Bedrock aquifers are vulnerable to contamination due to the preferential movement of pollutants via rock discontinuities and porous layers. In this research, we propose an approach to assess vulnerability in three dimensions by combining stable isotope values and particle tracking in a vertically anisotropic aquifer of basaltic-fluvial origin at the basin-scale. A steady-state flow and particle tracking model is presented for the Columbia River Basalt aquifer in the South Fork Palouse Basin. Backward particle analysis combined with the distribution of δ²H, δ¹⁸O and ⁴He values vs. depth shows how the aquifer is characterized by two separated zones. A shallow (< 150 mBGL) aquifer portion is characterized by low particle travel times from the pumping wells to the recharge boundaries. However, the deeper (> 150 mBGL) aquifer zone is characterized by much higher particle travel times as well as a distinctive isotopic fingerprint. At such depths, penetration of particles is partially impeded by the low hydraulic conductivity of the sedimentary layers and recharge preferentially occurs in correspondence of the basin margin. Along this margin, the vulnerability is higher for the contaminants to enter the aquifer system and reach the pumping wells. Thus, following this research, we envisage efforts to combine stable isotope techniques with particle tracking analysis in three dimensions to define areas exposed to contamination risk in fluvio-volcanic bedrock aquifers. These research efforts can represent an approach to integrate with two-dimensional GIS tools that are commonly used to assess aquifer vulnerability.

基岩含水层易受污染，原因是污染物通过岩石间断和多孔层优先移动。在这项研究中，我们提出了一种方法，通过在盆地规模的玄武质-河流相垂直垂直各向异性含水层中结合稳定的同位素值和颗粒追踪，在三个维度上评估脆弱性。提出了南福尔帕洛斯盆地哥伦比亚河玄武岩含水层的稳态流和颗粒跟踪模型。向后颗粒分析与δ的分布组合² H，δ ¹⁸ O和⁴他的值与深度的关系说明了含水层如何通过两个分离的区域来表征。浅层（<150 mBGL）的含水层的特征是从抽水井到补给边界的颗粒传播时间短。但是，较深的（> 150 mBGL）含水层区域的特征是更长的粒子传播时间以及独特的同位素指纹。在这样的深度，沉积层的低水力传导率会部分阻止颗粒的渗透，并且对应于盆地边缘，优先发生补给。沿着这个界限，污染物进入含水层系统并到达抽水井的脆弱性更高。因此，根据这项研究，我们设想将稳定同位素技术与三个维度的颗粒跟踪分析相结合，以定义在火山岩基岩含水层中暴露于污染风险的区域。这些研究工作可以代表一种与二维GIS工具集成的方法，该工具通常用于评估含水层的脆弱性。