ABSTRACT In 2015 and 2016, groundwater samples were collected in Hanoi to analyse the isotopic composition (δ2H, δ18O and 3H) and elucidate the relationship between groundwater and surface water, as well as the origin of the groundwater. The values for δ18O and δ2H indicate that the groundwater originated from evaporated meteoric water and the isotope enrichment is due to the evaporation of shallow groundwater. Evaporation is the primary process affecting stable isotope signatures. Water samples collected from both Holocene and Pleistocene aquifers are more depleted in the heavy isotopes 18O and 2H than the rainfall in the area. This indicates that part of the groundwater is paleo-groundwater or may be caused by the altitude effect due to recharge at a higher elevation. The results also show the close interaction between two granular aquifers and the Red River. Furthermore, the contribution of modern groundwater could be observed by the appearance of tritium in both aquifers. The presence of tritium indicates that originally tritium-free groundwater from the margins of the basin has been diluted by young water. The results of this study might help managers to evaluate the origin and reserves of groundwater more accurately.

中文翻译：

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环境同位素揭示越南河内地下水的来源

摘要 2015 年和 2016 年在河内采集地下水样品，分析同位素组成（δ2H、δ18O 和 3H），阐明地下水与地表水的关系，以及地下水的来源。δ18O 和 δ2H 值表明地下水来源于蒸发的大气水，同位素富集是由于浅层地下水的蒸发。蒸发是影响稳定同位素特征的主要过程。从全新世和更新世含水层收集的水样中重同位素 18O 和 2H 比该地区的降雨量更耗尽。这说明部分地下水为古地下水或可能是由于高海拔补给的海拔效应所致。结果还显示了两个颗粒状含水层与红河之间的密切相互作用。此外，可以通过两个含水层中氚的出现来观察现代地下水的贡献。氚的存在表明盆地边缘最初不含氚的地下水已被年轻水稀释。这项研究的结果可能有助于管理者更准确地评估地下水的来源和储量。