste en trois chapitres : une revue de la littérature sur l’occurrence et le devenir des herbicides et leurs sous-produits dans les eaux de surface, eaux usées, et eau potable; le matériel et méthodes incluant, la sélection des composés d’intérêt, la stratégie d’échantillonnage, la description des méthodes d’analyses et d’assurance qualité, les outils statistiques; les résultats d’occurrence et de comportement des sous-produits d’herbicides dans les différentes eaux étudiées. Ces travaux se concluent sur un contexte plus large avec des perspectives pour acquérir une meilleure compréhension des sources et des facteurs influençant l’occurence des sous-produits d’herbicides dans les différentes eaux, dans le but d’améliorer la qualité des ressources. / Abstract : Brittany (France) is an agricultural region, where emerging pollutants are highly at risk to reach surface waters. Legal monitoring shows that herbicides metabolites are the main pollution of surface waters, in a region where 80 % of drinking water is produced with surface waters. The environmental behavior of herbicides metabolites is badly known and, for some of them, the contributions of their different sources are still debated. In east Britany, the Vilaine watershed (10 500 km²) is of great research interest, as a large drinking water treatment plant (100 000 m3/day) is located at the extreme downstream of it. In this context, this study aims to (i) map the watershed, (ii) evaluate the contamination and its spatial and seasonal variations, (iii) understand the favoring conditions resulting in metabolites export towards surface water, (iv) study sources and fate of AMPA (aminomethylphosphonic acid) in wastewaters, (v) explore ozonation treatment of a resistant metabolite in drinking water This thesis consists of three chapters: a review of the literature on herbicides and their metabolites occurrence and fate in surface waters, wastewaters, and drinking water; the materials and methods including, selection of compounds of interest, sampling strategy, description of the methods of analysis and quality assurance, statistical tools; the results of herbicides metabolites occurrences and behavior in the different waters studied. This work concludes on a broader context by providing perspectives to gain a better understanding of the sources and the factors influencing herbicides metabolites occurrences in the different waters, in order to improve the quality of water resources.