Rivers and streams are increasingly recognised as important components in the global carbon cycle, and act as net sources of CO2 and CH4 to the atmosphere. However, the origins and controls over the fate of these greenhouse gases are still poorly constrained. This thesis firstly explores the production of CO2 and CH4 in the sediment of several rivers over a geological gradient (chalk, sand and clay), to investigate the magnitude and controls on production. It was found that, whilst there are some general patterns due to geology, variables such as organic carbon content are much better predictors of production of CO2 and CH4 and these can vary widely within a single reach. The response of production to temperature was found to be very constant across rivers and in both summer and winter, suggesting a uniform increase in production of both CO2 and CH4 with projected future climate change. However, production of CH4 was much more responsive to temperature change than was CO2, meaning a greater proportion of carbon is mineralized as CH4 under warmer conditions and indicating a positive feedback with global warming. In addition, the amount of CO2 and CH4 out-gassed from the rivers to the atmosphere was measured. It was found that the amount out-gassed could not be explained by local sediment respiration alone: CO2 out-gassing was consistently higher (and CH4 consistently lower) than that produced by the riverbed. Instead, CO2 out-gassing was under hydrological control, and was correlated with rainfall. The source of this was ingress from the surrounding catchment, with higher out-gassing during periods of high rainfall. This strong hydrological controls on CO2 emissions were however modulated by biological processes, as lower emissions were measured during the day than night; and the difference could be accounted for by local in-stream GPP.

In this study, Mg, Sn, Cd, Bi and Sb containing, five binary, three ternary and two quaternary different alloys to be used in a Valve-Regulated Lead-Acid (VRLA) batteries have been studied in terms of their mechanical and electrochemical properties. The investigated properties are hardness, passivity, corrosion rate, hydrogen gassing and the conductivity of the passive film. All electrochemical tests were carried out in 3.75 M H2SO4 solution by using open-circuit potential, anodic polarization, polarization resistance measurement and gas collection techniques. The results showed that while the minimum hardness values were observed in Pb and Pb-Bi alloy, Mg containing alloys have the highest hardness values among all alloys. According to corrosion measurements, lowest icritical value was obtained for Pb, Pb-Bi and Pb-Sn, which reached to passivation region earlier than others. Passive film formation was seen for all specimens. The noble Ecorr value and minimum corrosion rates belonged to Pb and Pb-Mg. Pb-Bi and Pb-Cd have the highest gas evolution rate. Besides, there were not seen much difference in the gassing behavior of Pb-Sn and Pb-Sb alloys. Mg is found to have a superior effect on hydrogen gassing. Addition of Sn, as an alloying element, to lead increases the conductivity of the passivation layer. Mg containing alloys did not show good conductivity characteristic. As a result, Mg containing alloy seemed to have an important role because of the desired hardness, corrosion and, gas evolution behavior. However, conductivity of passivation layer of these alloys came up to be low due to the higher tendency of Mg to oxidation. Even so, Mg seems to be a promising alloying element for lead grid alloys in Valve-Regulated Lead-Acid (VRLA) batteries.

A flux chamber is an effective and recognized means of sampling off gassing surfaces, such as landfills and settling ponds. Because there has been little discussion on the survey patterns used for deploying flux chambers. This thesis looks into developing a scalable survey pattern as part of a flux chamber test methodology that can accurately give a representative sample of the emission components and the emission rate of the entire area of interest. The test methodology evolved out of literature review and experiences of two case studies which are discussed within this thesis.

The first chapter of the thesis deals with the occurrence of gases in the aluminum melt, what are their sources, what is the solubility of hydrogen in the aluminum melt and the formation of gas cavities. The second chapter divides the defects caused or associated with the presence of gases in the casting. They can be bubbles, shrinkage, or diluents. Pore morphology and its influence on mechanical properties are discussed. The third chapter deals with methods of melt degassing, either by vacuuming, bubbling with active or inert gases, or using special methods and preparations. In the fourth chapter methods for determination of hydrogen content in aluminum melt are divided into analytical methods, methods based on Sieverts law and indication methods. The fifth chapter deals with controlled gassing, its objectives and the preparations used for this purpose. The sixth chapter describes the experiment where the influence of the amount of Probat Fluss Micro 100 on the different casting thicknesses and its results were investigated using a test casting.

