Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-20T12:14:48Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Gerlânia_Brasiliana_de_Arruda.pdf: 2687111 bytes, checksum: 4b8b65eb3d4dc07813155ca57fbaecda (MD5) / Made available in DSpace on 2016-09-20T12:14:48Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Gerlânia_Brasiliana_de_Arruda.pdf: 2687111 bytes, checksum: 4b8b65eb3d4dc07813155ca57fbaecda (MD5) Previous issue date: 2016-04-20 / Propriedades físico-químicas de águas superficiais represadas (profundidade: 30 cm) da região de Araripina, envolvendo pH, condutividade, OD, STD, temperatura, sulfatos, cloretos e bicarbonatos, são apresentadas neste trabalho. Este estudo foi motivado por pesquisas médicas que indicaram a poeira de gesso como responsável por 38% das internações hospitalares locais. A amostragem, no final da estação chuvosa, pressupõe um máximo de lixiviação da poeira de gesso sedimentada em solos e vegetação. A partir de focos produtores, os resultados permitiram configurar halos hidroquímicos de contaminação originados pela lixiviação da poeira de gesso e por efluentes da produção de placas de gesso. Posteriormente esses dados foram comparados com amostragem com período de estiagem. Estes halos envolvem centenas de metros de extensão, com período de estiagem orientado predominante dos ventos, determinando áreas de influência onde águas represadas e de subsuperfície estão contaminadas em SO4— (>250 mg/L até 1930 mg/L) e em cloretos (>250 mg/L até 5390 mg/L). Esta associação hidroquímica é atribuída à lixiviação de particulados de gesso e à provável presença de halita residual neste produto. A drenagem a jusante de Araripina revela contaminações por efluentes da produção de placas de gesso no domínio urbano, com contribuição adicional de efluentes domésticos sódicos e/ou clorados. No interior dos halos de dispersão de poeira/efluentes de gesso, águas represadas com concentrações elevadas em cloretos (> 200 mg/L) e sulfatos (> 250 mg/L), estão inviáveis para consumo humano. Elevadas taxas de dissolução e de residência de sulfatos e cloretos, nestes meios líquidos, mostraram aumento de concentração sulfatos e cloretos nos corpos d'água estudados principalmente no quadro de estiagem prolongada. / Physicochemical properties of dammed surface water (depth: 30 cm) of Araripina region, involving pH, conductivity, DO, TDS, temperature, sulfates, chlorides and bicarbonates, are presented in this paper. This study was motivated by medical research that indicated the dust plaster responsible for 38% of local hospitalizations. Sampling at the end of the rainy season, it assumes a maximum of dust leaching gypsum sediment in soils and vegetation. From producers outbreaks, the results helped set hydro chemical halos of contamination arising from the leaching of plaster dust and waste from the production of plasterboard. Subsequently these data were compared with a sample with the dry season. These halos involve hundreds of meters long, with prevailing dry season winds oriented, determining areas of influence where backwaters and subsurface are contaminated in SO4- (> 250 mg / L to 1930 mg / L) and chlorides (> 250 mg / L to 5390 mg / L). Hydrochemistry This association is attributed to leaching of gypsum particles and the probable presence of residual halite this product. Draining the Araripina downstream reveals contamination by waste from the production of plasterboard in the urban area, with additional contribution of sodium and / or chlorinated domestic sewage. Inside the dispersion halos of dust / waste gypsum, water dammed chlorides in high concentrations (> 200 mg / l) and sulphate (> 250 mg / L), are unfeasible for human consumption. High dissolution rates and residence of sulphates and chlorides, these liquid media showed increased concentration sulfates and chlorides in water bodies studied mainly in prolonged drought frame.

The headwaters of the Bear River in the Uinta Mountains of Utah provide a good setting in which to examine the influence of geological materials on stream chemistry. Ionic contributions to the stream-water from soils, vegetation, and the atmosphere generally are sparse enough that they do not mask the geologic contributions. Samples from 37 sites on the four major headwater streams and several minor tributaries were examined geochemically. Data derived from the samples allowed the construction of a hydrogeochemical weathering model specific to the study area. A significant feature of this model is that carbonic acid is the dominant chemical agent involved in geochemical weathering. The aim of this study was to examine the geologic influences on river chemistry. However, atmospheric contributions dominate the hydrochemistry through at least the first 10 kilometers of stream length for the easternmost three of the four major headwater streams. Except for the atmospheric contribution, surface-water chemistry is dominated by the groundwater chemistry, which is indelibly marked by the lithology the groundwater passes through. Other geologic factors in the study area that appear to influence groundwater chemistry, and hence stream chemistry, are the glacial till and outwash deposits and a major zone of east-west trending high-angle thrust faults. A technique for estimating the hydrochemistry of the groundwater based on surface-water chemistry and flow measurements was developed in this study.

