A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Okaukuejo 1993 / This study was designed to investigate the eco-physiology of baboons (Papio cynocephalus ursinus) in a troop living in the Kuiseb River canyon of the central Namib desert, Namibia. Answers were sought for two major questions: what Were the baboons prospects for survival and were there special adaptations allowing for their survival in their desert environment? To answer the former, life history phenomena of individuals and demographic changes within the troop were studied over a six year period. Results showed that the troop was not self-sustaining. Ectco-parasite infestations killed the majority of infants born to high ranking female baboons, while infant kidnapping by high ranking females killed most lower ranking females' infants. The high infant mortality appeared to affect the behaviour of adult male baboons in the troop, causing non-paternal males to fight harder to maintain a rank with reproductive opportunities, usually with serious wounding or death as a consequence. Answers to the latter question involved investigation into the baboons feeding patterns and diet, body temperature regulation, water flux rates and methods of body water conservation. Despite their desert environment, the baboons had access to plants of high water content and Were not dependent on free water intake. Plant foods also had low electrolyte concentrations. Body temparetures of three free-ranging baboons recorded by intraperitoneal radio tolemeters were remarkably labile, indicating an adaptive heterothermy. The baboons appeared to employ evaporative cooling only when water was available to drink and used cool sub-surface sand to slow their body temperature rises. water flux rates determined using tritiated water of three free-ranging baboons were not different to those of baboons from elsewhere. Acquisition of free water at times of water scarcity was strictly rank related. Body water conservation was apparently achieved through a combination of factors: urine concentration of Kuiseb baboons increased significantly when they were water deprived. The kidneys of the Kuiseb baboons, obtained from baboons that died naturally were anatomically significantly different and head greater urine concentrating abilities than the kidneys Of baboons from the northern Transvaal, South Africa. Kuiseb baboons showed efficient faecal water conservation, similar to other desert adapted mammals, Body water also was apparently conserved by engaging in water conservative behaviour, predominantly inactivity.

This paper proposes a deep study of the power consumption in Saudi Arabia homes. Today, clearly, Saudi homes waste a huge amount of power in each single home because of the high use rate for all home appliances. This is due, partially, to the extremely harsh desert climate in the country. There are many approaches to solve this problem; this paper will present one of the best solutions to solve the waste of the power in Saudi homes. The approach uses the latest technologies available today, including control tools and adopting the relying "Go Green" concept. The solution will be verified by verification and validation methods comparing the current home systems and the "Smart Hornes" system.

Drylands are characterised by patchy vegetation, erodible surfaces and erosive aeolian processes. The extreme nature of dryland environments means that semi-arid vegetation cover is often dynamic through time and space, due to complex relationships among plants, soil and transport processes. Understanding how ecogeomorphic processes interact and shape landscape evolution is critical for managing potential environmental and anthropogenic impacts in drylands, since these vulnerable regions are often used for pastoralism, agriculture and habitation. Despite a wealth of vegetation distribution models that simulate distinctive patterning that is often observed in drylands, relatively little is known about the effects of vegetation patch distribution, geometry and scale on the entrainment and transport of aeolian sediment. Empirical and modelling studies have shown that vegetation elements provide drag on the overlying airflow, thus affecting wind velocity profiles and altering erosive dynamics on desert surfaces. However, these dynamics are significantly complicated by turbulence, porosity and pliability effects in canopies. This thesis therefore presents new high-resolution field data for parameterising wind flow around individual plants and vegetation patches. Wind transport models have played a key role in simplifying aeolian processes in partly vegetated landscapes, but they remain challenging in some respects. Most models do not recognise the heterogeneous nature of desert surfaces, and those that do are often computationally expensive to run. Cellular automaton (CA) modelling has been successfully used to simulate dryland ecogeomorphic processes over large spatial and temporal scales. However, no existing CA model explicitly links vegetation growth, wind flow dynamics and sediment flux over a surface. This thesis presents a new CA approach that couples a sophisticated vegetation distribution model with a sediment transport model. The Vegetation and Sediment TrAnsport model (ViSTA) is verified and validated against existing dunefield theory and field datasets. ViSTA is then forced with potential 21^st century climate and land use change scenarios, to characterise possible transition scenarios between environmental states in the Kalahari Desert. ViSTA is shown to be a robust geomorphological tool for predicting landscape responses to a variety of human and environmental stresses.

