ABSTRACT The stable isotopes of oxygen and hydrogen can provide useful insights into water origin and hydrological processes. The present study aims to investigate the characteristics of stable H/O isotopes of groundwater and surface water in a coastal area of the Vietnamese Mekong Delta. Isotopes and chloride concentrations of surface water show a highly seasonal and linearly spatial variability, depending on the distance to the sea. The seasonal variation of upstream discharge and rainfall plays an important role in changes of the isotopic compositions and chloride concentrations. Tide also influences on chloride concentrations of surface water while it does not change the isotopic compositions. Evaporation plays a crucial role in changes of isotopic compositions, while the influence of freshwater/seawater mixing on isotopic variabilities is negligible. Groundwater has a spatial heterogeneity in isotopic compositions and chloride concentrations, reflecting different recharge sources and seawater intrusion processes. Groundwater in shallow aquifers originates from rainfall and surface water with small evaporative losses, and it experienced different magnitudes of mixing with seawater. Groundwater in deep aquifers might be recharged by open-surface water evaporation in the last glacial age with minor impacts of seawater intrusion on these aquifers.

中文翻译：

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越南湄公河三角洲沿岸地区水资源稳定同位素特征

摘要 氧和氢的稳定同位素可以为水源和水文过程提供有用的见解。本研究旨在调查越南湄公河三角洲沿海地区地下水和地表水的稳定 H/O 同位素特征。地表水的同位素和氯化物浓度显示出高度的季节性和线性空间变化，这取决于与海洋的距离。上游流量和降雨的季节性变化对同位素组成和氯化物浓度的变化起着重要作用。潮汐也会影响地表水中的氯化物浓度，但不会改变同位素组成。蒸发在同位素组成的变化中起着至关重要的作用，而淡水/海水混合对同位素变异的影响可以忽略不计。地下水在同位素组成和氯化物浓度方面具有空间异质性，反映了不同的补给源和海水入侵过程。浅层含水层地下水来源于降雨和地表水，蒸发损失小，与海水混合程度不同。深部含水层中的地下水可能会通过最后一个冰河时代的开放地表水蒸发进行补给，海水入侵对这些含水层的影响较小。浅层含水层地下水来源于降雨和地表水，蒸发损失小，与海水混合程度不同。深部含水层中的地下水可能会通过最后一个冰河时代的开放地表水蒸发进行补给，海水入侵对这些含水层的影响较小。浅层含水层地下水来源于降雨和地表水，蒸发损失小，与海水混合程度不同。深部含水层中的地下水可能会通过最后一个冰河时代的开放地表水蒸发进行补给，海水入侵对这些含水层的影响较小。