Stimulating in situ microbial communities in oil reservoirs to produce natural gas is a potentially viable strategy for recovering additional fossil fuel resources following traditional recovery operations. Little is known about what geochemical parameters drive microbial population dynamics in biodegraded, methanogenic oil reservoirs. We investigated if microbial community structure was significantly impacted by the extent of crude oil biodegradation, extent of biogenic methane production, and formation water chemistry. Twenty-two oil production wells from north central Louisiana, USA, were sampled for analysis of microbial community structure and fluid geochemistry. Archaea were the dominant microbial community in the majority of the wells sampled. Methanogens, including hydrogenotrophic and methylotrophic organisms, were numerically dominant in every well, accounting for, on average, over 98% of the total Archaea present. The dominant Bacteria groups were Pseudomonas, Acinetobacter, Enterobacteriaceae, and Clostridiales, which have also been identified in other microbially-altered oil reservoirs. Comparing microbial community structure to fluid (gas, water, and oil) geochemistry revealed that the relative extent of biodegradation, salinity, and spatial location were the major drivers of microbial diversity. Archaeal relative abundance was independent of the extent of methanogenesis, but closely correlated to the extent of crude oil biodegradation; therefore, microbial community structure is likely not a good sole predictor of methanogenic activity, but may predict the extent of crude oil biodegradation. However, when the shallow, highly biodegraded, low salinity wells were excluded from the statistical analysis, no environmental parameters could explain the differences in microbial community structure. This suggests that the microbial community structure of the 5 shallow, up-dip wells was different than the 17 deeper, down-dip wells. Also, the 17 down-dip wells had statistically similar microbial communities despite significant changes in environmental parameters between oil fields. Together, this implies that no single microbial population is a reliable indicator of a reservoir's ability to degrade crude oil to methane, and that geochemistry may be a more important indicator for selecting a reservoir suitable for microbial enhancement of natural gas generation.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-08-16T15:50:35Z No. of bitstreams: 1 DISSERTAÇÃO - FINAL.pdf: 7338222 bytes, checksum: 196e18ecc90db3ce259dd90644d24860 (MD5) / Made available in DSpace on 2017-08-16T15:50:35Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO - FINAL.pdf: 7338222 bytes, checksum: 196e18ecc90db3ce259dd90644d24860 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A presente pesquisa hidrogeoquímica teve como intuito caracterizar o comportamento físico-químico, a composição mineralógica, a quantificação e composição química dos sedimentos e da água da microbacia do Córrego do Bule. Região essa, alvo de exploração mineral de sulfeto de antimônio nas décadas de 1920 e 1930, na qual hoje se encontra complemente soterrada. A microbacia está localizada na porção centro-sul do Sinclinal Dom Bosco, sul do Quadrilátero Ferrífero. Foram utilizadas diversas técnicas analíticas, juntamente com informações fisiográficas, geológicas e interpretações dos resultados estatísticos, que permitiram a determinação dos agentes controladores e carreadores, o desenvolvimento de backgrounds e a identificação de anomalias. Além disso, foi realizada a medição da vazão, a análise dos parâmetros de qualidade de água, quantificação da composição iônica e os metais dissolvidos na água. A composição mineralógica foi caracterizada a partir das análises de DRX sobre os sedimentos, onde se obteve a identificação da presença predominante de óxidos de ferro, como a goetita, hematita, bem como, caulinita e quartzo. Em sua composição química, destacam-se as altas concentrações de ferro justificada pela litologia local e o empobrecimento em alumínio, o qual reflete um alto grau de maturidade e/ou avançados processos de intemperismo químico. Há também a presença dos elementos traços como As, Cu, Pb, Sb e Zn, sendo estes associados a presença de mineralizações auríferas mesotermais hospedadas em greenstone belts e os elementos As, Co, Cr, Mn, Ni e Sb na composição de lateritas. A influência antrópica na área de estudo é praticamente nula. Isso se deve à microbacia estar contida em uma área de proteção ambiental permanente e longe de grandes centros urbanos e áreas de agropecuária. Portanto, é possível afirmar que as concentrações de metais são provenientes de fontes naturais / This hydrogeochemical research aimed to characterize the physicochemical behavior, mineralogical composition, quantification and chemical composition of sediments and water in the watershed of the Corrego do Bule. This area, which today is completely buried, was mined for antimony sulfide in the decades of 1920s and 1930s. The watershed is in the center-south of the Syncline Dom Bosco, south from the Iron Quadrangle. Several analytical techniques were used together with physiographic geological and statistical data interpretation. This allowed us to determine the controlling agents and carriers, the development of backgrounds and the identification of anomalies. In addition, we measured the flow pressure, analyzed the water quality parameters, quantified the ionic composition and dissolved metals