Les lacs d'altitude sont soumis à des retombées atmosphériques de polluants organiques persistants (POP) issus pour la plupart des activités humaines malgré leur éloignement des sources d'émissions de ces composés. Si les mécanismes de transport atmosphérique de ces polluants jusqu'aux sites d'altitude sont désormais bien connus (« global distillation » ou « grasshopper effect »), on dispose en revanche de très peu d'informations quant à leur devenir dans ces écosystèmes montagnards. Le travail présenté a pour objectif de déterminer les processus internes au lac influençant le devenir de ces polluants, avec un accent plus particulier sur leurs interactions avec les phases organiques et leur intégration dans les réseaux trophiques. En raison de leurs propriétés physico-chimiques très variables entre congénères (e.g., peu à très hydrophobes), les polychlorobiphényles (PCB) ont été choisi comme modèles de POP.L'étude a été conduite sur deux lacs alpins du Parc National des Ecrins (Isère, France): le lac de la Muzelle (2110 m) et le lac de Plan Vianney (2250 m). Le suivi en 2012 et 2013, à fréquence saisonnière,des concentrations en PCB des composants biologiques, des fractions particulaires et dissoutes et des flux atmosphériques déposés sur les lacs a permis d'évaluer à la fois les variations saisonnières, interannuelles, et entre les lacs, de la contamination de la faune piscicole et de les relier aux intrants atmosphériques et aux processus biogéochimiques lacustres.Nos résultats identifient la fonte du manteau neigeux comme vecteur rapide et important de transfert des PCB atmosphériques aux lacs d'altitude (40% des apports annuels en seulement 2 à 3 semaines). Le bilan de masse révèle aussi que les flux de PCB entrants sont supérieurs aux flux sortants des lacs et met ainsi en évidence leur rôle de puits de PCB atmosphériques. La distribution des PCB entre les phases "particules" et "eau" varie à la fois entre lacs et saisons, révélant une succession d'équilibre et de non-équilibre thermodynamiques. En effet, la couverture de glace en hiver isole les lacs de l'atmosphère et donc des sources de polluants, permettant aux PCB d'atteindre l'équilibre thermodynamique de partition entre les phases particulaire et dissoute. A l'opposé, en périodes d'eaux libres, les paramètres d'influence de l'adsorption des PCB sur la matière particulaire (température, concentration et nature des particules, concentration de PCB) répondent à la variabilité environnementale, empêchant l'atteinte de l'état d'équilibre. Enfin, si la contamination de la faune piscicole varie tant entre lacs qu'entre saisons, l'absence de relation entre concentrations en PCB et divers indicateurs trophiques (composition en isotopes stables du carbone ou biomarqueurs lipidiques) révèle que cette contamination ne dépend ni de l'habitat ni de la variabilité trophique des individus. Au contraire, la contamination de la faune piscicole est liée à la concentration des polluants en phase dissoute. Dans les lacs d'altitude, les POP, même s'ils sont présents à faible concentration, seraient donc essentiellement transférés à la faune piscicole par un phénomène de bioconcentration et non par un mécanisme de bioaccumulation.Nos résultats mettent en évidence la nécessité de mieux connaître l'éco-dynamique des POP, y compris dans les milieux faiblement contaminés. Dans un contexte de changement global pour lequel les intrants dans les écosystèmes d'altitude risquent de varier en intensité ou en temporalité, ces connaissances permettront (i) d'évaluer le rôle futur des lacs comme puits ou sources secondaires de POP pour l'atmosphère et (ii) prévoir l'évolution des niveaux de contamination de la faune piscicole dans les écosystèmes aquatiques éloignés des sources de production. / Altitude lakes undergo atmospheric deposition of persistent organic pollutants (POPs) resulting mainly from human activities despite their distance from emission sources. If the mechanisms driving the atmospheric transport of these pollutants to altitude environment are now fairly known ("global distillation" or "grasshopper effect"), there is still few information about their fate in these mountain ecosystems. This work aims to identify the internal lake processes influencing the fate of POPs, with a particular focus on their interaction with the organic phases and their integration into food webs. Due to their variability of physico-chemical properties between congeners (e.g., less to more hydrophobic), polychlorinated biphenyls (PCBs) have been chosen as POP models.The study was conducted on two alpine lakes from the National Park of Ecrins (Isère, France): Lake Muzelle (2110 m) and Lake Plan Vianney (2250 m). A monitoring was conducted in 2012 and 2013 to assess PCBs concentration in aquatic organisms, particulate and dissolved fractions and atmospheric PCBs inputs. Thus, seasonal, interannual and inter-lakes variability of PCBs level in fish have been assessed and linked to atmospheric inputs and biogeochemical lake processes.Our results show that snowmelt corresponds to an important and sudden flux of PCBs to altitude lakes (40% of annual contributions during the few weeks of spring thaw). Mass balance also reveals that PCBs inputs are higher than outputs, highlighting the role of altitude lakes as atmospheric PCBs sinks. PCBs partition between particulate and dissolved phases varies both between lakes and seasons, revealing a succession of thermodynamics equilibrium and non-equilibrium. In fact, when lakes are ice-covered, the water column is isolated from the atmosphere and therefore from sources of pollutants, allowing to reach a thermodynamic equilibrium partition of PCBs between the particulate and dissolved phases. On the contrary, when lakes are ice-free, parameters affecting PCBs adsorption on particulate matter (temperature, concentration and nature of the particles, PCBs concentration) are subject to environmental variability, preventing chemicals to reach thermodynamic equilibrium. Finally, even though PCBs fish contamination varies both between lakes and between seasons, the lack of relationship between PCBs concentrations and trophic indicators (stable isotope composition of carbon or lipid biomarkers) highlights that fish level of PCBs does not depend on habitat use and inter-individual trophic variability. In contrast, the PCBs concentration in fish is related to the concentration of pollutants in the dissolved phase. In altitude lakes, even though POPs are presented at low concentrations, these chemicals are mainly transferred to the fish compartment by bioconcentration rather than bioaccumulation.These results highlight the need to improve our knowledge on POPs ecodynamics even in low contaminated environments. In a context of global change for which pollutant inputs in altitude ecosystems might vary in intensity or temporality, this research appears essential to (i) assess the future role of altitude lakes as atmospheric POPs sinks or secondary sources and (ii) predict any modification of PCBs levels in fish in remote aquatic ecosystems.

Les bâtiments représentent un des principaux leviers d'action pour optimiser l'efficacité énergétique et la réduction des émissions de CO2 dans les villes. Afin d'optimiser les performances énergétiques, différentes études ont été menées sur les performances thermiques aussi bien du de point de vue de la conception, de la calibration de modèle que de l'impact de changement climatique. L'analyse de sensibilité vise à évaluer la part d'incertitude due à chacune des variables ou des paramètres qui peuvent influencer ces performances.La plupart des études en bâtiment menées dans la littérature se placent dans un cadre statique qui ne représente pas l'évolution du système. Il est très vite apparu nécessaire de développer des méthodes qui prennent en compte à la fois la dépendance des entrées et la dimension temporelle qui elle-même comporte toujours de la dépendance. Parmi les différentes méthodes d'analyse de sensibilité, nous avons privilégié la méthode globale, reposant sur le calcul des indices de sensibilité de Sobol. Le calcul effectif des indices de sensibilité permet de hiérarchiser les paramètres d'entrée en fonction de leur influence sur la sortieLes indices de Sobol peuvent se calculer de différentes façons. Nous nous sommes intéressés notamment à la méthode Pick and Freeze basée sur l'échantillonnage. Celle-ci repose sur l'hypothèse fondamentale et dans la pratique le plus souvent non vérifiée d'indépendance des entrées. Cela nous a amené du point de vue statistique à développer des techniques nouvelles pour tenir compte du caractère des entrées de type dynamique et dépendantes entre elles à la fois dans le temps et à chaque instant.Nous avons placé notre travail dans l'optique de méthodes permettant de se ramener au cas d'entrées indépendantes. Notre préoccupation a été de modéliser les entrées de manière souple, aisément transposable à d'autres situations concrètes et permettant des simulations relativement aisées. Afin de rendre compte du lien temporel entre les variables, nous avons choisi de considérer un indice dépendant de l'instant de calcul et de quantifier la variabilité de la sortie non pas seulement à la variabilité de l'entrée à l'instant t mais aussi à cette même variabilité provenant des instants précédents. Cette vision permet d'introduire la