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Table of contents
Сhapitre 1. Introduction général
1.1. Contexte de l’étude
1.1.1. La matière organique dans les écosystèmes aquatiques continentaux
1.1.2. Les métaux dans les écosystèmes aquatiques continentaux
1.1.3. Transformation des colloïdes organo-mineraux par des bactéries hétérotrophes dans les eaux des zones boréales
1.1.4. Transformation de la matière organique sous l’action de la lumière du soleil dans les eaux naturelles
1.2. Description de la région
1.2.1. Climat
1.2.2. Rivières, lacs et marécages
1.2.3. Sol et végétation
1.3. Objectifs de l’étude
1.4. Structure de la thèse
Chapitre 2. Transformation of organo-ferric peat colloids by a heterotrophic bacterium
2.1. Résumé
2.2. Abstract
2.3. Introduction
2.4. Materials and Methods
2.4.1. Isolation and culturing of P. saponiphila
2.4.2. Peat leachate preparation
2.4.3. Experimental design
2.4.4. Analytical techniques
2.4.5. Modeling
2.5. Results
2.5.1. Removal of different colloidal fractions in the course of experiments
2.5.2. Partitioning of TE among different size fractions of peat leachate during its interaction with P. saponiphila
2.5.3. Control experiments of DOC and TE release from the biomass and metal adsorption on cell surfaces
2.6. Discussion
2.6.1. General features of DOC and TE biodegradability and adsorption on cell surfaces.
2.6.2. Response of organo-ferric colloids to the presence of bacterial cells
2.6.3. Consequences for biogeochemistry of carbon and trace metals in peat-drained boreal waters
2.7. Conclusions
2.8. Acknowledgements
Chapitre 3. Low biodegradability of dissolved organic matter and trace metal from subarctic waters
3.1. Résumé
3.2 Abstract
3.3. Introduction
3.4. Materials and Methods
3.4.1. Heterotrophic bacteria
3.4.2. Organic substrates of boreal surface waters
3.4.3. Experimental set-up
3.4.4. Analytical techniques
3.4.5. Statistical treatment and thermodynamic modeling
3.5. Results
3.5.1. Evolution of biomass, live cell number, pH, and dissolved carbon
3.5.2. Trace metal concentration change in the presence of bacteria
3.5.3. Metal speciation and saturation degree of solution
3.6. Discussion
3.6.1. DOC and trace element behavior during biodegradation: short-term adsorption and long-term removal via coagulation and assimilation
3.6.2. Heterotrophic bacteria control on carbon and trace metals in boreal organic-rich waters
3.7. Conclusions
3.8. Acknowledgements
Chapitre 4. Dissolved organic matter degradation by sunlight coagulates organo-mineral colloids and produces low-molecular weight fraction of metals in boreal humic waters
4.1. Résumé
4.2. Abstract
4.3. Introduction
4.4. Sampling, materials and methods
4.4.1. Environmental setting
4.4.2. Experimental setup
4.4.3. Sample analysis
4.4.4. Thermodynamic modeling and statistical treatment
4.5. Results
4.5.1. pH, DOC, SUVA, phosphorus and anions in <0.22 μm fraction
4.5.2. Fe, Al and trace element in 0.22 μm fraction during sunlight exposure
4.5.3. Elementary composition of colloids, DOC and TE size fractionation change in the course of photo-degradation
4.6. Discussion
4.6.1. Change of concentration, optical properties and size fractionation of DOC during sunlight exposure
4.6.2. Mechanisms of organo-mineral colloid transformation during irradiation of stream and bog waters
4.6.3. Natural implications
4.7. Concluding remarks
4.8. Acknowledgements
Сhapitre 5. Conclusion général
Bibliographie
