DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Recharge sources and hydraulic communication of karst aquifer, São Miguel watershed, MG, Brazil.(2020) Lucon, Thiago Nogueira; Costa, Adivane Terezinha; Galvão, Paulo Henrique Ferreira; Leite, Mariangela Garcia Praça; Madeira, Thiago José Augusto; Nogueira, Leonardo BrandãoThe main public water supply in the São Miguel watershed (MG, Brazil) comes from a well-developed karst region, where information about hydraulic communications between caves entrances, sinkholes, recharge and discharge areas are still unknown. The study aims to identify regional hydrogeological processes describing groundwater hydrochemical evolution, interactions between meteoric, surface and ground waters, recharge and discharge sources, and possible hydraulic communications for proper management of water resources. Geophysical data were analyzed and water samples (meteoric, surface, and groundwater) throughout the watershed were collected for stable isotopes (18O and 2 H) and major ions analyzes. Results indicated strong influences of regional geological structures in the karst water flow directions; high concentrations of major ions in the central region of the watershed are common; karstification processes and aquifer recharge are more active during the rainy season, while in the dry season the watershed is supplied by groundwater.Item Cadmium behavior in a karst environment hydrological cycle.(2020) Lucon, Thiago Nogueira; Costa, Adivane Terezinha; Galvão, Paulo Henrique Ferreira; Leite, Mariangela Garcia PraçaKarst regions are important water providers, supplying approximately 25% of the world population. These areas present higher vulnerability to contamination due to hydrodynamics, which hampers the natural depuration of these waters until reaching the underground environment. High concentrations of cadmium (Cd) are observed in the São Miguel watershed, state of Minas Gerais, Brazil. This toxic element is generally and predominantly released into the atmosphere by burning materials that have Cd in their composition, potentially contaminating surface and groundwater. Therefore, the objective of the study is to map Cd concentrations in the hydrological cycle of the São Miguel karst watershed and, through natural background level values (NBL 90%) of rainwater, surface water and groundwater, to understand the seasonal behavior of this element, and to identify the most vulnerable areas to contamination. To achieve this goal, rainwater, surface, and groundwater seasonal monitoring were conducted in 87 sampling stations. A total of 335 samples were collected, distributed over a watershed area of 520 km2 . Concentrations of cadmium above 1 μg/L were found in 21.49% of samples during the rainy season. The origin and distribution of Cd were related to rainfall. For rainwater samples, 90% presented Cd concentration of 3.06 μg/L. When these waters precipitate, they contaminate surface waters (NBL 90% = 1.50 μg/L) and groundwater (NBL 90% = 2.81 μg/L). This study presented a hydrochemical cycle map and proposed NBL values of Cd for surface water and groundwater, helping to understand how the environment is contaminated by this element.Item Natural background levels and validation of the assessment of intrinsic vulnerability to the contamination in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil.(2020) Cardoso, Frederico Aragão; Velásquez, Leila Nunes Menegasse; Galvão, Paulo Henrique Ferreira; Tayer, Thiaggo de Castro; Lucon, Thiago Nogueira; Azevedo, Úrsula Ruchkys deThe contamination of karst aquifers by anthropogenic activities causes a major issue regarding environmental policies, since they present high sensitivity, influenced by unique features such as dolines, swallow holes, and conduits. This paper is focused on the Carste Lagoa Santa Protection Unit, MG, Brazil, and presents three main objectives: to determine the natural background levels of chloride, nitrate, sulfate, and phosphate; to indicate the locations where the concentrations of those parameters exceed the natural background levels in the existing vulnerability map and, finally, to determine the proportion of the areas (in percentage) where this surpassing occurs, according to the vulnerability classes (high, moderate and low). Results have shown values (90th percentile) of 2.4 mg/L, 1.0 mg/L, 5.3 mg/L, and 0.1 mg/L, for Cl−, NO3−, SO4−2, and PO4−3, respectively, indicating that for all four parameters, there were areas (mainly distributed within moderate vulnerability portions) where the values were surpassed, which suggests anthropogenic activity due to the presence of urban settlements and agricultural activities. Therefore, the proposal of natural background levels was essential to understand the hydrochemistry of the studied region.Item Comportamento hidrogeoquímico da região cárstica do Alto São Francisco (MG) : implicações associadas a sazonalidade e ciclo de contaminantes, áreas de recarga, descarga e comunicações hidráulicas(2018) Lucon, Thiago Nogueira; Leite, Mariangela Garcia Praça; Costa, Adivane Terezinha; Galvão, Paulo Henrique Ferreira; Leite, Mariangela Garcia Praça; Hoeser, Hubert Matias Peter; Santiago, Aníbal da Fonseca; Auler, Augusto Sarreiro; Karmann, IvoEste estudo visa compreender o comportamento e a qualidade das águas da bacia hidrográfica do rio São Miguel (≈520 km2), centro-oeste de Minas Gerais, afluente do rio São Francisco e inserida na bacia hidrográfica do Alto São Francisco (235.635 km2). A região abrange em sua maior parte os municípios de Pains e Arcos, seguida por áreas dos municípios de Iguatama, Formiga e Córrego Fundo. Para