For most of the animals, if not all, finding their way to a particular place is crucial for survival. To address this challenge of way-finding, different animals have evolved with different homing strategies. Social hymenopterans like honey bees, ants and wasps are of special interest – foragers of these insects show excellent homing capabilities while having simple neural resources. In this study field, honey bees and ants (desert ants, in particular) are among the most studied animals. Compared to these insects, our understanding on the homing mechanisms of social wasp is rather poor. For my thesis, I have studied homing behaviour of the tropical social wasp Ropalidia marginata, a predator in their foraging habit. To begin with, first I had to know their typical foraging range, which I found to be within about 500 m from their nest. Forager wasps possess a surprisingly well-developed familiarity with their foraging landscape, apparently more intricate than honey bees and desert ants. They acquire this spatial familiarity through flying around the landscape before starting foraging for food. Compared to honey bees and desert ants, this learning period in wasps appears to be much longer – this can be attributed to the much higher density of the tropical landscape in which they have evolved. I have also found that, if needed, they can fly to a distance of about 1.5 km for foraging and can return to their nest even if passively displaced to familiar and unfamiliar places. To return from unfamiliar places, they probably use some sort of searching mechanisms – a skill that they improve with their age. Such searching behaviour is prevalent throughout other hymenopteran insects. I conclude that capability and mechanisms of spatial orientation, navigation and homing in animals are much influenced by their evolutionary origin and the environment in which they have evolved.

Submitted by Noeme Timbo (noeme.timbo@metodista.br) on 2017-01-26T11:40:55Z No. of bitstreams: 1 Cecilia Toseli.pdf: 1189941 bytes, checksum: 0ab0914b4b6e1ae56436d73ef318ee0f (MD5) / Made available in DSpace on 2017-01-26T11:40:55Z (GMT). No. of bitstreams: 1 Cecilia Toseli.pdf: 1189941 bytes, checksum: 0ab0914b4b6e1ae56436d73ef318ee0f (MD5) Previous issue date: 2016-09-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This paper presents the Exodus-Desert tradition as Northern Israel foundational tradition, consolidated in the 8th century BCE, based on Bible reading 1 Kings 12.26 to 32. The passage 1 Kings 12.26-32 presents Jeroboam's religious measures to consolidate the independence of the newly founded Northern Kingdom, in relation to the "house of David" and the "house of Yahweh in Jerusalem" (v. 26-27). The passage perspective is clearly Judahite. However, we believe that, behind the 1 Kings 12.26-32 narrative, there are Exodus echoes as Northern Israel foundational tradition, consolidated during Jeroboam II reign (788-747). We have placed the historical core of the Exodus cultural memory in Northern Israel into the context of Sheshonq I military campaign (945-925) in Canaan, in the second half of the 10th century BCE. Although the "house of Saul" political-territorial defeat, located on the Gibeon-Bethel Plateau, the forced withdrawal of Egypt (for unknown reasons), in a short time, reignited the victory and freedom feeling in the remaining groups of the mountains, after centuries of Egyptian domination in Canaan. Therefore, the Exodus is born as a memory of fight against Egypt, and not as migration from Egypt. Thus, the Exodus God is conceived as a warrior divinity who leads his people, ensuring them victory. The Egypt withdrawal from Canaan lands shaped the path for Israel kingdom consolidation, under the Omrides govern, in the beginning of the 9th century BCE. Thus, it is possible to understand that the memory of freedom from Egypt has become an emblematic propaganda of the national state victory against his great enemy, after centuries of suffering and humiliation. On the other hand, the Exodus tradition remains as the resistance force against monarchical exploitation and oppression, as evidenced by Hosea and Amos' prophecy, in the 8th century BCE. The Desert