ABSTRACT The Tubarão aquifer system constitutes a very complex, multilayered aquifer enclosed in the Paraná basin (central-southern part of Brazil). Despite the relatively low productivity of wells, groundwater represents an important source of water for the very populated and industrialized zones of the State of São Paulo. An extensive water sampling campaign was carried out followed by hydrochemical and isotopic (δ 2H, δ 18O, δ 13C and 14C) studies, aiming at a better understanding of the aquifer's geochemical evolution, recharge processes, and its groundwater residence times. Two main hydrochemical facies were recognized and divide the aquifer in two portions. The shallow portion – the active hydrological zone of the aquifer – is characterized by the Ca-HCO3 water type, evolving as a system open to atmospheric CO2. Mean residence times are typically lower than 5000 years. The lower portion is mostly characterized by the stagnant, Na-HCO3 water type, evolving under closed system conditions. Residence times average up to 15,000 years, but can reach 44,000 years, which indicates the exploitation of (possibly non-renewable) fossil waters. This study contributes to the establishment of proper policies regarding the sustainable groundwater exploitation of the Tubarão aquifer system.

中文翻译：

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水化学、稳定同位素和 14C 数据表明的多层图巴朗含水层系统（圣保罗州 - 巴西）的地球化学演化、停留时间和补给条件

摘要 Tubarão 含水层系统构成了一个非常复杂的多层含水层，封闭在巴拉那盆地（巴西中南部）中。尽管水井的生产力相对较低，但地下水是圣保罗州人口稠密和工业化地区的重要水源。进行了广泛的水采样活动，随后进行了水化学和同位素（δ 2H、δ 18O、δ 13C 和 14C）研究，旨在更好地了解含水层的地球化学演化、补给过程及其地下水停留时间。识别出两个主要的水化学相并将含水层分为两部分。浅层部分——含水层的活跃水文区——以 Ca-HCO3 水类型为特征，演变为一个对大气 CO2 开放的系统。平均停留时间通常低于 5000 年。下部的主要特征是停滞的 Na-HCO3 水类型，在封闭系统条件下演变。停留时间平均长达 15,000 年，但可以达到 44,000 年，这表明（可能是不可再生的）化石水的开采。这项研究有助于制定有关图巴朗含水层系统可持续地下水开发的适当政策。