notion de mémoire utile pour le calcul de la sensibilité. Nous avons développé une méthode d'estimation des indices de Sobol pour des entrées dépendantes statiques a priori. Elle peut néanmoins être mise en œuvre pour des entrées dynamiques de courte mémoire mais les calculs sont alors très lourds dès que le nombre d'entrées est grand ou les mémoires importantes. Cette méthode permet de séparer des variables dépendantes de loi quelconque en des variables indépendantes de loi uniforme. Facile à mettre en œuvre ces méthodes d'estimation ne s'appuient pas sur des hypothèses d'indépendance des entrées, elles permettent alors un large éventail d'applications.Nous avons appliqué notre méthodologie à un bâtiment existant, apportant ainsi un outil utile à l'analyse du comportement thermique et donc à son optimisation. Nous avons pu montrer différentes situations en analysant l'ordre des variables suivant les sensibilités à partir de mesures. Deux critères ont été étudiés. Un critère de confort : l'étude de la température intérieure et un critère de performance : l'énergie de chauffage. / Buildings represent one of the main levers of action to optimize energy efficiency and reducing emissions of $ CO_2 $. To understand how perform energy consumption of a building, different studies have been conducted on the thermal performance both the point of view of design and model calibration as the climate change impact. Energy performance can be optimized according to these studies by evaluating the degree of uncertainty due to each of the variables or parameters that may influence performance. This stage is called sensitivity analysis.Most building studies in the literature are placed in a static framework that does not represent the evolution of the system. The variables whose sensitivity to be studied are either considered at a given time or the input-output models are not dynamic. It became necessary to develop methods that take into account both the dependence of the inputs and the temporal dimension which itself always involves dependence. Among the different methods of sensitivity analysis, we have focused on the global method, based on the calculation of Sobol sensitivity indices. Sobol index of a parameter (or group of parameters) is a statistical indicator of easy interpretation. It allows to measure the importance of this parameter (or group of parameters) on the variability of a scalar quantity of interest, depending on the model output. Sensitivity indices allow to rank input parameters according to their influence on the output.Sobol indices can be calculated in different ways. We focused on the Pick and Freeze method based on sampling. This is based on a fundamental assumption and in practice often unverified : inputs independence. This led us statistically to develop new techniques to take into account the dynamic characteristic of inputs and dependents both in time and in every moment. Our work focuses on methods that can bring back to the case of independent inputs. Our concern was modelled in a flexible way inputs, easily transferable to other concrete situations and allowing relatively easy simulations. The input-output relationships are not important as the only constraint, of course not trivial, possible simulation.In order to reproduce the temporal relationship between the variables, we chose to consider an index dependent, in the non-stationary case (especially if there are seasonal phenomena), on the time of calculation and quantify the variability of output not not only to the variability of the input at time $ t $, but also to the same variability from previous times. This vision allows to introduce the concept of usable memory for the calculation of the sensitivity.The second method that we have developed is an estimation method of Sobol indices for static dependent inputs a priori. It may nevertheless be implemented for dynamic inputs with short memory but the calculations are then very heavy when the number of inputs are large or own important memories. This method allows to separate dependent variables of any law in independent variables uniformly distributed.Easy to implement these estimation methods developed are not based on assumptions of independence of inputs. It then allows a wide range of applications.This method applied to an existing building can help improve energy management and can be useful in the design from the implementation scenarios. We could show different situations by analysing the variable order according to the sensitivities from measurements on a test building. Two criteria were studied. A criterion of comfort: the study of indoor temperature and performance criteria: the heating energy.