tradition was an independent memory. It was attached to the Exodus tradition, probably during Jeroboam II reign (788-747), as evidenced by inscriptions and drawings located at Kuntillet 'Ajrud site. Based on Hosea and Amos' prophecy and according to Kuntillet 'Ajrud records, we consider that the national cult in Northern Israel, in the 8th century BCE, was dedicated to the Yahweh, represented as the "young bull" and associated with the Exodus, in shrines as Bethel, Dan, and Samaria. However, before Yahweh became Israel tutelary divinity, Egypt liberation memory had been assigned initially to the god El, an Ugarit pantheon supreme divinity, traditionally represented as a bull and associated with Asherah goddess. Another Northern Israel foundational narrative competes with the Exodus tradition during Jeroboam II reign, the Jacob tradition, associated with family memories. However, after Samaria fall, Jacob's old memories are once again read in Judah, submitted to Abraham tradition and supplanted by the Exodus tradition, which then becomes, from the end of the 7th century BCE, the foundational narrative of a unified Israel, considered one people from the beginning. / Esta pesquisa apresenta a tradição do Êxodo-Deserto como tradição fundante de Israel Norte, consolidada no séc. VIII a.EC, a partir da leitura de 1Rs 12,26-32. O texto de 1Rs 12,26-32 apresenta as medidas religiosas de Jeroboão para consolidar a independência do recém-fundado Reino do Norte, em relação à “casa de Davi” e à “casa de Javé em Jerusalém” (v. 26-27). A perspectiva da redação é nitidamente judaíta. Consideramos, porém, que, por trás da narrativa de 1Rs 12,26-32, encontram-se ecos do Êxodo como tradição fundante de Israel Norte, consolidada durante o reino de Jeroboão II (788-747). Situamos o núcleo histórico da memória cultural do Êxodo em Israel Norte no contexto da campanha militar de Sheshonq I (945-925) em Canaã, na segunda metade do séc. X a.EC. Apesar da derrota da entidade político-territorial da “casa de Saul”, situada no planalto de Gabaon-Betel, a retirada forçada do Egito (por motivos desconhecidos), em pouco tempo, reacendeu nos remanescentes grupos das montanhas o sentimento de vitória e de libertação, após séculos de dominação egípcia em Canaã. Neste contexto, o Êxodo nasce como memória de luta contra o Egito, e não de migração do Egito. O deus do Êxodo é, então, concebido como uma divindade guerreira, que vai à frente de seu povo, garantindo-lhe a vitória. A saída do Egito das terras de Canaã abriu caminho para a consolidação do reino de Israel, sob o governo dos Omridas, no início do séc. IX a.EC. Assim, é possível compreender que a memória da libertação do Egito tenha-se tornado propaganda emblemática da vitória do estado nacional contra o seu grande inimigo, após séculos de sofrimento e humilhação. Por outro lado, a tradição do Êxodo mantém-se como força de resistência contra a exploração e opressão monárquica, conforme atesta a profecia de Oseias e Amós, no séc. VIII a.EC. A tradição do Deserto constituía uma memória independente. Foi unida à tradição do Êxodo, provavelmente, durante o reinado de Jeroboão II (788-747), conforme atestam inscrições e desenhos do sítio de Kuntillet ‘Ajrud. A partir da profecia de Oseias e Amós e dos registros de Kuntillet ‘Ajrud, consideramos que o culto nacional em Israel Norte, no séc. VIII a.EC, era dedicado a Javé, representado na forma do “touro jovem” e associado ao Êxodo, em santuários como Betel, Dã e Samaria. Antes, porém, de Javé tornar-se a divindade tutelar de Israel, a memória da libertação do Egito teria sido atribuída, inicialmente, ao deus El, divindade-suprema do panteão de Ugarit, tradicionalmente representado na forma do touro e ligado à deusa Asherá. Concorre com a tradição do Êxodo, à época de Jeroboão II, outra narrativa de fundação de Israel Norte, a tradição de Jacó, ligada a memórias de família. Contudo, após a queda de Samaria, as antigas memórias de Jacó são relidas em Judá, submetidas à tradição de Abraão e suplantadas pela tradição do Êxodo, que se torna, então, a partir do final do séc. VII a.EC, a narrativa fundante de um Israel unificado, considerado um só povo desde as origens.

