Le travail de cette thèse a consisté à développer des microbiocapteurs de type ISFET (Ion Sensitive Field Effect Transistor) et conductimétrique en utilisant l'enzyme tyrosinase pour la détection de pesticides dans l'eau. Ces deux types de capteurs ont été mis au point à l'Institut International de Formation de Science en Matériaux (ITIMS), Viet Nam. En particulier, les étapes de diffusion de dopants ont été réalisées par la technique Spin On Glass (SOG). La biofonctionnalisation de ces capteurs a été réalisée par immobilisation de l'enzyme tyrosinase avec de la bovine sérum albumine (BSA) en présence de vapeur de glutaraldéhyde. Le temps de contact avec le glutaraldéhyde, la charge en enzyme, le pH, la nature du substrat, le temps pour chaque mesure... ont été optimisé afin d'obtenir les meilleurs caractéristiques analytiques possibles. Ces capteurs nous ont permis de détecter en phase aqueuse des dérivés phénoliques ainsi que des pesticides de type diuron et atrazine. La limite de détection est de 2,15 ppb pour l'atrazine et 2,33 ppb pour le diuron, le temps de réponse est de 1 à 5 minutes, l'activité enzymatique reste de 90% après 23 jours dans un tampon à 4°C et la dérive est de 5%.

Ce travail de recherche s'inscrit dans le contexte de contamination des sols par les pesticides utilisés en agriculture. Cette problématique est un enjeu majeur et actuel puisque l'étendue spatio-temporelle de la contamination est méconnue. Il s'agit donc ici de mieux comprendre la dynamique des herbicides dans les écosystèmes pour mieux en évaluer les risques a priori et plus précisément de savoir dans quelle mesure et par quels mécanismes les organismes édaphiques régulent leurs dynamiques physiques et chimiques. Deux hypothèses alternatives ont été testées avec la molécule herbicide modèle, l'atrazine : i) la macrofaune lombricienne contribue à la dégradation partielle ou totale de l'atrazine en stimulant l'activité de la microflore dégradante et ii) la macrofaune lombricienne favorise la liaison de l'atrazine avec les complexes argilo-humiques du sol, au sein de microsites favorisant la rétention et la rémanence de l'herbicide. Des expérimentations en présence et en absence de Lumbricus terrestris et Aporrectodea caliginosa ont été effectuées à différentes échelles spatiales et temporelles, avec de l'atrazine-14C. S'agissant du rôle de la macrofaune lombricienne, les résultats expérimentaux obtenus ont montré que : • l'ingestion du sol par la macrofaune lombricienne favorise l'adsorption de l'atrazine et conduit à un redistribution des quantités d'atrazine et de ses résidus liés dans les biostructures (avec dans l'ordre : parois de galeries - déjections excrétées dans les galeries – déjections en surface ou turricules – contenus intestinaux ou endentères) par rapport au sol non ingéré et due à un enrichissement en carbone organique conjugué à une plus forte microporosité. • inversement, la minéralisation de l'atrazine n'est pas stimulée voire ralentie en présence de vers. C'est le passage du sol dans le tractus digestif, au cours duquel la structuration des communautés bactériennes initiales du sol est modifiée, qui limite la dégradation totale de l'atrazine par voie microbienne. • une diminution significative du potentiel génétique dégradant (gènes atz) consécutive à l'ingestion a été mise en évidence, suggérant une forte déplétion de la population bactérienne dégradante Pseudomonas sp. ADP. De ces résultats originaux, il est conclu que l'activité de la macrofaune lombricienne dans les sols tendrait à augmenter le temps de résidence du polluant et donc sa rémanence mais s'opposerait à son élimination par biodégradation naturelle par les bactéries.