The two most common commercial copper baths are the acid sulfate copper bath and the alkaline cyanide copper bath. Alkaline copper baths are mostly used to coat parts with complex geometry and to avoid galvanic deposition when depositing a metal on a less noble substrate. Because of the toxicity of cyanide compounds, alternative baths have been developed using different complexing agents. The starting point of the present study is a cyanide-free strike bath developed for copper plating on Zamak substrates developed by the Institute for Technological Research of the State of São Paulo/ Brazil. The replacement of a raw material such as cyanide must be economically advantageous and technically feasible. Therefore, this study intended to propose an alternative to the treatment of liquid wastes from the mentioned bath, aiming at simultaneous water reclamation and chemicals recovery in a closed system. The electrodialysis membrane separation process was studied, using a laboratoryscale system operating with a synthetic solution simulating the rinsing waters from the HEDP-based bath. The feasibility of the technique was evaluated by analyzing operational parameters such as ion extraction, demineralization rate, concentration rate, current efficiency for each anionic specie and average energy consumption. Because HEDP is a chelating agent, the transport of Cu(II)-HEDP chelates through anion-exchange membranes was also evaluated by means of electrochemical methods. Chronopotentiometric and current-voltage curves were constructed for different model solutions containing the same compounds as the original bath. A relation between the presence of chelates in the solutions and the fixed ion exchange group could be established. Lastly, deposition tests were performed using electrolytes containing the recycled inputs and the characteristics of the coatings were analyzed. The results showed that an electrodialysis stack using strongly basic anion-exchange membranes was suitable to produce treated solutions and a concentrate containing the ions from the bath. The concentrate could be added to the copper bath to compensate eventual drag-out losses without affecting the quality of the coatings. Thus, the application of electrodialysis was shown to be a feasible alternative for recovering water and inputs from the evaluated solution, reducing the wastewater generation and saving natural resources. / Os dois banhos de cobre comerciais mais comuns são o banho ácido à base de sulfato e o banho alcalino à base de cianeto. Os banhos alcalinos são usados principalmente para recobrir peças com geometria complexa e para evitar a deposição por deslocamento galvânico quando se deposita um metal em um substrato menos nobre. Por causa da toxicidade dos compostos cianídricos, banhos alternativos vêm sendo desenvolvidos usando diferentes agentes complexantes. O ponto de partida do presente estudo é um banho toque isento de cianeto para deposição de cobre em substratos de Zamak, desenvolvido pelo Instituto de Pesquisas Tecnológicas / Brasil. A substituição de matérias-primas como o cianeto deve ser economicamente vantajosa e tecnicamente viável. Desta forma, este estudo pretendeu propor uma alternativa para o tratamento de resíduos líquidos do banho mencionado, visando à recuperação simultânea da água e das matérias-primas em um sistema fechado. Foi estudado o processo de separação por membranas de eletrodiálise, usando um sistema em escala laboratorial operando com uma solução sintética que simulava as águas de lavagem do banho à base de HEDP. A viabilidade da técnica foi avaliada por meio da análise de parâmetros operacionais, como a extração dos íons, a taxa de dessalinização, o percentual de concentração, a eficiência de corrente calculada para cada espécie iônica e o consumo médio de energia. Devido ao HEDP ser um agente quelante, o transporte de quelatos Cu(II)-HEDP através de membranas aniônicas foi avaliado por meio de métodos eletroquímicos. Curvas cronopotenciométricas e curvas corrente-potencial foram construídas para diferentes soluções sintéticas que continham os mesmos compostos que o banho original. A relação entre a presença de quelatos nas soluções e os grupos fixos de troca iônica pôde ser estabelecida. Por fim, testes de deposição foram realizados usando eletrólitos contendo os compostos reciclados e as características dos depósitos foram analisadas. Os resultados mostraram que o sistema de eletrodiálise usando membranas aniônicas contendo grupos de troca fortemente básicos pôde produzir soluções tratadas e um concentrado contendo os íons do banho. O concentrado pôde ser adicionado ao banho original para compensar eventuais perdas por arraste sem afetar a qualidade dos depósitos. Assim, a aplicação da eletrodiálise se mostrou uma alternativa viável para a recuperação de água e de insumos da solução avaliada, reduzindo a geração de efluentes e economizando recursos naturais.