tanto, foi realizado um monitoramento hidroquímico sazonal das águas (meteóricas, superficiais e subterrâneas) em 89 pontos da bacia, durante dois períodos secos e dois chuvosos. As análises incluíram a determinação dos parâmetros físico-químicos, como temperatura, pH, Eh, condutividade elétrica (CE), sólidos totais dissolvidos (STD), oxigênio dissolvido e turbidez, assim como a concentração dos ânions nitrato (NO3-), fosfato (PO43-), bicarbonato (HCO3), sulfato (SO42-) e cloreto (Cl-), e cátions maiores e elementos menores, traço, terras raras e as assinaturasisotópicas de δ18O e δ2H. Com o auxílio estatístico, foram propostos valores de Natural Background Level - NBL 90% para os principais íons das águas da bacia. As águas analisadas foram classificadas predominantemente como cálcicas bicarbonatadas, apresentando os maiores valores de NBL 90% para o cálcio (Ca2+), potássio (K+), bicarbonato (HCO3), sulfato (SO42-), cloreto (Cl-), nitrato (NO3-) e arsênio (As3+) durante o período chuvoso; diferentemente, os elementos magnésio (Mg2+), sódio (Na+), fosfato (PO43-) e zinco (Zn) apresentaram decréscimo nesta mesma estação. Os valores acima de NBL 90% para NO3-, PO43- e Cl estão diretamente ligados à ação antrópica. Para o elemento cádmio (Cd), verificou-se que as concentrações mais elevadas deste elemento entram na bacia a partir de águas meteóricas, contaminando posteriormente as águas superficiais e subterrâneas. O estudo apresenta de forma inédita todo o funcionamento hidrodinâmico da bacia cárstica em estudo, apontando com apoio das assinaturas isotópicas para o δ18O e δ2H, as áreas de recarga e descarga, além da identificação das redes de fluxo e interconexões hidráulicas subterrâneas. O estudo fez uso de diversas ferramentas que se mostram indispensáveis para subsidiar a gestão dos recursos hídricos em áreas cársticas, podendo os resultados serem utilizados pelo poder público como valores de referência para regiões cársticas semelhantes, além de ajudar a compreender o comportamento hidroquímico, principalmente para os elementos de elevada toxicidade.Item Natural background levels and seasonal influence on groundwater chemistry of the Upper São Francisco karst region, MG, Brazil.(2018) Lucon, Thiago Nogueira; Costa, Adivane Terezinha; Galvão, Paulo Henrique FerreiraKarst aquifers are large water reservoirs that supply approximately 25% of the world population. They are also extremely sensitive to contamination, demanding knowledge on groundwater quality regarding base level conditions for the main cations and anions. Knowing the Natural Background Level (NBL) values of these waters becomes an indispensable measure to understand aquifers and hydrochemical anomalies, either from anthropogenic or geogenic origin. This paper aimed to provide a hydrochemical characterization and to propose NBL 90% values for the little-studied groundwater of the São Miguel River watershed, Upper São Francisco River, MG, Brazil. NBL 90% values were estimated using statistical analyses followed by an analysis of seasonal influence on observed concentrations. The water was classified as calcium bicarbonate, with the highest NBL 90% values occurring during the rainy season for Ca2+, K+, HCO3 -, SO4 2-, Cl-, NO3 -, and As3+. On the other hand, Mg2+, Na+, PO4 3-, and Zn2+ presented reduction in concentration during this season. Nitrate, phosphate and chloride anomalies (values above NBL 90%) are directly related to human action. Thus, monitoring and proposing NBL 90% values were an essential tool to help in understanding the hydrochemical behavior of waters in this watershed.Item Adapting the EPIK method to Brazilian Hydro(geo)logical context of the São Miguel watershed to assess karstic aquifer vulnerability to contamination.(2018) Pereira, Débora Lara; Galvão, Paulo Henrique Ferreira; Lucon, Thiago Nogueira; Fujaco, Maria Augusta GonçalvesKarst aquifers are, besides important strategic reservoirs of good quality water, heterogeneous and anisotropic, where highly permeable karst networks result in insufficient time for contaminant degradations, and hence the quasi-immediate contamination of the aquifer. The EPIK method is a low-cost technique and was developed to map karst regions based on four main feature indexes: 1) epikarst; 2) protective cover; 3) infiltration conditions; and 4) karst network development. However, the method was developed according to European hydrogeologic and temperate climatic contexts, where its application without adaptations in regions in different contexts may result in possible misunderstandings, such as overlook, underestimate or overestimate significances of some parameters (e.g. soil covers, rainfall regimes, morphological domains). The Brazilian São Miguel watershed, a tropical karst region where the city of Pains is located (southwestern Minas Gerais), is characterized by high levels of thermotolerant coliforms, phosphorus, nitrate, and cadmium in surface water and groundwater. These contaminants come from, agriculture, livestock, and urban areas. Due to these issues and to provide a tool of water resource management and land use planning, the EPIK method was adapted to the hydrogeologic reality of the São Miguel watershed, considering both local vegetation and the current Brazilian speleological heritage protection legislation. Results revealed that 52% of the area has moderate vulnerability and 7% high vulnerability, this latter one concentrated in areas close to mining activities and urban areas. The study provided a reliable map and adapted technique which can be used in other Brazilian karst regions and other tropical karst regions.