nÃo hà / O corpo poroso produz-se numa experimentaÃÃo que se faz na imanÃncia. Ele nÃo pode ser considerado propriamente um conceito, muito menos um objeto, mas um agenciamento em curso numa travessia singular. TraÃar as linhas e marcar os planos que o compÃem sÃo objetivos desta cartografia, que acompanha, ora movimentos de desterritorializaÃÃo, ora de reterritorializaÃÃo, deslizando e saltando entre estratos, percorrendo o interstÃcio da vida. Esses deslocamentos dÃo-se entre os planos da literatura, da saÃde, da filosofia e da educaÃÃo, seguindo linhas ora segmentares, molares, ora linhas flexÃveis, moleculares, impulsionando passagens, fluxos, escoamentos, fugas, vazamentos atravÃs do poro, conceito que permeia e fenestra todo o texto. A personagem clariceana G.H., uma mÃdica intensivista, T.K., e uma paliativista, E.L., atravessam e sÃo atravessadas por essas linhas, constituindo-se personagens conceituais e figuras estÃticas, que se movimentam no plano de imanÃncia, mas tambÃm em plano de composiÃÃo. A educaÃÃo à o plano sobre o qual conectam-se agenciamentos â cujos elementos envolvem instituiÃÃes de ensino superior, unidades de terapia intensiva, hospitais â em linhas segmentares â biomedicina, humanizaÃÃo em saÃde â e linhas molares â movimento estudantil, tamborete de bioÃtica, liga de saÃde da famÃlia, literatura. Nesse plano, a EducaÃÃo MÃdica estratifica-se em organismo e rosto (eixos de subjetivaÃÃo e de significaÃÃo) a que se articula um corpo sem ÃrgÃos (poroso) e movimentos de borramento do rosto para constituir cabeÃas, zonas de indiscernibilidade. As personagens, correndo todos os perigos, atravessam desertos, cruzam limiares de intensidade, margeiam linhas de mistÃrio e fogo e entram em devires numa tentativa de resistÃncia Ãs forÃas predominantes, de recusa à subjetividade capitalÃstica, de afirmaÃÃo de modos de vida outros, com implicaÃÃes Ãticas, polÃticas, estÃticas, epistÃmicas, tÃcnicas.

Dans le cadre de la politique de réduction des émissions de gaz toxiques tels que les composés organiques volatils (COV) et les oxydes d'azote (NOx), cette étude portait sur la mise au point de catalyseurs exempts de métaux nobles, efficaces pour l'élimination simultanée des COV (propène) et des NOx en présence d'un excès d'oxygène (milieu pauvre). Deux traitements ont été envisagés : d'une part nous avons étudié la réaction d'oxydation totale du propène et d'autre part les réactions simultanées d'oxydation du propène et de réduction des NOx. Le choix s'est reporté sur les matériaux hydrotalcites qui, après calcination, permettent d'obtenir un mélange d'oxydes ayant des propriétés intéressantes en catalyse. Dans un premier temps, des catalyseurs massiques à base de Cu, de Mg et de Al ont été synthétisés par voie hydrotalcite. Nous avons pu mettre en évidence que les espèces cuivriques sous formes de petits agrégats de CuO très dispersés à la surface sont actifs pour la réduction des NOx alors que les ions CU²⁺ sous forme de cristallites de CuO sont plus actifs dans l'oxydation du propène. Afin d'améliorer les performances catalytiques de ces catalyseurs, l'incorporation de l'élément Fe dans ces matériaux a été réalisée. Pour la réaction de réduction des NOx en présence de C₃H₆, la coexistence du fer et du cuivre dans un même matériau décale la fenêtre de température de conversion des NOx vers de plus basses températures mais également diminue la conversion de NO. Par ailleurs, en vue d'accroître les valeurs de conversion de NOx, le catalyseur qui convertit le mieux les NOx a été promu par des métaux alcalins. Cs et Na ont montré un effet promoteur tandis que K a exercé un effet inhibiteur dans la réaction de réduction des NOx. Dans la dernière partie de ce travail, une introduction à l'oxydation catalytique des suies et à l'élimination simultanée du propène et des NOx en présence de suies a été envisagée. Une autre partie du travail de thèse a concerné les particules atmosphériques qui ont été collectées au Liban durant une tempête désertique provenant du désert Arabe, le but étant d'évaluer le changement morphologique et chimique qui peut avoir lieu au cours du transport à longue distance. La caractérisation de ces particules par microcopie électronique à balayage couplée à un Spectromètre à Dispersion d'Energie a montré que les grosses particules sont riches en oxydes métalliques (notamment en Si, Al, Mg, Fe, Ca...). Sur les particules fines et ultrafines nous avons pu mettre en évidence la formation d'oligomères d'organonitrates et d'organosulfates. Or, ces organonitrates proviennent de la réaction entre les COV et les NOx. / This