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / O fruto do morangueiro (Fragaria x anamassa Duch.) à apreciado no mundo inteiro, sendo o plantio realizado em diversas regiÃes, fato esse que ocorre pela existÃncia de cultivares adaptadas a diferentes climas. PorÃm na regiÃo Nordeste hà um grande desafio aos produtores e pesquisadores, devido principalmente Ãs temperaturas e evapotranspiraÃÃes elevadas e a baixa pluviosidade. Outro desafio à a busca por uma agricultura menos dependente de insumos minerais. Os biofertilizantes apresentam-se como uma importante ferramenta para a produÃÃo vegetal, sendo gerados a partir de produtos naturais obtidos da fermentaÃÃo de materiais orgÃnicos. Em consequÃncia, o objetivo deste trabalho foi de avaliar os efeitos de lÃminas de irrigaÃÃo e doses de biofertilizante bovino de fermentaÃÃo anaerÃbica, sob ambiente protegido do tipo telado, nas condiÃÃes climÃticas de Fortaleza, CearÃ. Para isso, o experimento foi conduzido na EstaÃÃo AgrometeorolÃgica da Universidade Federal do Cearà (UFC), em Fortaleza, no perÃodo de setembro a dezembro de 2012, sob ambiente protegido do tipo telado. O delineamento experimental foi em blocos casualizados em esquema de parcelas subdivididas, em que as lÃminas de irrigaÃÃo foram aplicadas via gotejamento (equivalentes a 33,3; 66,6; 100; 133,3; 166,6 % da evaporaÃÃo medida no tanque classe A, ECA), constituÃndo as parcelas. As quatro doses de biofertilizante bovino (125; 250; 375 e 500 ml semana- planta-Â) foram as subparcelas, com quatro repetiÃÃes. Foram avaliadas as trocas gasosas (fotossÃntese, condutÃncia estomÃtica, transpiraÃÃo e concentraÃÃo interna de CO2; aos 40 e 110 DAT), a biomassa (matÃria seca da raiz, da parte aÃrea e total), as variÃveis de colheita (diÃmetro, comprimento, nÃmero, massa mÃdia dos frutos e produtividade) e de pÃs-colheita (sÃlido solÃveis totais, pH, acidez titulÃvel e relaÃÃo sÃlido solÃveis/acidez titulÃvel). A dose de 375 mL semana- planta- apresenta-se como a melhor dosagem para a cultura do morangueiro no litoral cearense. As funÃÃes geradas para a maioria das variÃveis em funÃÃo das lÃminas de irrigaÃÃo foram polinomiais quadrÃticas, sendo as lÃminas Ãtimas prÃximas a 100% da ECA. A lÃmina de irrigaÃÃo equivalente a 126,92% da ECA e a dose de biofertilizante de 375 mL semana- planta- proporciona o maior desenvolvimento da biomassa. Recomenda-se para uma mÃxima produÃÃo, uma lÃmina de irrigaÃÃo equivalente a 101,35% da ECA e uma dose de biofertilizante de 375 mL semana- planta-Â. / The fruit of the strawberry (Fragaria x anamassa Duch.) Is enjoyed all over the world, with planting accomplished in several regions, a fact that occurs the existence of cultivars adapted to different climates. But in the Northeast there is a big challenge for producers and researchers, mainly due to high temperatures and evapotranspiration and low rainfall. Another challenge is the search for a less dependent on mineral inputs agriculture. Biofertilizers are presented as an important tool for crop production, being generated from natural product obtained from the fermentation of organic materials. In consequence, the aim of this study was to evaluate the effects of irrigation and levels of bovine biofertilizer anaerobic fermentation under protected environment of the screenhouse type, in the climatic conditions in Fortaleza, CearÃ. For this, the experiment was conducted in weather station at the Federal University of CearÃ, Fortaleza, from August to December 2012, protected under the greenhouse type environment. Experimental design was a randomized complete block in a split-plot design in that the irrigation was applied through drip (equivalent to 33.3, 66.6, 100, 133.3, 166.6% of class A evaporation measured in tank, ECA), constituted the main plots. The four levels of cattle biofertilizer (125, 250, 375 and 500 ml plant- week-Â) were the subplots with four replications. Were evaluated gas exchange (photosynthesis, stomatal conductance, transpiration, and internal CO2 concentration; at 40 and 110 DAT), the biomass (dry matter of the roots, shoot and total), the variables of harvest (diameter, length, number,average fruit weight and yield) and postharvest (total soluble solid, pH , titratable acidity and soluble solid ratio / acidity). The dose of 375 mL plant- week- is presented as the best dosage for strawberry culture in CearÃ. The functions generated for most variables depending on irrigation were quadratic polynomial, with the best irrigation depths near in the 100% of ECA. The irrigation depths equivalent to 126.92% of ECA and bovine biofertilizer dose of 375 mL plant- week-Â, provides further development of biomass. It is recommended for maximum production a irrigation depths equivalent to 101.35% of ECA and a bovine biofertilizer dose of 375 mL plant- week-Â.

Magister Philosophiae - MPhil / This study explored value-chain governance in the Tugela Ferry Irrigation Scheme in KwaZulu-Natal, and presents data on input markets, vegetable production and output markets. Rural poverty is a major problem in post-apartheid South Africa, and smallholder agriculture has been identified by the Economic Development Department as a key component of its New Growth Path framework. Some scholars argue that since water is a scarce resource, irrigation farming should form a key focus of pro-poor land redistribution policy. The 1994 democratic dispensation saw the dismantling of the agricultural homeland parastatals which managed these schemes, causing them to collapse or near collapse. Yet they may have the potential to reduce rural poverty. While markets are key for viable production of fresh produce, some scholars assert that globally, input suppliers, food processors and supermarkets dominate the agro-food industry resulting in negative outcomes for smallholder producers. In South Africa, four major supermarkets (which together claim 55% of retail market share) were in the past located mainly in cities, but the trend now is that they are moving to small towns and townships. There are documented cases where pro-poor governance of fresh produce value chains has resulted in positive outcomes in South Africa. The re-governing markets concept which postulates that a multi-stakeholder approach to making the governance of agricultural value chains pro-poor, is offered as a solution to reducing poverty. This thesis argues that the incorporation of smallholder farmers into modern markets remains ineffective in dealing with poverty because it includes only a few smallholder farmers and those included face exclusion when they are exposed to harsh market conditions.