in the water. The mineralogical composition was characterized by the XRD analyzes on the sediments where it was possible to identify the predominant presence of iron oxides, such as goethite, hematite, as well as, kaolinite and quartz. On its chemical composition, the high concentrations of iron are justified by the local lithology and the impoverishment in aluminum which reflects a high degree of maturity and / or advanced processes of chemical weathering. There are also the presence of some elements traces such as As, Cu, Pb, Sb and Zn, which are associated with the presence of mesothermal aureation minerals in greenstone belts and the elements As, Co, Cr, Mn, Ni and Sb in laterites. The antropic influence in the study area is practically null. This is because the watershed is contained in an area of permanent environmental protection and away from large urban centers and agricultural areas. In this way, it is possible to state that the concentrations of metals come from natural sources

Masters of Science / This study was conducted to investigate hydrogeochemical processes controlling the evolution of groundwater chemistry and their influence on water quality in the Heuningnes Catchment. The role or influence of hydrogeochemical processes in groundwater quality in aquifer systems remains poorly understood. One of the ways of improving such understanding is to employ different techniques to explore key processes that govern groundwater quality in aquifer systems. Therefore, the present study investigated hydrogeochemical processes of groundwater resources and identified key processes that explained its quality from a spatiotemporal perspective. The quantitative approach that provides the ability to assess relationships between variables both spatially and temporally was applied. Groundwater sampling was done on four occasions during July 2017, October 2017, March 2018, and July 2018. Identification of hydrogeochemical processes controlling the evolution of groundwater chemistry and quality was done using various complementary tools. These tools included classification of the main water types, evaluation of water-rock interaction by means of stoichiometry analysis and bivariate correlation plots, inverse geochemical modelling, and statistical analysis (hierarchical cluster analysis and factor analysis). Physical parameters were measured in situ, while water samples were collected from boreholes, piezometers, springs, and artesian boreholes for laboratory analysis for major ions analysis. Descriptive and bivariate statistical methods were used to summarise and evaluate the strength of the relationship between variables, while multivariate statistical methods were applied to group similar samples based on their chemical compositions. Tri linear Piper diagrams were generated to characterize water type based on double normalizing the proportions of cations and anions, while correlation and stoichiometric analysis were applied to identify hydrogeochemical processes influencing groundwater chemistry. The results generated from the trilinear Piper diagrams confirmed the dominance of sodium and chloride ions in waters of the Heuningnes Catchment. Groundwater of a Na/Cl type is typical for a coastal aquifer characterised by saline, deep ancient groundwater. The lower parts of the Catchment were characterised by saline groundwater. The results indicated that shallow groundwater samples within the study area were more mineralised as compared to deep groundwater with EC values ranging between 20.8 and 2990 mS/m, with waters within the Table Mountain Group region (TMG), recording the lowest values. Deep groundwater for boreholes and artesian boreholes located upstream in the Catchment was fresh and yielded some of the lowest EC values recorded with an EC value below 50 mS/m. Generally, EC values increased from the upper TMG region of the Catchment towards the Bokkeveld shale region downstream and were highest during the dry season of 2018. The results indicated strong geological influences on water chemistry. Bivariate correlation and stoichiometric analysis identified cation exchange, adsorption, evaporation, weathering of carbonates, sulphates and silicate minerals as processes influencing the chemistry of groundwater in the Heuningnes Catchment. The Saturation Index (SI) results showed a change of calcite, dolomite, aragonite, gypsum, anhydrite, halite, melantinterite, siderite and sylvite from being undersaturated to oversaturated at some areas for the different seasons along the flow path. The mass-balance modelling results indicated that ion exchange and reverse ion exchange processes were more dominant at low elevations along the same flow path during the dry periods. However, at high elevations along the flow path, silicate weathering was the dominant process taking place. The findings of this study demonstrated the influence of hydrogeochemical processes in changing the water chemistry along the flow paths. In conclusion, the study showed the value of utilising various assessment tools as complementary techniques to improve the understanding about hydrogeochemical processes, and its influence on evolution of groundwater chemistry and quality. Based on the findings of the study the following recommendations were made for future studies; the sample points or sample boreholes in the study Catchment should be increased; and to have more sampling trips to enable better comparison between the possible processes

No description available.

