No description available.

This thesis reports a series of experiments investigating some aspects of seasonal C and nutrient cycling and microbial community responses in an alpine heathland under three environmental pressures: N deposition represented by N additions at four levels (0, 10, 20, 50 kg N ha^-1 yr^-1), climate change simulated by open top chambers (OTCs) and accidental burning (one low intensity fire event that occurred in autumn 1999). The Culardoch experimental site was used, which is located on an alpine heathland in the Eastern Cairngorms mountains, Scotland. The responses studied were related to litter decomposition dynamics, soil processes and the soil microbial community. Mass loss and nutrient status during decomposition of litter from the plots (“native”) and collected outside the plots (“standard”) were studied. Litter decomposition was not affected significantly by the treatments. Despite the decrease in initial C:N ratio by N additions, this treatment affected only phosphomonoesterase activity and a trend for increasing glucosidase and xylosidase activity with increasing N additions was seen. OTC impacts were limited to effects on P cycling in “native” decomposing litter in the later stages of decomposition and more P was accumulated in litter from the plots with the OTCs. Burning affected N cycling in “native” decomposing litter (more N was accumulated in litter incubated in the burnt plots) and mass loss, C, N and P content in “standard” litter. Increased cellulolytic activity was observed in litter from the burnt plots. Those changes were attributed to shifts in the bacterial and fungal communities due to burning and warming treatments, while N additions had only a minor effect on microbial community structure. Decomposition phase had the greatest effect on microbial community structure suggesting that a succession of communities occurred during decomposition. One of the most important findings was the lack of interactive effects among the three main treatments, indicating that they act independently on particular components of the ecosystem.

La mer est un moyen important de transport et du commerce international surtout le transport des produits pétroliers.Mais le transport maritime surtout le transport des hydrocarbures ne peut pas se concevoir sans l'intervention de risques de pollution pétrolière.Certaines zones comme la mer méditerranée sont exposées au trafic maritime très dense qui menace leurs écosystèmes. La mer méditerranée est une route importante pour le transport maritime et elle est un espace de transite.Mais le trafic maritime est une des principales causes de pollutions pétrolières de la mer méditerranée.Cette pollution des navires pourra être de deux types. Il pourra s'agir d'une pollution accidentelle ou d'une pollution opérationnelle.Heureusement la communauté internationale a adopté des règles juridiques pour la répression et la prévention contre la pollution pétrolière provenant des navires. Du fait de sa spécificité, la Méditerranée bénéficiera d'une règlementation particulière.Mais malheureusement il existe actuellement une hétérogénéité entre les pays Méditerranéens dans la mise en œuvre des normes internationales et régionales pertinentes. Cette hétérogénéité est attribuée à deux raisons :- Le régime international et régional contient des lacunes juridiques qui réduisent de son efficacité ;- La géopolitique de la mer méditerranée qui se traduit par l'inégalité économique et technologique entre les pays du Nord riches et les pays du Sud pauvres. / The sea is an important means of international trade and transportation especially the transportation of petroleum products.in fact, the maritime transport of hydrocarbons may in many cases lead to the risk of oil pollution.Some areas like the Mediterranean Sea are exposed to traffic that threatens their very dense ecosystems. The Mediterranean is an important route for shipping and it is a place of transit.But shipping is a major cause of oil pollution in the Mediterranean Sea. This pollution may be of two types. It may be a incident pollution or operational pollution.Fortunately, the international community adopted legal rules for preventing oil pollution from ships. Because of its specificity, the Mediterranean will enjoy a special regulation.But unfortunately there is a current heterogeneity among Mediterranean countries concerning the implementation of relevant international and regional standards. This heterogeneity is attributed to two main reasons:First, the plan may contain regional and international legal shortcomings that reduce its effectiveness.Second, the Geopolitics of the Mediterranean Sea that lead to technological and economic inequality between the rich northern countries and poor southern countries.

No description available.

No description available.

