Variação espaço-temporal da composição isotópica das águas subterrâneas de um aquífero basáltico, e sua implicação na construção de um modelo de fluxo, na Bacia Hidrográfica do Paraná 3.
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Data
2022-04-01
Autores
Garpelli, Lia Nogueira [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Compreender as condições climáticas e as suas relações com as águas que recarregam os aquíferos é primordial para uma gestão pública mais correta. Na região da Bacia do Paraná 3, no oeste do estado do Paraná, ocorrem rochas vulcânicas que caracterizam o Sistema Aquífero Serra Geral (SASG), amplamente utilizado pelas companhias de abastecimento do estado. A utilização de traçadores ambientais, como isótopos de oxigênio e deutério, auxiliam na compreensão das origens das águas, e dos fluxos das águas subterrâneas em aquíferos como o SASG. O estudo consistiu em coletas trimestrais de 35 amostras de poços tubulares, uma cacimba e coletas em três locais distintos do rio Lopeí, iniciadas em abril de 2019, até janeiro de 2020, além de coletas mensais de recipitação (de maio de 2019 a dezembro de 2020). Foram realizadas análises físico-químicas, medidas in situ, análises hidroquímicas dos principais cátions e ânions e a caracterização isotópica de oxigênio e deutério. Os resultados obtidos permitiram a caracterização climática e isotópica da precipitação, água superficial e subterrânea. As chuvas com variação de -9,02 a 0,24‰ (δ18O) e de -57,92 a 16,56‰ (δ2H), apresentaram os valores mais depletados nos períodos de maior incidência de chuva que culminaram com o fim da primavera e início do verão, com característico efeito quantidade e, os valores mais enriquecidos, nos períodos de menor umidade relativa e pluviosidade, típicos do inverno. As águas superficiais variaram o δ18O de -5,28 a -4,83‰, de -29,46 a -26,39‰ para δ2H, e apresentaram efeito altitude de 0,21‰ a cada 100 m de altitude. As águas subterrâneas com variação isotópica que foi de -5,81 a -4,30‰ e de -34,06 a -24,29‰, para δ18O e δ2H, respectivamente. Possuem três fácies hidroquímicas distintas, o grupo 1, do tipo Ca-Mg-HCO3, que representa a porção intermediária entre os dois grupos, indicativo de mistura de águas; o grupo 2, do tipo Ca-Mg-HCO3 com NO3 que representa águas de porções mais rasas com recargas pluviais recentes, e valores da composição isotópica mais enriquecidos e; o grupo 3, com tipologia Na-HCO3, que são marcadas por águas de fluxo mais profundo, com características de águas mais evoluídas hidroquimicamente e assinaturas isotópicas com valores mais depletados.
Understanding the climatic conditions and their relationship with the waters that recharge aquifers is essential for a better water public management. In the Paraná Basin 3 region, in the west of the state of Paraná, there are volcanic rocks which characterize the Serra Geral Aquifer System (SASG), widely used by the state’s water supply companies. The use of environmental tracers, such as oxygen and deuterium isotopes, assists the understanding of the origins of water and groundwater flows in aquifers such as the SASG. The study consisted of quarterly collection of 35 water well samples, a domestic water well and sampling in three different locations on the Lopeí River, started in April 2019 until January 2020, besides to monthly rain sampling (from May 2019 to December 2020). It was carried out physicochemical analyses, in situ measurements, hydrochemical analyzes of the main cations and anions, and oxygen and deuterium isotopic characterization. The results obtained allowed the climatic and isotopic characterization of precipitation. Rains with a variation from -9.02 to 0.24‰ (δ18O) and from -57.92 to 16.56‰ (δ2H), presented the most depleted values in periods of higher rainfall that culminated in late spring and early summer, with a characteristic quantity effect. During winter, the most enriched values, related to periods of lower relative humidity and rainfall. The surface water δ18O varied from -5.28 to -4.83‰, δ2H from -29.46 to a -26.39‰, and showed an altitude effect of 0.21‰ of every 100 m of altitude. Groundwater with isotopic variation ranging from -5.81 to -4.30‰ and from -34.06 to -24.29‰ for δ18O and δ2H respectively. There are three distinct hydrochemical facies, group 1, of the Ca-Mg-HCO3 type, which represents the intermediate portion between the two groups, indicative of water mixture; group 2, of the Ca-Mg-HCO3 with NO3 type, which represents water from shallower portions with recent rain recharge, and isotopic compositions with more enriched values; group 3, with Na-HCO3 typology, which is marked by deeper flowing waters, with more hydrochemically evolved water characteristics and isotopic signature with more depleted values.
Understanding the climatic conditions and their relationship with the waters that recharge aquifers is essential for a better water public management. In the Paraná Basin 3 region, in the west of the state of Paraná, there are volcanic rocks which characterize the Serra Geral Aquifer System (SASG), widely used by the state’s water supply companies. The use of environmental tracers, such as oxygen and deuterium isotopes, assists the understanding of the origins of water and groundwater flows in aquifers such as the SASG. The study consisted of quarterly collection of 35 water well samples, a domestic water well and sampling in three different locations on the Lopeí River, started in April 2019 until January 2020, besides to monthly rain sampling (from May 2019 to December 2020). It was carried out physicochemical analyses, in situ measurements, hydrochemical analyzes of the main cations and anions, and oxygen and deuterium isotopic characterization. The results obtained allowed the climatic and isotopic characterization of precipitation. Rains with a variation from -9.02 to 0.24‰ (δ18O) and from -57.92 to 16.56‰ (δ2H), presented the most depleted values in periods of higher rainfall that culminated in late spring and early summer, with a characteristic quantity effect. During winter, the most enriched values, related to periods of lower relative humidity and rainfall. The surface water δ18O varied from -5.28 to -4.83‰, δ2H from -29.46 to a -26.39‰, and showed an altitude effect of 0.21‰ of every 100 m of altitude. Groundwater with isotopic variation ranging from -5.81 to -4.30‰ and from -34.06 to -24.29‰ for δ18O and δ2H respectively. There are three distinct hydrochemical facies, group 1, of the Ca-Mg-HCO3 type, which represents the intermediate portion between the two groups, indicative of water mixture; group 2, of the Ca-Mg-HCO3 with NO3 type, which represents water from shallower portions with recent rain recharge, and isotopic compositions with more enriched values; group 3, with Na-HCO3 typology, which is marked by deeper flowing waters, with more hydrochemically evolved water characteristics and isotopic signature with more depleted values.
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Palavras-chave
Aquífero Serra Geral, BP3, Isótopos ambientais, Fácies hidroquímicas, Serra Geral aquifer, Environmental isotopes, Hydrochemical facies