thesis was done within the politics of reducing the emissions of toxic gases such as volatile organic compounds (VOC) and nitrogen oxides (NOx). This study aimed to optimize efficient catalysts, prepared in the absence of noble metals, for the simultaneous elimination of VOC (propylene) and NOx under excess of oxygen (lean condition). Hydrotalcite solids were chosen because of the interesting properties of the oxides obtained by their calcination. Two treatments were performed : on the one hand the propylene oxidation alone, on the other propylene oxidation and NOx reduction simultaneously. Cu, Mg and Al - based catalysts were prepared by the hydrotalcite route. The as-prepared solids were proven to be efficient in the NOx reduction due to the presence of small aggregates of well dispersed CuO on the surface. However the CU²⁺ ions in the forms of crystallites were active in the propylene reaction. In order to improve the catalytic activity, Fe element was then incorporated into the solids to substitute a part or all of the Al element and the effects were studied. In the selective catalytic reduction of NOx by the C₃H₆ the introduction of iron species into the structure lowered the temperature of complete C₃H₆ conversion but also reduced the NOx conversion. Moreover, in order to improve the NOx conversion, the catalyst that exhibited the best reduction of NOx was promoted by alkaline letals. Cs and Na showed a promoting effect while K displayed an inhibotory effect. Finally, an introduction to soot oxidation and the simultaneous elimination of propylene and NOx in the presence of soot was conducted. Another part of this work concerned atmospheric particles collected in Lebanon during dust-rich days originating from the Arabian Desert. Transformations in the morphology and chemical composition of aerosols were assessed by Scanning Electron Microscopy (SEM) equipped with an Energy Dispersive X-ray system. The results showed that coarse particles are rich in metal oxides (Si, Al, Mg, Fe, Ca...). However, over fine and ultrafine particles, the formation of organonitrates and organosulfates oligomers was observed. Yet, organonitrates sprung from the reaction between VOC and NOx.

Les changements climatiques bouleversent toute la planète. Leurs impacts écologiques et socio-économiques sont une menace pour tous les pays, surtout ceux en voie de développement. Depuis 1990, la communauté internationale a pris conscience de ce phénomène et les pays développés sont pointés du doigt pour en être des responsables. Par conséquent, ils doivent fournir des efforts financiers et technologiques pour aider les pays les moins avancés à s’adapter. Aujourd’hui, les changements climatiques représentent un enjeu des relations internationales et sont abordés dans presque toutes les réunions internationales. Cependant, la gouvernance climatique mondiale peine à se mettre en place malgré les efforts accomplis par la communauté internationale. Les conférences sont le théâtre de rapports de force entre les États où prévalent les intérêts nationaux, souvent contradictoires. Les impacts des changements climatiques étant localisés, le Tchad apparaît comme un pays vulnérable, aux conséquences graves : avancée du désert, sécheresse, inondations, perte de biodiversité, appauvrissement des sols et diminution des ressources en eau, qui entrainent la baisse de la production agricole, l’insécurité alimentaire, les maladies, les conflits et les déplacements des populations. Bien que le Tchad soit mobilisé pour lutter contre les changements climatiques, il manque des capacités nécessaires pour relever ce défi. Cette thèse considère la zone sahélienne comme une des plus pertinentes pour l’analyse précise de ces impacts et pour la proposition de stratégies mieux adaptées pour lutter contre les changements climatiques. Il s’agit de mesures d’atténuation et d’adaptation qui consistent à mettre en œuvre des politiques nationales plus innovantes et plus ciblées, à créer de nouvelles infrastructures dans les secteurs des transports, des télé-communications, de l’énergie, et à impliquer l’ensemble des acteurs concernés. / Climate changes are upseting the whole planet. Their écologic and socio-economic impacts are a real threat for all countries, principally the developping ones. Since 1990, the international community has becoming aware of this and the developped countries are clearly showned as being mainly responsible. Consequently, they have to financially and technologically strive in order to help the less advanced countries to adapt. Nowadays, the climate changes represent a big stake in