Semi-natural upland plant communities in the U.K. characterised by calcifugous grasslands and montane dwarf shrub communities, with low N requirements, are thought to be particularly vulnerable to the effects of N pollution. N deposition can be enhanced at high altitude sites <I>via</I> cloud droplet deposition and the seeder-feeder effect and the consequences of this for upland vegetation were investigated. Sampling of a range of upland plant species on altitudinal transacts at sites of known N deposition showed that the foliar N concentration increased with altitude and appeared to reflect the enhancement of N deposition with altitude at these sites. Transplant experiments with <I>Nardus stricta</I> in pots and turves showed that although this species reflected N deposition to some extent, the relationship was modified by temperature. This should be taken into account in any attempt to biomonitor N deposition using higher plants. A two year experiment in which upland plant species were misted with N at a rate typical of more polluted sites in the U.K. (60 kg N ha^-1 yr^-1) produced increased root and shoot tissue N concentrations in all species and differential effects on growth and nutrient allocation, and flowering. The dwarf shrubs <I>Vaccinium vitis-idaea</I> and <I>Erica cinerea</I> showed a decrease in root:shoot ratio as a consequence of increased shoot growth, as did the sedge <I>Eriophorum vaginatum</I>, but in the grass <I>Nardus stricta</I> both root and shoot growth were stimulated with the result that there was no change in root:shoot ratio. The magnitude of the response of foliar N concentration to N deposition was species specific and greatest in slow growing species, such as dwarf shrubs, which showed preferential allocation of N to the shoots.

In this study, the amphipod Corophium volutator and the polychaete Arenicola marina were evaluated as test organisms for use in sediment toxicity tests by adapting standard protocols developed by the EPA/COE and Thain et al. (1994) respectively for conducting 10-day sediment toxicity tests. Although these species have been used to assess the toxicity of marine and estuarine sediments, the detailed ecotoxicologies of these animals are not well documented. In particular, the effects of specific contaminants of known concentrations on this bioassay are not known. Here, I report several experiments carried out using clean intertidal sediment contaminated with the heavy metals copper, zinc and cadmium, and employing the Corophium and the Arenicola bioassay protocol. Concentrations of copper, zinc and cadmium were determined in tissues of Corophium exposed for 4 and 10 days to contaminated sediment using four protocols to allow for any material present in the gut. Significant differences in metal concentrations occurred between the protocols where gut contents were removed and those where they were left intact. These findings have implications for the way in which analyses of metal burdens are carried out for invertebrates in ecotoxicological work. Corophium survival in seawater with dissolved copper, zinc and cadmium was higher in the presence of sediment than without sediment, although the concentrations of these metals in Corophium tissues were the same in both cases. Bioconcentration factors (BCF) were inversely related to seawater concentrations of copper, zinc and cadium, with the lowest exposure concentration, (0.1 mg l-1 for both copper and zinc, 0.01 mg l-1 cadmium) having the highest BCF. Both live amphipods and those that had died accumulated copper, zinc and cadmium in their bodies during the bioassay, and bioconcentration factors were always higher for dead than for living amphipods for each metal.

No description available.