The overall objective of this thesis is to better understand and assess pesticide leaching at the regional scale, using both the analysis of monitoring data and spatially distributed modelling. Atrazine contamination of the Brusselian aquifer (central Belgium) is poorly understood. Considerable uncertainty surrounds whether the pollution is agricultural or non-agricultural in origin. The spatial and temporal covariance of atrazine concentrations was studied by fitting semivariogram models to monitoring data. Correlation ranges were found to be 600 metres and 600-700 days. A non-parametric one-way ANOVA found a strong relationship between mean concentrations and land use, whilst other environmental variables were found to be less important. Higher levels of pollution were detected in areas dominated by urban land use suggesting that atrazine residues in groundwater resulted from non-agricultural applications. Modelling pesticide leaching at the regional scale (Dyle catchment) was used to assess groundwater vulnerability. Different approaches to process soil information were tested with both a linear (modified Attenuation Factor) and a non-linear (GeoPEARL) leaching model. The CI (calculate first, interpolate later) and IC (interpolate first, calculate later) approaches were identical for the linear model, but differences in the amount of leaching were found for the non-linear model. The CI approach would be expected to give better results than IC, but the CA (calculate alone) approach is probably the best method if no spatial output is required. Finally, a methodology was developed to quantify the uncertainty arising from the spatial variability of non-georeferenced parameters (i.e. those assumed to be spatially constant in deterministic simulations). A Monte Carlo analysis of atrazine leaching was performed with six pesticide and soil properties as uncertain inputs. Spatial variability of non-georeferenced parameters had a significant influence on the amount of simulated leaching. In the stochastic simulation, concentrations exist above the regulatory level of 0.1 µg/L, while virtually no leaching occurred in the deterministic simulation. Including the spatial variability of substance parameters (half-life, sorption coefficient...) would have significant consequences for future registration policies, especially if risk assessments are implemented in a spatially distributed way.

The synthesis, characterization and application of dendrimers on solid supports are described. Melamine-based dendrimers are incorporated on clay minerals and silica gel. The hybrid materials are characterized using a variety of analytical techniques including thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). The first chapter gives an overview of the two main methods, convergent and divergent, for the synthesis of dendrimers. It also describes the synthesis of melamine-based dendrimers and their advantages over conventional dendrimers. Synthetic strategies and applications of dendrimers at surfaces are discussed. The preparation of organoclay materials containing dendritic surfactants is presented in the second chapter. The morphology of these organoclays is studied by X-ray powder diffraction (XPD). A new type of morphology is observed when large dendritic surfactants are incorporated onto the clay. This new morphology is described as frustrated intercalation. The ability of the dendritic organoclay composites to recognize small organic molecules in water is presented in the third chapter. Atrazine, a commonly used herbicide, is used as a model compound. Structure-activity relationship studies were conducted in order to gain some insight on the recognition and sequestration mechanisms. In the fourth chapter, reactive resins are evaluated for the covalent sequestration of monochlorotriazines from organic and aqueous solutions. The sequestration is monitored spectrophotometrically and using liquid chromatography coupled to a mass spectrometer (LC-MS). 1H NMR spectroscopy and MS are used to identify the covalent adducts formed between the monochlorotriazines and the resins. The efficiency of the resin is compared to several types of charcoal using aqueous solutions of atrazine. The final chapter describes the attachment of melamine-based dendrimers onto silica gels. Dendrimers are incorporated to the silica gel surface using two synthetic strategies, the stepwise growth strategy (SGS) and the "attach-to" strategy (ATS). These composites are also evaluated for their ability to remove atrazine from aqueous solutions.