La prise de conscience des problèmes écologiques liés à l'émission de solvants dans l'atmosphère a<br />provoqué la mise en place d'un cadre législatif auquel les fabricants de peintures ont dû s'adapter.<br />L'évolution vers l'utilisation des peintures en phase aqueuse n'a pu être réalisée sans des aménagements tant au niveau des procédés que des produits. Ainsi, les pigments aluminium mis en oeuvre dans les peintures métallisées, principalement destinées à l'industrie automobile, doivent subir des traitements préalables leur permettant d'éviter des phénomènes de corrosion préjudiciables tant du point de vue esthétique que de la sécurité (dégagement d'hydrogène). Les traitements proposés jusqu'ici (composés phospho-organiques, dérivés du chrome hexavalent) ne sont pas exempts de défauts (toxicité). Cette étude a permis de montrer que l'encapsulation des pigments aluminium dans une coque de PMMA par un procédé dérivé de la polymérisation en émulsion permet d'obtenir des pigments stables en phase aqueuse. De plus, la mise au point d'un nouveau procédé de production , mettant en oeuvre des agents silaniques au cours de l'étape de broyage, permet désormais d'envisager l'élaboration d'un grade universel, i.e. adapté pour les<br />peintures en phase aqueuse et solvant.

Wood pellets have become a solid biomass fuel of choice because they are a standardized product with known quality properties. However, the self-heating and off-gassing tendencies during storage of wood pellets threatens the consistency of the pellets’ quality properties. The aim of this thesis was to increase the body of knowledge towards understanding of the off-gassing of wood pellets. The effects of total wood extractive content and types of extractives in the raw material on off-gassing of wood pellets were investigated through two separate studies. In the first study, the pellets were produced from fresh and pre-treated Scots pine sawdust. The pre-treatments involved storing, extraction and adding additive oils. The second study used synthetic pure cellulose that was pre-treated by adding different additive oils. The pellets were subjected to off-gassing tests under controlled conditions. The results from the first study showed that the total amount of extractives in the raw material has little effect on off-gassing. While gas emissions were reduced for stored and acetone extracted pine pellets, the coefficients of determination (R2) from the linear correlation analysis between off-gassing and the total extractive content of the raw materials were below 0.5 for all the three off-gasses indicating no correlation. The results of cellulose pellets with added additive oils in the second study showed that the off-gassing is highly dependent on the type of extractives in the raw material. The highest mean concentrations of the carbon oxides and methane were recorded from cellulose pellets with added linseed oil. Pellets with added linseed oil had higher off-gas emissions due to the high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. Based on these results, it was concluded that one of the main causes of off-gassing during storage of wood pellets is the α-oxidation of unsaturated fatty acids. The other notable effect was that methane formation is dependent on anaerobic conditions, whereas formation of carbon oxides can occur both under aerobic and anaerobic conditions. / Wood pellets have over the years become a solid biomass fuel of choice for heat and power generation because they are a standardized product with known quality properties. However, the self-heating and off-gassing tendencies of wood pellets threatens the consistency of the quality properties. Self-heating and off-gassing can cause disintegration of the pellets resulting in dry matter losses and reduction in quality properties. Additionally, self-heating may lead to fires while off-gassing of toxic gasses such as carbon monoxide is a human health and environmental hazard. The aim of this thesis was to increase the body of knowledge towards the understanding of off-gassing of wood pellets. The results showed that total amount of extractives in the raw material has little effect on off-gassing. One of the main causes of off-gassing of carbon oxides by wood pellets is the α-oxidation of unsaturated fatty acids and other triglyceride oils that are chemically unstable. The other notable effect was that methane formation is dependent on anaerobic conditions, whereas formation of carbon oxides can occur both under aerobic and anaerobic conditions. / <p>This study was part of the project on secure and well-characterised raw materials and products through innovative adaption of pellets manufacturing processes (SVINPELS, project no 47997–1). This was a collaborative research project between Karlstad University and the Swedish University of Agricultural Sciences, SLU and was funded by the Swedish Energy Agency.</p>

This master thesis will cover the possibility of using directed gassing of Al-Si alloys in a high pressure die casting foundry. As a control gas, rotary degasser with gaseous 20 % H2 in N2 as a medium was used. Castings were casted via high pressure die casting machine. The aim of this research is to compare internal defect such as porosity or shrinkage of a casts made from degassed and control gassed melt.