Biomass energy is currently the largest renewable contributor to global energy supply and there is increasing demand for bioenergy feedstock. Consequently, the production of purpose-grown woody bioenergy crops, such as short rotation coppice (SRC) willow, is expected to proliferate. Although the economic and environmental benefits associated with SRC willow production are well documented, systematic assessments of nutrient cycling within these plantations are rare. The objective of this study was to examine biomass production and biogeochemical cycling of nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca), and magnesium (Mg) during an initial four-year rotation of six willow varieties grown at four plantations along a 500 km north-south pedoclimatic gradient within Saskatchewan, Canada. Nutrient budgets were also calculated after quantifying various nutrient inputs (e.g., atmospheric deposition, soil mineral weathering, and organic matter mineralization), outputs (e.g., above- and below-ground biomass, leaching, and denitrification), and transfers (e.g., canopy exchange, leaf litter decomposition, and fine root turnover) affecting the plant available soil nutrient pool. Total stem, leaf litter, and below-ground (primarily fine roots) biomass production after four years averaged 19.0, 7.1, and 12.5 Mg ha-1, respectively, with corresponding soil nutrient budget deficits of 17, 39, 112, 271, and 74 kg ha-1 of N, P, K, Ca, and Mg, respectively, but a soil S surplus of 60 kg ha-1. Despite willow’s relatively low nutrient-demanding nature, negligible leaching and denitrification losses, and substantial nutrient cycling from leaf litter, the nutrient export in harvested biomass over multiple rotations will require soil nutrient amendments, particularly N and P, to maintain plantation productivity. Given the apparent eventual need for supplemental fertility to support adequate willow growth over the 22-yr plantation life span, the fate of broadcast 15N-labelled fertilizer was also examined. Though the willow accumulated less than ⅓ of the applied fertilizer N after one year, the majority of the residual fertilizer N (51%) remained available for willow uptake in subsequent years. Further research is needed to track the fate of applied fertilizers over multiple rotations to better understand fertilizer dynamics for optimizing SRC willow agronomy; thus helping to promote its viability as a biomass energy feedstock option.

Que ce soit par rejets chroniques ou accidentels, l’impact d’une installation nucléaire sur l'environnement dépend essentiellement des transferts atmosphériques qui, comme le montre l'accident de Fukushima, impacts sur l’environnement et les populations. Ce travail s’intéresse à la caractérisation et à la modélisation du dépôt sec des aérosols submicroniques sur des surfaces liquides en mouvement telles que des rivières. Compte tenu de l’inexistence de données sur le dépôt sec des aérosols submicroniques sur une surface liquide en mouvement, la démarche s’est appuyée sur : 1) l’acquisition expérimentale de vitesses de dépôt et 2) l’analyse et l’interprétation des résultats au moyen d’un travail de modélisation. Les expérimentations de dépôts ont été réalisées avec des aérosols d’uranine injectés dans la maquette de la soufflerie IOA-IRPHE. Ces expérimentations ont permis d’obtenir de nombreuses vitesses de dépôt sec pour différentes configurations caractérisées en fonction des conditions de vent, de courant, d’ambiance, de déformations de la surface liquide (mesures des vagues) et de distribution granulométrique des aérosols injectés. La partie modélisation a consisté à adapter le modèle à résistance de Slinn et Slinn (1980). Les principales adaptations apportées par ce travail ont consisté à prendre spécifiquement en compte les différentes classes de particules du spectre granulométrique du champ aérosolique, à évaluer les évolutions de ce spectre en fonction des mécanismes d’hygroscopicité et d’agrégation et à intégrer les mécanismes de diffusiophorèse et de thermophorèse. / Whether by chronic or accidental releases, the impact of a nuclear installation on the environment mainly depends on atmospheric transfers; and as the accidents at Chernobyl and Fukushima show, affect the contamination of surfaces and impacts on the environment and the population. This work focuses on the characterization and modeling of dry deposition of submicronic aerosols on liquid surfaces in motion such as rivers. The evaluation of dry deposition is based on the estimation of flux modeling as the product of particle concentration and deposition velocity. Due to the lack of data on the dry deposition of submicronic aerosols on a liquid surface in motion, the approach was based on two axes: 1) the acquisition of experimental deposition velocities and 2) the analysis and interpretation of results through modeling. The experiments were performed with uranine aerosols released into the IOA-IRPHE wind tunnel. These experiments have given many dry deposition velocities for different configurations characterized according to wind, current, ambient temperature and relative humidity, the liquid surface deformations (measured significant wave height) and size distribution of aerosols released. The modeling part was to adapt the model to resistance. Slinn and Slinn (1980). The main adjustments made by this work have been to take specific account of the different classes of particle size distribution, the spectrum variation as a function of hygroscopicity, and mechanisms of aggregation. It is integrated mechanisms of diffusiophoresis and thermophoresis, respectively produced by the evaporation of water and the temperature gradient at the air-water interface.

No description available.