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A soil climate parameterization is designed for peatland environments in the Canadian Land Surface Scheme (CLASS). Three wetland soil classes account for the variation in the hydraulic characteristics of organic soils. Saturated hydraulic conductivity varies from a median of 1.0 x 10-7 m/s in deeply humidified sapric peat to 2.8 x 10-4 m/s in relatively undecomposed fibric peat. Average pore volume fraction ranges from 0.83 to 0.93. Parameters are derived for the soil moisture characteristic curves of fibric, hemic and sapric peat, using the Campbell (1974) equation employed in CLASS, and the van Genuchten (1980) formulation. Validation of modelled water table depth and peat temperature is performed for a fen in northern Quebec and a bog in north-central Minnesota. The new parameterization results in more realistic simulation than the previous version of CLASS, which was constrained to using mineral soil properties to approximate those of organic soils. / Two approaches are used to model methane emissions from northern peatlands using the new soil climate parameterization in CLASS. In the first module, the multiple regression equation of Dise et al. (1993) is used to simulate daily methane emissions from water table depth and peat temperature. In the process-based module, methane flux is divided into its component parts: plant transport, diffusion and ebullition. Each of these transport mechanisms is determined by methane concentrations, which are calculated from a series of processes related to peat temperature, water table level and rooting depth. The daily methane emissions predicted by the two models are similar and correlate reasonably with observations from a bog in north-central Minnesota.

En période d'exploitation minière, le cycle de surface des métaux est perturbé. L’analyse des carottes de sédiments lacustres démontre que le cycle géochimique de surface de la région de Schefferville a été perturbé durant la période de l’exploitation minière, et que le régime naturel pré-industriel n’est toujours pas atteint plus de 30 ans après la fin des activités minières. L’analyse des lichens épiphytes démontre que la ville de Schefferville et les activités anthropiques liées à l’exploitation minière relâchent du Pb dans l’atmosphère. La valeur moyenne ²⁰⁶Pb/²⁰⁷Pb des lichens épiphytes est de 1.153 et correspond à la valeur des émissions atmosphériques canadiennes provenant des industries (²⁰⁶Pb/²⁰⁷Pb = 1.150; Carignan et Gariépy, 1995). Les analyses isotopiques en Pb du minerai et déblais minier démontrent que le Pb retrouvé en période minière dans les sédiments des lacs Oksana et Dauriat pourrait provenir du minerai. Quatre sources de sédimentations ont été identifiées durant les différentes périodes minières (pré-mine, mine et post mine) dans deux lacs de la région.

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A glance at a large scale map of Labrador-Ungava brings to the forefront the fact that a myriad of lakes abound in the area. Schefferville, Quebec, the site of the McGill Sub-Arctic Research Laboratory and of the field work included in this thesis, is in an extremely advantageous location for the study of lakes, both large and small, for besides being in a formerly glaciated area, it is located on folded sedimentaries surrounded by the Canadian Shield. [...]