Groundwater chemistry is a function of recharge and the input chemistry of the rain, which gets transformed as it moves through the soil matrix. Apart from mineral transformations, anthropogenic activities are other external factors, which affect the groundwater chemistry. Stream – aquifer interactions alter the chemistry of groundwater in the regions nearer to the stream. A study is carried out to analyse the hydrogeochemical behavior under the influence of lithologic, precipitation and anthropogenic controls in the upper Cauvery basin. This is followed by the analysis of contributions made by the components of the hydrogeochemical cycle. A geochemical model is developed, which is used to study the spatiotemporal variations in groundwater chemistry of a silicatic rock group in a small experimental watershed. In order to study the effects of precipitation control on the groundwater chemistry the Upper Cauvery river basin (~ 10000 km2) is selected for the analysis, which stretches along three climatic zones – ‘semi-arid’ (500 – 800 mm/year rainfall), ‘sub-humid’ (1000 - 1200 mm/year) and ‘humid’ (1200 – 1500 mm/year) zones. The basin is mainly formed by granitic gneissic group of rocks with some traces of amphibolites and charnockites. Groundwater is observed to occur either in the saprolite or in the deeper hard rock zone based on the geomorphology even at the scale of a small watershed. Parts of this basin are under canal irrigation and are drained by Kabini and Cauvery Rivers. Groundwater – surface water interactions play an important role in these regions. Irrigation with different levels of intensities is practiced through groundwater in the upland areas. Observation wells considered in these three zones are classified into four classes based on the mean annual groundwater fluctuations. Wells in each of these four classes are further classified into ‘shallow’ and ‘deep’ categories based on the depth to groundwater. Analysis of the groundwater chemistry in the basin (widely spread with 120 wells in the three zones) shows a gradient in chemistry along the climatic gradient with sub-humid zone bridging between the semi-arid and humid zones. Ca/Na and Mg/Na ratios decrease from humid zone (unimodal rainfall) to semi-arid (bimodal rainfall) zone since both Na and Mg concentrations in groundwater increase along this gradient. These elements are mainly controlled by weathering reactions. Apart from the weathering of Ca, calcrete formations also play an important role in the semi-arid zone. Ion exchange process cycles between Cl and SO4 and between Ca and Na. Dissolution of CaCO3, silicate weathering and evaporation are the major mineralogical reactions. Variations in Na/Cl and Ca/Cl molar ratios indicate that shallow wells have higher molar ratios with higher variance than the deeper wells. Semi-arid zone is more silicaceous (higher Na/Cl value) than the humid zone, which has higher Ca/Cl ratio (~ 14). Effective seasonal patterns are identified using ‘recharge – discharge’ concept based on the rainfall intensity. Wells under normal scenario have low Na/Cl and Ca/Cl ratios in the ‘recharge period’ than in the corresponding ‘discharge period’ (dilution chemistry). Wells in the relatively higher pumping regions, which receive sufficient annual recharge exhibit dilution chemistry though groundwater level fluctuations are higher. However, wells in regions with insufficient recharge show ‘anti - dilution’ chemistry. Thus, the ‘recharge – discharge’ concept is useful in identifying the pumped wells from deeper wells and helps in characterizing the anthropogenic effects on the basin. Rainfall and its chemistry are to be analysed to understand the groundwater chemistry. Hence, data from various monitoring stations in India are analyzed for assessing the influence of several major factors such as, topographic location of the area, its distance from sea and annual rainfall. These stations are categorized as ‘urban’, ‘suburban’ and ‘rural’. pH, HCO3, NO3 and Mg concentrations have not changed much from coast to inland. On the other hand, SO4 and Ca concentrations changes are subjected to local emissions. Cl and Na (marine elements) originate solely from sea and a model is developed to quantify the variation in concentration of these elements under the influence of inland distance and annual rainfall. Non – linear regression model for the various categories shows that both rainfall amount and precipitation chemistry follow a power law reduction with distance from sea. Cl and Na decrease rapidly for the first 100 km distance from sea, then decrease marginally for the next 100 km and then later stabilize. Regression parameters estimated for different cases are found to be consistent (R2 ~ 0.8). Variation in one of the regression parameters accounts for the effect of urbanization. Model developed for precipitation chemistry is validated using stations from the southern peninsular region of the country. Model predictions are found to be in good correlation with observations with a relative error of ~ 5%. This relationship between the three parameters – rainfall amount, coastline distance, and concentration (in terms of Cl and Na) was validated with experiments conducted at Mule Hole SEW and Kalekere. Monthly variations in precipitation chemistry at these stations are predicted from a downscaled (in time) model and then compared with the observed data. Models developed at both annual and monthly scale are found to perform well with the field observations. Hence, this model is used for predicting the precipitation chemistry (in terms of Cl and Na) of different station points in the upper Cauvery basin. Comparative performance of alternate