Urban groundwater management requires a thorough and robust scientific understanding of flow and transport processes. ³H/³He apparent ages have been shown to efficiently help provide important groundwater-related information. However, this type of analysis is expensive as well as labor- and time-intensive, and hence limits the number of potential sampling locations.

To overcome this limitation, we established an inter-relationship between ³H/³He apparent groundwater ages and ⁴He concentrations analyzed in the field with a newly developed portable gas equilibrium membrane inlet mass spectrometer (GE-MIMS) system, and demonstrated that the results of the simpler GE-MIMS system are an accurate and reliable alternative to sophisticated laboratory based analyses. The combined use of ³H/³He lab-based ages and predicted ages from the ³H/³He–⁴He age relationship opens new opportunities for site characterization, and reveals insights into the conceptual understanding of groundwater systems.

For our study site, we combined groundwater ages with hydrochemical data, water isotopes (¹⁸O and ²H), and perchloroethylene (PCE) concentrations (1) to identify spatial inter-aquifer mixing between artificially infiltrated groundwater and water originating from regional flow paths and (2) to explain the spatial differences in PCE contamination within the observed groundwater system. Overall, low PCE concentrations and young ages occur when the fraction of artificially infiltrated water is high. The results obtained from the age distribution analysis are strongly supported by the information gained from the isotopic and hydrochemical data. Moreover, for some wells, fault-induced aquifer connectivity is identified as a preferential flow path for the transport of older groundwater, leading to elevated PCE concentrations.

城市地下水管理需要对流动和运输过程有透彻而牢固的科学理解。³ H / ³他的明显年龄已被证明可以有效地提供重要的地下水相关信息。但是，这种类型的分析既昂贵又费力且费时，因此限制了潜在采样位置的数量。

为克服此限制，我们使用新开发的便携式气体平衡膜入口质谱仪（GE-MIMS）系统在现场分析了³ H / ³ He的表观地下水年龄与⁴ He浓度之间的相互关系，并证明了简单的GE-MIMS系统的结果是精确，可靠的替代方案，可替代基于实验室的复杂分析。结合使用³ H / ³他基于实验室的年龄和预测年龄从³ H / ³氦⁴他年龄的关系打开了场地特征的新机遇，揭示见解地下水系统的概念性理解。

在我们的研究地点，我们将地下水年龄与水化学数据，水同位素（¹⁸ O和²H）和全氯乙烯（PCE）浓度（1）识别人工渗透的地下水与区域流动路径产生的水之间的含水层间混合，以及（2）解释所观察到的地下水系统内PCE污染的空间差异。总体而言，当人工渗透的水比例较高时，PCE浓度较低且年龄较小。从年龄分布分析获得的结果得到同位素和水化学数据的大力支持。此外，对于某些井，断层诱发的含水层连通性被确定为优先运输较旧地下水的流动路径，从而导致PCE浓度升高。