Management-induced degradation of soil chemical and microbial quality is one of the most pressing concerns and a considerable threat to the sustainability of agroecosystems. However, information on this important issue is limited and largely based on short-term studies. A long-term experiment initiated in 1939 at the University of Pretoria provided a unique opportunity to assess the direct and residual effects of manure and inorganic fertilizers on soil chemical properties, microbial components and maize yield in rotation with field pea. Long-term addition of manure resulted in increased total organic C (TOC), total N and available P levels in the soil. Seasonally, these nutrients exhibited variations that appeared to be related to influences of crop rotation. Soil N content in an adjacent native site remained relatively constant but tended to increase in the control and manured plots. Soil microbial biomass C, N and P and microbial populations were affected by previous manure application as well as by crop rotation. Microbial biomass and numbers were generally higher in the manured plots. Manure application also had substantial residual effects and resulted in maize grain yields higher than in the control. Long-term NPK application resulted in decreased TOC and basic cation contents, and lowering of soil pH. The decrease in TOC was greater in single fertilizer treatments whereas basic cation contents and pH declined more in the balanced fertilizer treatments. Soil microbial biomass and numbers were influenced by, and exhibited qualitative changes in response to, long-term fertilization. Crop rotation also exerted effects on chemical and microbial properties of the soil. Maize grain yield showed significant increases in response to balanced fertilizer treatments. Response of maize to simple fertilizer applications was not beneficial in terms of yield returns. These results suggest that judicious use of inorganic fertilizers may, in the long-term, maintain soil quality and productive capacity. A comparison of the effects of residual manure and NPK fertilizers on the content of selected nutrients, microbial properties, C and N inputs, tissue nutrient concentration and crop yield showed differences due to treatments. TOC, total N and available P levels were increased due to residual manure alone or in combination with NPK fertilizers. C and N inputs and tissue P concentration were also generally higher in manured than in the NPK treatment. However, the higher increase in nutrient contents of manured plots was not reflected in microbial properties of the soil. Despite lower nutrient levels, the NPK treatment resulted in relatively greater increases in microbial properties of the soil. The differential responses were largely due to differences in quality and decomposability of organic material. Organic material in the NPK treatment appeared to have a higher decomposition and turnover rate than in other treatments, suggesting that C limitation in soils of low C but good nutrient supply may be compensated by high turnover rates of the available organic materials. The beneficial effect of residual manure on microbial properties and crop yield was decreased by application of supplemental N fertilizer but remained unaffected by application of supplemental K fertilizer. The depressive effect of excess soil P levels on soil microbial properties and crop yield was exacerbated by supplemental N fertilizer and mitigated by supplemental manure and K fertilizer applied to residual P. The decrease in available P levels due to supplemental K application implies that this may serve as a viable alternative to ameliorate soils with excess P levels. / Thesis (PhD (Plant Production and Soil Science))--University of Pretoria, 2003. / Plant Production and Soil Science / unrestricted

Le complexe des lobes terminaux du système turbiditique du Congo, localisé à 760 km des côtes de l’Afrique Equatoriale et à 5000 m de profondeur, constitue un système sédimentaire unique pour étudier les transferts de matière organique dans l’Océan Atlantique. En effet, ce complexe, d’une superficie de 3000 km² environ, est actuellement le réceptacle final des apports turbiditiques, initiés dans le canyon du fleuve Congo. Cette thèse, qui s’inscrit dans le cadre du projet ANR-Congolobe, a pour objectif d’apporter des connaissances sur la composition biogéochimique de ces apports et d’apporter des conclusions sur leur(s) origine(s), leur distribution et leur devenir dans les sédiments. Pour ce faire, neuf carottes d’interface (~20 cm) et une carotte longue (~900 cm) prélevées en différents sites du complexe des lobes ont été étudiées. La stratégie employée a consisté (1) à réaliser une description des faciès et de la granulométrie des sédiments, (2) à réaliser une étude géochimique globale et moléculaire sur ces mêmes sédiments (%Corg, C/N, δ13Corg et δ15N, 137Cs, acides gras, tétraéthers) (3) à confronter les données acquises avec celles obtenues sur les sources initiales marines et terrestres par un modèle de mélange binaire (δ13Corg) et par une analyse discriminante (acides gras), (4) à considérer un site spécifique en tant que référence temporelle, (5) à combiner les données acquises à tous les sites dans une analyse multivariée pour appréhender le devenir de cette région à l’échelle millénaire. Tous les marqueurs considérés ont révélé que les sédiments des lobes constituent un véritable puits de matière organique particulaire terrigène en provenance du Congo. Les concentrations en carbone organique sont élevées dans les sédiments argilo-silteux (~3 à 5 %). 