the inter-national relationships, they are debated in almost all international meetings. However, the world climatic governing is difficult to establish by the international community. The conferences are dominated by the frequent oppositions of the States’ national interests. As the impacts of climate changes are specifically localised, Chad appears as a vulnerable country suffering dramatic conse-quences: progression of desert, dryness, flood, loss of biodiversity, empoverishment of soils and diminishing water ressources which imply the decreasing ot the agricultural production, food unse-curity, deseases, conflicts and deportation of population. Although Chad is mobilised to struggle against climatic changes, it lacks the necessary capacity to confront this challenge. This thesis con-siders the sahelian zone as one of the most relevant to precisely analyse these impacts and for pro-posal of efficient strategies adapted to act against climate changes. It is about measures of mitiga-tion and adaptation which consist in operating more innovative and more targeted national politics, in creating new infrastructures in the sectors of transport, telecommunications, energy and in in-volving all the concerned actors.

La région sahariennne est une des zones les plus défavorables à la croissance et développement des espèces animales. Cependant, peu d’espèces possèdent à la fois des mécanismes morphologiques et écophysiologiques, assurant leur survie dans les sols arides et sur les dunes de sable.En effet, on peut estimer que le métabolisme secondaire biosynthétise des quantités considérables de composés bioactifs, destinés à assurer le développement et la continuité de ces espèces, notamment leur survie dans ces conditions sahariennes précaires.Les propriétés pharmacologiques des extraits de plantes sahariennes peuvent apporter des bénéfices dans la guérison de certaines maladies microbiennes ou prolifératives ou également contribuer au développement de certaines activités antioxydantes.L'étude des propriétés toxiques vise donc à enrichir la connaissance du potentiel bioactif des plantes sahariennes.Ces aspects de la puissance du métabolisme furent étudiés chez certaines espèces végétales strictement sahariennes. Il s’agit de : Anthyllis henoniana Coss., Centropodiaforskalii (Vahl) Cope, Cornulaca monacantha Delile, Ephedra alata var. alenda (Stapf.)Trabut, Euphorbia guyoniana Boiss & Reut., Henophyton deserti Coss. & Durieu,Hélianthemum confertum Dunal, Moltkiopsis ciliata (Forssk.) I.M.Johnst. et Spartidiumsaharae (Coss. & Durieu) Pomel. Les principaux résultats obtenus montrent que ces espèces possèdent des propriétés intéressantes, susceptibles d’être utiles pour le traitement de certaines maladies humaines.En revanche, parfois à certaines concentrations, des extraits de ces espèces peuvent présenter des effets toxiques sur les organismes.En dépit des conditions extrêmes, le Sahara représente la zone de développement d'une certaine diversité biologique, et principalement des espèces de plantes précieuses dont une meilleure connaissance scientifique de leur propriétés phytochimiques se révèle indispensable. / The Saharan desert is one of the most unfavorable areas, to the plant life. However, a small number of plants possesses both morphological and ecophysiological mechanisms ensuring their survival in the arid soil and on the sand dunes.It can be estimated that the secondary metabolism biosynthesizes considerable amounts of bioactive compounds, meant to ensure the development and the continuity of these species.The pharmacological properties of saharan plant extracts may bring benefits in the healing of certain microbial or proliferative diseases or contributes to the supply of antioxidants activities.The study of toxic properties is meant to enrich the knowledge of Saharan plants’bioactive potential.The biological activities of Anthyllis henoniana Coss., Centropodia forskalii (Vahl)Cope, Cornulaca monacantha Delile, Ephedra alata var. alenda (Stapf.) Trabut,Euphorbia guyoniana Boiss & Reut., Henophyton deserti Coss. & Durieu, Helianthemum confertum Dunal, Moltkiopsis ciliata (Forssk.) I.M.Johnst. and Spartidium saharae (Coss.& Durieu) Pomel have been studied. It can be seen that these species possess interesting properties, capitalized in the treatment of some human diseases. But, on the other hand in certain concentrations, extracts from these species may exhibit toxic effects onorganisms.Despite the extreme conditions, the Saharan desert represents the area of development for some valuable plant species, whose scientific knowledge is necessary.