Dans le cadre d'une gestion rationnelle des ressources en eau souterraine, il est nécessaire, pour comprendre leur fonctionnement, d'intégrer la composante «eau de surface» et ses transferts superficiels liés à la topographie. La préservation de la qualité de cette eau passe donc par la prise en compte des paramètres intrinsèques et extrinsèques du bassin d'alimentation de la nappe. Dans un premier temps, sur la base de travaux antérieurs réalisés au sein du Laboratoire de Mécanique de Lille (L.M.L., U.M.R. 8107), nous avons développé une méthodologie s'appuyant sur : -l'hydrologie du ou des bassins versants ruraux, -la vulnérabilité à une pollution diffuse de la nappe sous-jacente, -l'activité anthropique ou naturelle de surface, -les phénomènes érosifs affectant le bassin versant et les transferts de molécules qui en découlent. Dans un deuxième temps, nous avons appliqué ces modèles à l'étude d'un aquifère crayeux du bassin Artois Picardie alimentant la galerie captante du village côtier de Wissant (Pas de Calais, France). Ceci nous a permis de tester et de choisir des modélisations adaptées au contexte typologique de ce massif crétacé caractéristique de la région. Ces méthodes ont ensuite été combinées à l'aide d'un SIG afin de représenter la répartition spatiale des écoulements préférentiels, leur lien avec l'érosion et les zones d'accumulation et d'infiltration potentielles vers la nappe. Ce travail apporte des éléments de réponse à la question: «les pertes en sol des bassins versants ruraux ont elles un impact significatif sur la vulnérabilité de la nappe phréatique sous jacente ?». De plus, il met en évidence l'importance de la prise en compte des paramètres géomorphologiques et pédologiques dans l'élaboration d'une stratégie de protection des nappes d'eau souterraine, notamment en ce qui concerne le positionnement des flux polluants dans les modèles mathématiques de simulation, outils d'aide à la décision en matière de gestion optimisée des nappes. Cette méthodologie a été utilisée dans le cadre d'une étude pluridisciplinaire des ressources souterraines en eau alimentant la ville de Calais (Pas de Calais, France). La modification de l'indice de vulnérabilité DRASTIC par intégration du facteur d'atténuation (Af) des molécules polluantes a été testé. La réponse de ce nouvel indice a permis de dresser à l'aide d'un SIG une cartographie plus précise de la vulnérabilité de la nappe aux produits phytosanitaires. Sur le bassin de Guînes, ce modèle a été employé pour quatre molécules : le Prosulfuron, l' AMPA, l' Atrazine et la DEA. / To manage rationnally groundwater ressources, it is necessary to take into account the "surface-water" component and the slight transfers linked ta topography. The preservation of the quality of this water relies on the knowledge of both the inner and outer components of the groundwater watershed area. On the basis of previous works achieved within the Lille Mechanichs Laboratory (LML, UMR 8107), we have developed a methodology based on : -the rural watershed hydrology, -the vulnerability linked to a diffuse pollution of the underlying groundwater, -the surface anthropogenic and natural activity, -the erosion phenomena in the watershed and the consecutive molecule transfers. ln a second time, we have applied these models to the Artois Picardie basin (North of France) chalky aquifer wich supplies the coastal village of Wissant. This allowed us to test and select the models best suitable for the typology of the cretaceous characteristic area. These methods were then combined with a GIS to display the spatial distribution of preferential flows, their connection to erosion and the areas where they pile up and can potentialy infiltrate the groundwater. This work partially answers the question : do the soil losses of rural catching areas have a negative impact on the vulnerability of the groundwater? Moreover it stresser how important it is to take into account the geomorpholgical and soil parameters when setting up a strategy of underground ressources protection. This is particularly true for the positioning of polluting flows in mathematical simulation models which constitute a real decision tool concerning the optimized management of groundwaters. This methodology has been used too in a multidisciplinary study on underground water ressources supplying the city of Calais (Pas de Calais). The DRASTIC index modification by the integration of the attenuation factor Af for pesticide has been used. This new index shows a more accurate groundwater vulnerability to pollution by pesticide on the maps. This vulnerability have been studied on the chalk aquifer of Guînes hills with four molecules : Prosulfuron, AMPA, Atrazine and DEA.

The occurrence of hydrogen sulphide in the environment, the reasons for concern about the levels which may be present, particularly on off-shore installations, and methods for determining the gas in air are reviewed. The original aim of this project was to explain the reasons for the variations in the levels of naturally occurring hydrogen sulphide over the estuary of the Don at Aberdeen. The monitoring work required a reliable method: as the published methods were all problematical, much effort was expended in improving the Ethylene Blue method and investigating the range of trapping solutions. The final optimised method has been published (Analyst 1988, 113, 1635). An alternative method for standardising H2S in air gas mixes has also been developed and used on commercial samples. Microbiological studies have shown that sulphate-reducing bacteria were not present in the sediments of the Don estuary in 1988 (but were present in sediments from the Forth estuary) and further, that the Don sediments would not support growth of SRB's, which in part explains why there has been effectively no release of H2S from the estuary in recent years. Attempts have been made to correlate the H2S emission events with changes in river water quality over the last ten years, but no obvious clues have become evident.