methods of recharge estimation i.e. Chloride mass balance (CMB) and water table fluctuation (WTF) approaches, is analyzed at various stations in the basin. Annual rainfall, Cl concentration in rain (predicted from precipitation model) and the concentration of Cl in the groundwater are the inputs for the CMB approach. Since main source of Na is from atmosphere, Na is taken as an alternative for Cl in the CMB approach and recharge is estimated using sodium mass balance (SMB) approach. Na concentrations contributed from weathering are quantified and eliminated in the analysis. Recharge estimated using SMB approach is found to be higher than CMB estimate in the semi-arid and the sub-humid zones. Water table fluctuation (WTF) method is used to compare the recharge obtained from both CMB and SMB approaches. Estimates using WTF approach are found to be higher than both CMB and SMB in the semi-arid and the sub-humid zones while SMB is found to be higher than CMB estimates. SMB and WTF estimates match well in the humid zone. An exponential relationship between recharge and annual rainfall is observed. Recharge coefficient estimated on an annual scale varied from 0.1 to 0.25 across the basin. Among CMB and SMB approaches, SMB is a better alternative for recharge estimation in semi-arid zones, where WTF approach performed poorly. Water – rock reactions are driven by the inequilibrium reactions of water with the mineral assemblage in the rock. These reactions evolve towards equilibrium with the primary minerals while a series of secondary minerals precipitate. Mass balance approach is adopted to quantify the rate at which the water – rock interactions occur in order to reach the equilibrium. Field experiments in the experimental watershed (Mule Hole SEW, ~ 4.5 km2) are carried to identify the minerals present in the region and their composition. Quartz, oligoclase, sericite, epidote and chlorite are the primary minerals while kaolinite and Fe-oxides are the secondary minerals present in this region. Percentages of oxides of different elements in each of these minerals are determined from the field experiments. Stoichiometric coefficients of different elements in each of these minerals are determined from these percentages. Long – term weathering rates are determined using these stoichiometric coefficients along with the mass fluxes of each element. Set of minerals present at different depths are found to vary among the thirteen observation wells of Mule Hole SEW. Hence, the mass balance calculations resulted in different weathering rates for a particular mineral based on the spatial location and the particular depth of the occurrence of the mineral. These weathering rates are tested for the sensitivity to carbonates with the inclusion of calcite in the mass balance calculations. With this sensitivity analysis it is observed that the presence of carbonates in the nodular form in the shallow wells has not changed the weathering reactions and their rates, and hence these wells are termed to be in the ‘silicate with secondary carbonate’ system. On the other hand, carbonates are not present in deeper wells, inclusion of which alters the equilibrium of the mass balance calculations. Thus, these wells are said to belong to the ‘silicate’ system. Anorthite present in some of the wells (MH2 and MH6) dissolves accompanied with the dissolution of carbonates. These wells are observed to belong to the third group the ‘amphibolites with primary carbonate’ system. Weathering rates of all the minerals present in these three different systems are also determined annually (short term rates). Mean of these short – term rates are observed to be the same as the long – term (over a period of 4 years) weathering rates with a minor difference of 3 – 10% in values. Thus, the weathering rates determined using mass balance approach is used to determine the quantities of concentrations of different elements contributed from the mineralogical reactions. Temporal variations in the concentrations of different chemical species in this small experimental watershed are simulated using a hydrogeochemical model. The model is developed based on a mixing cell approach, which considers the spatiotemporal variations in the recharge and the weathering inputs. Most of the weathering reactions are observed to take place in the saturated zone, which is termed as the ‘mixing zone’. This zone extends from few meters above the groundwater table to few meters below the water table. Mixing zone is discretized into series of ‘cells’ and concentrations in this zone are simulated. This group of cells is assumed to move along with the groundwater fluctuation. Sensitivity of the model is analysed subject to the variations in the recharge and the weathering fluxes. The developed model is used to simulate the concentrations of the groundwater in the three systems – ‘silicate’, ‘silicate with secondary carbonate’ and ‘amphibolites with primary carbonate’. Field data for chemical species is observed to vary in this mixing zone, boundaries of which are defined from the model simulations. Simulations corresponding to the cell at the mid depth of this mixing zone are observed to correlate well with the field data. Hence, the model developed is able to simulate the temporal variations in the groundwater chemistry. In summary, the study analyses the effects of lithological, climatic and anthropogenic factors on groundwater chemistry. The transformations in the rainwater chemistry as it reaches groundwater are analysed along different stages. A hydrogeochemical model is developed to simulate the groundwater concentrations in three different mineralogical settings over a period of three years.