Cette thèse de doctorat traite du comportement géochimique de Zr, Hf et Terres Rares dans des environnements aqueux extrêmes. Les études ont été effectuées dans les eaux hyper-salines long de la faille de la Mer Morte (Israël), les eaux hyper-acides dans le système volcanique hydrothermal du Nevado del Ruiz (Colombie) et les eaux riches en CO2 du système volcanique hydrothermal de l'île de Pantelleria, en comprenant le lac alcalin “Specchio di Venere”. Haute appauvrissement en Terres Rares légères a été trouvé dans les eaux acides dominées par le sulfate où on a reconnu la formation d’alunite et jarosite. Certaines eaux long de la faille de la Mer Morte montrent des enrichissements en Terres Rares intermédiaires, causés par la dissolution des minéraux évaporitiques. Les grandes variations redox et de pH observées dans ces systèmes hydrothermaux sont la cause des anomalies de Eu et Ce. Les eaux sulfates acides (1 < pH < 3.6) se caractérisent par des relations de Zr/Hf sous-condritiques et des relations condritiques de Y/Ho. Les rapports de Zr/Hf augment à l'augmentation du rapport Cl/SO4 en suggérant un comportement différent de Zr et Hf. Contrairement aux eaux acides, les relations de Y/Ho et Zr/Hf dans les eaux proches de la neutralité avec valeurs de Eh positives augmentent vers des valeurs super-condritiques, en raison de l'élimination préférentielle par les oxyhydroxydes de fer, de l'Hf et Ho que de Zr et Y. Le distribution des Terres Rares, avec les rapports de Y/Ho et Zr/Hf du “Specchio di Venere” montrent l’interaction entre les particules atmosphériques qui viennent du désert du Sahara et le lac “Specchio di Venere”, démontrent qu’ils sont de traceurs géochimiques. / This thesis concerns the geochemistry of Zr, Hf and REE (Rare Earth Elements) in extreme water environments. The investigations were carried out in hypersaline waters covering a wide range of Eh values along Dead Sea Fault (Israel), in hyperacid waters circulating in Nevado del Ruiz volcano-hydrothermal system (Colombia) and in CO2-rich waters in Pantelleria volcano-hydrothermal system (Italy), including the alkaline lake “Specchio di Venere” within a calderic depression. The acidic sulphates waters characterized by the precipitation of alunite and jarosite show a strong LREE depletion. The REE in waters along Dead Sea Fault show MREE enrichments in waters with relative high Ca and SO4 concentrations due to the water interaction with MREE-enriched salt minerals. In the natural waters, changing of pH and Eh induce variations of Ce and Eu anomalies, due to the different behaviour of these elements with respect to the neighbours REE. In sulphate acidic waters, Zr/Hf ratios are very low down to 4.7, while quite constant Y/Ho ratio (close to the local rock value) indicates the lack of decoupling. Zr/Hf ratio increases as Cl/SO4 ratio increases. On the contrary, Zr/Hf and Y/Ho ratios in near-neutral pH waters with positive Eh values change from near-chondritic to super-chondritic. The precipitation of Fe-oxyhydroxides removes preferentially Hf and Ho with respect to Zr and Y. The interaction of atmospheric fallout from the nearby Sahara Desert with the water of the lake “Specchio di Venere” was recognized by the Zr, Hf and REE distribution. Zr, Hf and REE show the capability to trace the interaction process between open water bodies and atmospheric fallout.