The presence of micropollutants, particularly pesticides, in surface waters across Canada has been of concern not only for their environmental impact, but also for their potential effects on human health and recalcitrant nature to conventional water treatment methods. Although ozone has been mainly applied for disinfection of drinking water, oxidation of trace organics by ozonation has been considered potentially effective. In an effort to meet increasingly stringent drinking water regulations, different solid catalysts have been used to enhance the removal of water contaminants by ozonation. In spite of the increasing number of data demonstrating the effectiveness of heterogeneous catalytic ozonation, the influence of different factors on the efficiency of micropollutants oxidation is still unclear.<p> In the present work, application of three solid catalysts in ozonation of two model micropollutants in pure water was examined using a laboratory-scale reaction system over a range of operating conditions. The three catalysts investigated were activated carbon, alumina, and perfluorooctyl alumina, and the two model micropollutants were the pesticides atrazine and 2,4-dichlorophenoxyactic acid. The effects of solution pH, presence of a radical scavenger, pesticide adsorption on catalyst, and catalyst dose on micropollutant removal were investigated. Solution pH was found to significantly influence the catalyst ability to decompose ozone into free hydroxyl radicals. The effect of these free radicals was markedly inhibited by the radical scavenger resulting in a negative impact on pesticides degradation. In general, the removal rate of pesticides was found to increase with increasing doses of catalyst.<p> In the ozonation process in the presence of activated carbon, atrazine removal rates increased four and two times when using a catalyst dose of 0.5 g L-1 at pH 3 and 7, respectively, whereas observed reaction rates for 2,4-D increased over 5 times in the presence of 1 × 10-4 M tert-butyl alcohol at pH 3. In the ozonation system catalyzed by 8 g L-1 alumina, the observed reaction rate constant of atrazine removal notably improved at neutral pH by doubling the micropollutant removal rate. For the pesticide 2,4-D in the presence of 1 × 10-4 M tert-butyl alcohol at pH 5, the observed removal rate was over ten times higher than that for the non-catalytic ozonation process using also using a catalyst dose of 8 g L-1. Modification of alumina to produce perfluorooctyl alumina resulted in a material able to significantly adsorb atrazine, while not exhibiting affinity for adsorption of 2,4-D. In spite of its adsorptive properties, perfluorooctyl alumina was found to enhance neither molecular ozone reactions nor ozone decomposition into hydroxyl radicals. Thus, the observed removal rates for atrazine and 2,4-D by ozonation in the presence of perfluorooctyl alumina did not increase significantly.

The presence of micropollutants, particularly pesticides, in surface waters across Canada has been of concern not only for their environmental impact, but also for their potential effects on human health and recalcitrant nature to conventional water treatment methods. Although ozone has been mainly applied for disinfection of drinking water, oxidation of trace organics by ozonation has been considered potentially effective. In an effort to meet increasingly stringent drinking water regulations, different solid catalysts have been used to enhance the removal of water contaminants by ozonation. In spite of the increasing number of data demonstrating the effectiveness of heterogeneous catalytic ozonation, the influence of different factors on the efficiency of micropollutants oxidation is still unclear.<p> In the present work, application of three solid catalysts in ozonation of two model micropollutants in pure water was examined using a laboratory-scale reaction system over a range of operating conditions. The three catalysts investigated were activated carbon, alumina, and perfluorooctyl alumina, and the two model micropollutants were the pesticides atrazine and 2,4-dichlorophenoxyactic acid. The effects of solution pH, presence of a radical scavenger, pesticide adsorption on catalyst, and catalyst dose on micropollutant removal were investigated. Solution pH was found to significantly influence the catalyst ability to decompose ozone into free hydroxyl radicals. The effect of these free radicals was markedly inhibited by the radical scavenger resulting in a negative impact on pesticides degradation. In general, the removal rate of pesticides was found to increase with increasing doses of catalyst.<p> In the ozonation process in the presence of activated carbon, atrazine removal rates increased four and two times when using a catalyst dose of 0.5 g L-1 at pH 3 and 7, respectively, whereas observed reaction rates for 2,4-D increased over 5 times in the presence of 1 × 10-4 M tert-butyl alcohol at pH 3. In the ozonation system catalyzed by 8 g L-1 alumina, the observed reaction rate constant of atrazine removal notably improved at neutral pH by doubling the micropollutant removal rate. For the pesticide 2,4-D in the presence of 1 × 10-4 M tert-butyl alcohol at pH 5, the observed removal rate was over ten times higher than that for the non-catalytic ozonation process using also using a catalyst dose of 8 g L-1. Modification of alumina to produce perfluorooctyl alumina resulted in a material able to significantly adsorb atrazine, while not exhibiting affinity for adsorption of 2,4-D. In spite of its adsorptive properties, perfluorooctyl alumina was found to enhance neither molecular ozone reactions nor ozone decomposition into hydroxyl radicals. Thus, the observed removal rates for atrazine and 2,4-D by ozonation in the presence of perfluorooctyl alumina did not increase significantly.