L’objectif de cette thèse est d’arriver à mieux contraindre les paramètres qui contrôlent les processus d’altération à l’échelle d’un petit bassin versant, en se focalisant plus précisément sur le rôle de l’hydrologie. Pour ce faire, les variations temporelles et spatiales des signatures chimiques et isotopiques (U, Sr) des eaux du bassin versant du Ringelbach (Vosges, France) sont étudiées. Plusieurs sources de ce bassin versant, essentiellement composé d’un granite plus ou moins fracturé, ont été échantillonnées mensuellement sur une période de deux ans, le long d’un profil altitudinal. Ce bassin versant présente également l’avantage d’être équipé de trois forages profonds (allant jusqu’à 150 mètres de profondeur) qui ont permis de prélever à la fois les roches et les eaux profondes. Sur la base de l’interprétation géochimique des eaux, la connectivité des différents compartiments hydrologiques a été évaluée et un schéma de fonctionnement hydrogéochimique est proposé s’appuyant sur une bonne connaissance du contexte géologique. Enfin, un taux d’altération et un flux d’eau sont estimés à partir d’une modélisation de l’évolution du rapport isotopique de l’uranium (234U/238U) le long d’un trajet d’eau. L’originalité de cette étude est également de coupler cette approche de traçage géochimique avec une approche modélisatrice en utilisant le logiciel KIRMAT (Kinetic Reactions and Mass transport) qui intègre les équations des réactions géochimiques (dissolution/précipitation) et les équations de transport (1D). Il est ainsi possible de simuler le transport réactif d’une eau traversant la roche le long d’un certain trajet d’eau. Cette modélisation s’appuie sur la caractérisation minéralogique, des propriétés physiques des échantillons de roches prélevés le long des forages et sur les interprétations géochimiques des eaux. Ainsi, la modélisation de la composition chimique des eaux de sources et des eaux de forages a permis d’affiner la compréhension des processus d’altération, notamment le rôle des phases secondaires précipitées. Celle-ci permet également une meilleure compréhension des phénomènes de couplage entre les différents paramètres qui contrôlent la signature chimique des eaux à l’échelle du bassin versant. / The main goal of the present thesis is to better constrain the parameters that control weathering processes at a small catchment scale, focusing specifically on the role of hydrology. For this purpose, temporal and spatial variations of the chemical and isotopic (U, Sr) water composition of the Ringelbach catchment are studied. Several springs of this catchment whose basement is mainly composed of granite more or less fractured located along an altitudinal profile were monthly sampled over a period of two years. The additional interest of this site is that three deep boreholes (up to 150 meters deep) allow the sampling of both deep rocks and waters. The connectivity of the different hydrological compartments is evaluated based on the geochemical interpretation of water samples. A schematic hydrological functioning is proposed based on a good knowledge of the geological context. Finally, a weathering rate and a water flux are estimated from the modeling of the uranium activity ratio along a water path. The originality of this study lays also in combination of a geochemical and modeling approaches using the software KIRMAT (Kinetic Reactions and Mass transport) that integrates geochemical reactions (dissolution/precipitation) and 1D mass transport equations. It allow to simulate the reactive transport of a fluid through a rock along a given water pathway. This modeling is based on the characterization of the mineralogical and physical properties of the rock, sampled along the boreholes and the geochemical interpretation of the waters. Thus, the modeling of the chemical composition of the spring waters and borehole waters permit to improve the understanding of weathering processes including the role of precipitated secondary phases. It also allows to better understand the interplay of parameters that that control the water chemical signature at the catchment scale.