70 à 80 % de ce carbone organique dérive du fleuve et consiste en des débris végétaux et en de la matière organique altérée issue de l’érosion des sols, alors que les 20 à 30 % restants consistent en une matière organique marine très dégradée. Une analyse plus détaillée des biomarqueurs lipidiques suggère que la matière organique apportée par les turbidites est peu réactive, néanmoins, l’analyse des acides gras a permis de détecter la présence de composés marins frais dans certains échantillons. Une conclusion importante de cette étude est que tous les résultats portant sur la composition et la distribution de la matière organique dans les sédiments sont en accord avec les modalités de dépôt turbiditique (rapidité du transfert, fréquence des apports, épaisseur des dépôts) ainsi qu’avec les propriétés granulométriques des sédiments. Ces caractéristiques physiques permettent d’expliquer que la matière organique soit exceptionnellement bien préservée dans les couches anoxiques des sédiments, une observation valable à l’échelle des millénaires qui soulève l’intérêt de prendre en compte la région des lobes pour comprendre le devenir de la matière organique terrestre dans l’océan global. / The terminal lobe complex of the Congo deep-sea fan, which is a unique region to study the transfer of organic matter from the land to the Atlantic Ocean, is located 760 km off the Equatorial African coast and at 5,000 m depth. This region covers 3000 km2 and is the terminal receptacle of the particulate organic matter provided by turbidity currents originating from the Congo River canyon. This thesis is part of the Congolobe ANR-project and aims at providing information on the biogeochemical composition of these organic matter inputs to study their origin, distribution and fate in lobe complex sediments. Nine short sediment cores (~20 cm) and one long core (~900 cm) were collected in different sites of the lobes complex for different sediment analyses. The strategy of the study consists of the following five analytical steps: (1) to achieve a facies and granulometry description of the sediments; (2) to study the global and molecular geochemical characteristics of the sediments (%OC , C/N, δ13Corg, δ15N, 137Cs, fatty acids and tetraethers); (3) to compare these data to data from marine and terrestrial end-members using a binary mixing model (δ13Corg) and a discriminant analysis (fatty acids); (4) to consider a specific site as a time reference and (5) to discuss the fate of the sedimentary organic matter at the millennium time scale of the overall area by combining different data in a multivariate analysis. All the different proxies used in this study revealed that lobe sediments could be a sink for organic inputs from the Congo River. Organic carbon concentrations are high in silty-clay sediments (~3 to 5 %). Over the study region, 70 to 80 % of the organic carbon originate from the Congo River and consist of vegetal detritus and soil derived-OM. The remaining 20 to 30 % consists of highly degraded organic matter. A more detailed lipid biomarker analysis shows that the organic matter is poorly reactive; however, fatty acid analyses reveal the presence of fresh planktonic compounds in some samples. An important finding of this study is that the composition and the distribution of the organic matter in sediments are consistent with turbiditic deposition patterns (e.g., rapidity of transfer, frequency and thickness of deposits) as well as with the granulometry properties of the sediments from the terminal lobe complex. Due to the specific sediment characteristics, organic matter is exceptionally well preserved in the anoxic sediment layers, reaching back to millennial time scales. Hence, studying the lobe complex area is of great interest for a better understanding of the fate of terrestrial organic matter in the global ocean.

This dissertation deals with the Corporate Social Responsibily and highlights the importace of evaluation of CSR activities. I have chosen T-Mobile Czech Republic a.s. as an example of a socially responsible company. I evaluate one of its CSR activities by LBG methodology. Based on the analysis contained in this dissertation TMCZ can be considered as a socially responsible company. Its CSR activities are not only beneficial for the community, but also for the company itself. The purpose of this disertation is to stimulate creation CSR annual report in TMCZ and point out the importace of close monitoring of supported projects, so that it would be possible to find out the efficiency of invested resources.