The synthesis, characterization and application of dendrimers on solid supports are described. Melamine-based dendrimers are incorporated on clay minerals and silica gel. The hybrid materials are characterized using a variety of analytical techniques including thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). The first chapter gives an overview of the two main methods, convergent and divergent, for the synthesis of dendrimers. It also describes the synthesis of melamine-based dendrimers and their advantages over conventional dendrimers. Synthetic strategies and applications of dendrimers at surfaces are discussed. The preparation of organoclay materials containing dendritic surfactants is presented in the second chapter. The morphology of these organoclays is studied by X-ray powder diffraction (XPD). A new type of morphology is observed when large dendritic surfactants are incorporated onto the clay. This new morphology is described as frustrated intercalation. The ability of the dendritic organoclay composites to recognize small organic molecules in water is presented in the third chapter. Atrazine, a commonly used herbicide, is used as a model compound. Structure-activity relationship studies were conducted in order to gain some insight on the recognition and sequestration mechanisms. In the fourth chapter, reactive resins are evaluated for the covalent sequestration of monochlorotriazines from organic and aqueous solutions. The sequestration is monitored spectrophotometrically and using liquid chromatography coupled to a mass spectrometer (LC-MS). 1H NMR spectroscopy and MS are used to identify the covalent adducts formed between the monochlorotriazines and the resins. The efficiency of the resin is compared to several types of charcoal using aqueous solutions of atrazine. The final chapter describes the attachment of melamine-based dendrimers onto silica gels. Dendrimers are incorporated to the silica gel surface using two synthetic strategies, the stepwise growth strategy (SGS) and the "attach-to" strategy (ATS). These composites are also evaluated for their ability to remove atrazine from aqueous solutions.

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Pesticides are an important component of New Zealand’s primary production sectors. Infestation of pests and diseases can affect crop yield, crop value and damage the country’s export reputation, resulting in economic losses. Repeat applications of pesticides, however, can result in contamination of land and water. Therefore, it is important to understand the fate of pesticides in the environment. Factors which can affect pesticide persistence include soil properties (pH, SOM, CEC), leaching and run-off, volatilisation and co-contamination with heavy metals. Many soils in New Zealand contain high levels of copper from historical applications of copper-based pesticides. Co-contamination of soils may lead to the persistence of some synthetic organic pesticides. An investigation was undertaken to determine the effects of co-contamination with copper on the biodegradation of atrazine and indoxacarb in a New Zealand soil. A Templeton sandy loam soil was spiked with CuSO₄ to achieve concentrations of 0, 100, 250, 500 and 1000 mg kg⁻¹ Cu. The spiked soils were field aged for six months prior to pesticide spiking with either atrazine or indoxacarb. The aged Cu-spiked soils were spiked with either atrazine or indoxacarb at a rate of 2 mg kg⁻¹. A glasshouse study was conducted to determine if copper inhibited the degradation of the pesticides. The pesticide-spiked soils were sampled at the time of spiking (t₀), at the estimated half-lives (t₁) and at twice the estimated half-lives (t₂) of the individual pesticides. The estimated half-lives were based on literature values. The bioavailability and subsequent adverse effects of copper on the soil microbial community was investigated. Total and bioavailable copper concentrations, phosphatase and urease enzyme activities, microbial biomass, and pesticide residue concentrations were all measured in the experimental soil. Methods were developed for the extraction of atrazine, atrazine metabolite and indoxacarb residues from the experimental soil. Total copper concentrations extracted ranged from 4–1060 mg kg⁻¹ in the experimental soils and were consistent throughout the pesticide degradation studies. The bioavailability of copper was a maximum of 2% of the total copper concentration. Bioavailable copper concentrations were positively correlated to total copper (p<0.01). Soil biological properties were investigated to determine the effects of copper on the soil microbial community. Phosphatase and urease enzyme activities, as well as microbial