Nos últimos anos, a necessidade de melhorar o conhecimento dos recursos hídricos subterrâneos tem sido cada vez mais importante, justificando o elevado número de estudos que estão sendo desenvolvidos sobre o Sistema Aquífero Serra Geral (SASG). A área em estudo encontra-se na região Noroeste do Estado do Rio Grande do Sul abrangendo 107 municípios. Geologicamente a área é constituída por rochas vulcânicas da Formação Serra Geral, sendo o SASG, o aquífero mais utilizado na região. A região apresenta forte afetação de tectônica rúptil, cuja caracterização estrutural é importante para o entendimento da hidráulica e da distribuição hidrogeoquímica do sistema aquífero envolvido. O objetivo do presente estudo consiste na caracterização morfoestrutural, hidrogeológica e hidrogeoquímica do SASG, tentando reconhecer a influência da tectônica no potencial hidrogeológico e na disposição dos diferentes tipos hidrogeoquímicos de águas subterrâneas, testando a existência de relações com as estruturas no condicionamento do sistema aquífero, através dos dados obtidos de poços tubulares e do estudo dos lineamentos estruturais presentes na área. A metodologia utilizada envolveu a aquisição de dados de poços tubulares georreferenciados da região, traçado de lineamentos morfotectônicos por meio de imagens de satélite e filtragens em Sistema de Informações Geográficas (SIG), geração mapas temáticos e, por fim, uma análise estatística dos dados obtidos. Foram traçados 1.981 lineamentos tectônicos, sendo esses separados por comprimento e padrões de direções. A variação do potencial hidrogeológico demonstrou a influência das estruturas tectônicas regionais, onde se verificou uma correlação positiva entre a densidade de lineamentos com o potencial de produção dos poços. Os lineamentos de pequeno porte e de direções NE-E e NW-W são dominantes na área e são os padrões que apresentam estatisticamente maior potencial de produção dos poços. A variação das fácies hidrogeoquímicas demonstrou a influência das estruturas tectônicas regionais, onde se verificou uma correlação positiva entre a densidade de lineamentos com o as fácies estudadas. As Fácies CaMg e Águas Mistas apresentam características de baixo tempo de residência, estando mais relacionadas a captações de águas associadas a áreas de recarga do SASG, sendo a primeira relacionada aos lineamentos de direção NE-E e N-NW e a segunda com a direção NW-W. A Fácies Na, relacionada com lineamentos de direção NE-E e NW-W, apresenta valores de pH alcalinos, baixa dureza e elevado STD, que sugerem mistura com águas provenientes do SAG subjacente. As Fácies FeK e F estão mais relacionadas com zonas de recarga ascendente do SAG, sendo a primeira apresentando relação com as direções NE-E e NW-W e a segunda fortemente relacionada com lineamentos N-NE. / In the recent years, the need to improve the knowledge of groundwater resources has been increasingly important, justifying the large number of studies that are being developed on the Serra Geral Aquifer System (SGAS). The study area is located in the Alto Uruguai River region, northwest of the State of Rio Grande do Sul, covering 107 municipal districts. Geologically the area consists of volcanic rocks of the Serra Geral Formation, representing the SGAS, the most exploited aquifer in the region. The area is highly affected by tectonic lineaments, whose structural characterization is an important feature to better understanding the hydraulic and hydrogeochemical characteristics of this aquifer system. The aim of the present study includes the morphostructural, hydrogeological and hydrogeochemical characterization of the SGAS, recognizing the influence of tectonic lineaments on the hydrogeological potential and in the distribution of different hydrogeochemical facies. Through the database of tubular wells and the study of the morphotectonic lineaments present in the area, statistical tests were performed in order to find out structural relationships conditioning the aquifer system, The methodology used in the present study included the acquisition data of georeferenced tubular wells of the region, tracing of morphotectonic lineaments through satellite images, filtering in geographic information system (GIS) and statistical analysis using Principal Components Analysis and Cluster Analysis overall data. 1.981 lineaments were drawn and discriminated by length and direction patterns. Variations in the hydraulic capacity demonstrated the influence of regional tectonic structures. This is certified by the positive correlation between the lineament density and the water production of the wells. The small lineaments and directions NE-E and NW-W are dominant in the area and statistically are the most important factors for the potential production from the wells. The variation of hydrogeochemical facies showed the influence of regional tectonic structures, with a positive correlation between the lineaments density with the observed hydrochemical facies. The CaMg Facies and the Facies of Mixed Waters exhibit characteristics of low time residence, being related to recharge areas of SGAS, the first one mainly linked to NE-E and N-NW directions and the second one to the NW-W direction. The Na Facies is related to NE-E and NW-W lineaments, showing alkaline pH, low hardness and high Total Dissolved Solids, suggesting mixing with waters from the underlying Guarani Aquifer System (GAS). The FeK Facies and F are more related to areas of ascending recharge of GAS, the first one presenting relationship with the NE-E and NW-W directions and the second strongly related to N-NE lineaments.