Management-induced degradation of soil chemical and microbial quality is one of the most pressing concerns and a considerable threat to the sustainability of agroecosystems. However, information on this important issue is limited and largely based on short-term studies. A long-term experiment initiated in 1939 at the University of Pretoria provided a unique opportunity to assess the direct and residual effects of manure and inorganic fertilizers on soil chemical properties, microbial components and maize yield in rotation with field pea. Long-term addition of manure resulted in increased total organic C (TO C), total Nand available P levels in the soil. Seasonally, these nutrients exhibited variations that appeared to be related to influences of crop rotation. Soil N content in an adjacent native site remained relatively constant but tended to increase in the control and manured plots. Soil microbial biomass C, Nand P and microbial populations were affected by previous manure application as well as by crop rotation. Microbial biomass and numbers were generally higher in the manured plots. Manure application also had substantial residual effects and resulted in maize grain yields higher than in the control. Long-term NPK application resulted in decreased TOC and basic cation contents, and lowering of soil pH. The decrease in TOC was greater in single fertilizer treatments whereas basic cation contents and pH declined more in the balanced fertilizer treatments. Soil microbial biomass and numbers were influenced by, and exhibited qualitative changes in response to, long-term fertilization. Crop rotation also exerted effects on chemical and microbial properties of the soil. Maize grain yield showed significant increases in response to balanced fertilizer treatments. Response of maize to simple fertilizer applications was not beneficial in terms of yield returns. These results suggest that judicious use of inorganic fertilizers may, in the long-term, maintain soil quality and productive capacity. A comparison of the effects of residual manure and NPK fertilizers on the content of selected nutrients, microbial properties, C and N inputs, tissue nutrient concentration and crop yield showed differences due to treatments. TOC, total N and available P levels were increased due to residual manure alone or in combination with NPK fertilizers. C and N inputs and tissue P concentration were also generally higher in manured than in the NPK treatment. However, the higher increase in nutrient contents of manured plots was not reflected in microbial properties of the soil. Despite lower nutrient levels, the NPK treatment resulted in relatively greater increases in microbial properties of the soil. The differential responses were largely due to differences in quality and decomposability of organic material. Organic material in the NPK treatment appeared to have a higher decomposition and turnover rate than in other treatments, suggesting that C limitation in soils of low C but good nutrient supply may be compensated by high turnover rates of the available organic materials. The beneficial effect of residual manure on microbial properties and crop yield was decreased by application of supplemental N fertilizer but remained unaffected by application of supplemental K fertilizer. The depressive effect of excess soil P levels on soil microbial properties and crop yield was exacerbated by supplemental N fertilizer and mitigated by supplemental manure and K fertilizer applied to residual P. The decrease in available P levels due to supplemental K application implies that this may serve as a viable alternative to ameliorate soils with excess P levels. / Thesis (PhD)--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

Road damage identification is still largely based on visual inspection methods and profilometer data. Visual inspection methods heavily rely on expert knowledge which is often very subjective. They also result in traffic flow interference due to the need for redirection of traffic to alternative routes during inspection. In addition to this, accurate high-speed profilometers, such as scanning vehicles, are extremely expensive often requiring strong economic justifications for their acquisition. The low-cost profilometers are very slow, typically operating at or less than walking speeds, causing their use to be labour-intensive if applied to large networks.This study aims at developing a road damage identification methodology for both paved and unpaved roads based on modelling the road-vehicle interaction system with an artificial neural network. The artificial neural network is created and trained with vehicle acceleration data as inputs and road profiles as targets. Then the trained neural network is consequently used for reconstruction of road profiles upon simulating it with vertical vehicle accelerations. The simulation process is very fast and can often be completed in a very short time thus making it possible to implement the methodology in real-time. Three case studies were used to demonstrate the feasibility of the methodology and the results on field tests carried out on mine vehicles with crudely measured road profiles showed a majority of the tested roads were reconstructed to within a fitting accuracy of less than 40% at a correlation level of greater than 55% which in this study was found to be practically acceptable considering the limitations imposed by the sizes of the haul trucks and their tyres as well as the quality of the road profiles and lack of control in the vehicle operation. / Thesis (PhD)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / Unrestricted