biomass concentrations, were negatively correlated with total copper (p<0.05). Total copper was a better indicator of effects on microorganisms than bioavailable copper. The soil biological properties began showing adverse effects above a total copper concentration of 100 mg kg⁻¹. This concentration also corresponds to New Zealand’s copper limit in biosolids, which is protective of human, plant and microorganism health. Phosphate buffer extraction methods were developed for the analysis of atrazine and indoxacarb residues in the experimental soil by HPLC-UV. Elevated copper concentrations did not inhibit the degradation of atrazine or indoxacarb in the experimental soil. The half-lives of both atrazine (≤19.4 d) and indoxacarb (≤18.8 d) were lower in the spiked experimental soils than the means reported in previous New Zealand and international studies, but were within the reported ranges. This study provided the first data on the fate of indoxacarb in New Zealand. Hydroxyatrazine was the only metabolite detected in the atrazine-spiked experimental soils. Significant differences between the control (Cu-1) and copper levels above 100 mg kg⁻¹ were observed for hydroxyatrazine at t₂. Significant negative correlations were observed between hydroxyatrazine and the microbiomass at t₁ and phosphatase activity at t₂ (p<0.05). These significant relationships suggest that elevated copper concentrations may alter the degradation of this metabolite in the experimental soils due copper toxicity of the soil microbial community. The results of this thesis indicate that elevated levels of copper above 100 mg kg⁻¹ negatively impact the soil microbial community and may reduce the overall health of the soil. Biodegradation is a key mechanism for the degradation of atrazine and indoxacarb in the soil, so it is important that the health of the soil microbial community is maintained. Therefore, it is recommended that atrazine and indoxacarb are only applied to soils with a total copper concentration less than 100 mg kg⁻¹. This will protect the health of the soil microbial community and prevent the potential adverse effects of copper on the degradation of pesticide metabolites in the soil.

Male mating signals convey important mate-quality information to females and are regulated by androgens. Endocrine disrupting compounds (EDCs) are chemicals that interfere with proper hormonal functioning in exposed animals, causing altered hormone levels and resulting in changed reproductive characteristics, including mating signals. Altered signals can have ecological implications by influencing population and community dynamics and evolutionary implications via trans-generational reduction in signal reliability leading to reduced preference and eventual loss of the signal trait. I examined the effects of exposure to environmentally relevant concentrations of atrazine, a widely used herbicide and EDC, on mating signals and behaviors in male guppies, a sexually dimorphic freshwater fish. Guppies were exposed either during adulthood or embryonic development. Prolonged atrazine exposure during adulthood reduced the size of the carotenoid-based ornament, the number of courtship displays performed, and aggression towards competing males. Embryonic exposure did not affect survival to adulthood and the time to develop male-specific morphologies. But there was a trend for smaller genitalia, and the ornament size was significantly increased. Possible increases in immunocompetence as a result of slight estrogenecity may have allowed for greater carotenoid allocation to the ornament. Embryonic exposure also resulted in reduced courtship behavior, forced copulatory attempts and aggression towards competitors; female guppies found these males less attractive. The low dose had the strongest effects with embryonic exposure, indicating the importance of low-dose exposures. These studies highlight the effects of low and environmentally relevant doses of atrazine on mating signals and behaviors in exposed wildlife. A mathematical model was used to understand the evolutionary effects of EDCs on the optimal allocation of carotenoids between ornament and immunocompetence. Animals obtain carotenoids through their diet, and allocate some of this to enhance immune function and the rest to ornaments for mate attraction. The model replicates the disruption of carotenoid-based ornaments as a result of EDC-exposure, and predicts that signal reliability will be reduced. The model simulates an evolutionary shift in the optimal allocation if exposure spanned multiple generations, but signal reliability is not restored. Including additional selective forces like predation further suppresses signal reliability.