Nos últimos anos, a necessidade de melhorar o conhecimento dos recursos hídricos subterrâneos tem sido cada vez mais importante, justificando o elevado número de estudos que estão sendo desenvolvidos sobre o Sistema Aquífero Serra Geral (SASG). A área em estudo encontra-se na região Noroeste do Estado do Rio Grande do Sul abrangendo 107 municípios. Geologicamente a área é constituída por rochas vulcânicas da Formação Serra Geral, sendo o SASG, o aquífero mais utilizado na região. A região apresenta forte afetação de tectônica rúptil, cuja caracterização estrutural é importante para o entendimento da hidráulica e da distribuição hidrogeoquímica do sistema aquífero envolvido. O objetivo do presente estudo consiste na caracterização morfoestrutural, hidrogeológica e hidrogeoquímica do SASG, tentando reconhecer a influência da tectônica no potencial hidrogeológico e na disposição dos diferentes tipos hidrogeoquímicos de águas subterrâneas, testando a existência de relações com as estruturas no condicionamento do sistema aquífero, através dos dados obtidos de poços tubulares e do estudo dos lineamentos estruturais presentes na área. A metodologia utilizada envolveu a aquisição de dados de poços tubulares georreferenciados da região, traçado de lineamentos morfotectônicos por meio de imagens de satélite e filtragens em Sistema de Informações Geográficas (SIG), geração mapas temáticos e, por fim, uma análise estatística dos dados obtidos. Foram traçados 1.981 lineamentos tectônicos, sendo esses separados por comprimento e padrões de direções. A variação do potencial hidrogeológico demonstrou a influência das estruturas tectônicas regionais, onde se verificou uma correlação positiva entre a densidade de lineamentos com o potencial de produção dos poços. Os lineamentos de pequeno porte e de direções NE-E e NW-W são dominantes na área e são os padrões que apresentam estatisticamente maior potencial de produção dos poços. A variação das fácies hidrogeoquímicas demonstrou a influência das estruturas tectônicas regionais, onde se verificou uma correlação positiva entre a densidade de lineamentos com o as fácies estudadas. As Fácies CaMg e Águas Mistas apresentam características de baixo tempo de residência, estando mais relacionadas a captações de águas associadas a áreas de recarga do SASG, sendo a primeira relacionada aos lineamentos de direção NE-E e N-NW e a segunda com a direção NW-W. A Fácies Na, relacionada com lineamentos de direção NE-E e NW-W, apresenta valores de pH alcalinos, baixa dureza e elevado STD, que sugerem mistura com águas provenientes do SAG subjacente. As Fácies FeK e F estão mais relacionadas com zonas de recarga ascendente do SAG, sendo a primeira apresentando relação com as direções NE-E e NW-W e a segunda fortemente relacionada com lineamentos N-NE. / In the recent years, the need to improve the knowledge of groundwater resources has been increasingly important, justifying the large number of studies that are being developed on the Serra Geral Aquifer System (SGAS). The study area is located in the Alto Uruguai River region, northwest of the State of Rio Grande do Sul, covering 107 municipal districts. Geologically the area consists of volcanic rocks of the Serra Geral Formation, representing the SGAS, the most exploited aquifer in the region. The area is highly affected by tectonic lineaments, whose structural characterization is an important feature to better understanding the hydraulic and hydrogeochemical characteristics of this aquifer system. The aim of the present study includes the morphostructural, hydrogeological and hydrogeochemical characterization of the SGAS, recognizing the influence of tectonic lineaments on the hydrogeological potential and in the distribution of different hydrogeochemical facies. Through the database of tubular wells and the study of the morphotectonic lineaments present in the area, statistical tests were performed in order to find out structural relationships conditioning the aquifer system, The methodology used in the present study included the acquisition data of georeferenced tubular wells of the region, tracing of morphotectonic lineaments through satellite images, filtering in geographic information system (GIS) and statistical analysis using Principal Components Analysis and Cluster Analysis overall data. 1.981 lineaments were drawn and discriminated by length and direction patterns. Variations in the hydraulic capacity demonstrated the influence of regional tectonic structures. This is certified by the positive correlation between the lineament density and the water production of the wells. The small lineaments and directions NE-E and NW-W are dominant in the area and statistically are the most important factors for the potential production from the wells. The variation of hydrogeochemical facies showed the influence of regional tectonic structures, with a positive correlation between the lineaments density with the observed hydrochemical facies. The CaMg Facies and the Facies of Mixed Waters exhibit characteristics of low time residence, being related to recharge areas of SGAS, the first one mainly linked to NE-E and N-NW directions and the second one to the NW-W direction. The Na Facies is related to NE-E and NW-W lineaments, showing alkaline pH, low hardness and high Total Dissolved Solids, suggesting mixing with waters from the underlying Guarani Aquifer System (GAS). The FeK Facies and F are more related to areas of ascending recharge of GAS, the first one presenting relationship with the NE-E and NW-W directions and the second strongly related to N-NE lineaments.