Sulfur hexafluoride (SF₆) is an established tracer for use in managed aquifer recharge projects. SF₆ exsolves from groundwater when it encounters trapped air according to Henry's law. This results in its retardation relative to groundwater flow, which can help determine porous media saturation and flow dynamics. SF₆ and the conservative, nonpartitioning tracer, bromide (Br⁻ added as KBr), were introduced to recharge water infiltrated into stacked glacial aquifers in Thurston County, Washington, providing the opportunity to observe SF₆ partitioning. Br⁻, which is assumed to travel at the same velocity as the groundwater, precedes SF₆ at most monitoring wells (MWs). Average groundwater velocity in the unconfined aquifer in the study area ranges from 3.9 to 40 m/d, except in the southwestern corner where it is slower. SF₆ in the shallow aquifer exhibits an average retardation factor of 2.5 ± 3.8, suggesting an air‐to‐water ratio on the order of 10⁻³ to 10⁻² in the pore space. Notable differences in tracer arrival times at adjacent wells indicate very heterogeneous conductivity. One MW exhibits double peaks in concentrations of both tracers with different degrees of retardation for the first and second peaks. This suggests multiple flowpaths to the well with variable saturation. The confining layer between the upper two aquifers appears to allow intermittent connection between aquifers but serves as an aquitard in most areas. This study demonstrates the utility of SF₆ partitioning for evaluating hydrologic conditions at prospective recharge sites.

中文翻译：

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六氟化硫和溴化钾作为地下水示踪剂，用于受控含水层补给

六氟化硫（SF ₆）是已建立的示踪剂，可用于有管理的含水层补给项目。根据亨利定律，SF ₆遇困空气时会从地下水中溶解。这导致其相对于地下水流动的滞后性，可以帮助确定多孔介质的饱和度和流动动力学。SF ₆和保守，nonpartitioning示踪剂，溴（溴^-加入溴化钾），被引入到渗透到在瑟斯顿县，华盛顿堆叠冰含水层补给水，从而提供机会观察SF ₆分区。BR ^- ，其被假定为行驶在相同的速度为地下水，先于SF ₆在大多数监测井（兆瓦）。除西南角较慢的区域外，研究区无限制含水层的平均地下水速度范围为3.9至40 m / d。浅层含水层中的SF ₆平均延迟系数为2.5±3.8，表明空水比约为10 ^-3到10 ^-2在毛孔空间。示踪剂到达相邻井的时间的显着差异表明电导率非常不均匀。一个兆瓦在两个示踪剂的浓度上均表现出双峰，其中第一峰和第二峰的延迟程度不同。这表明饱和度可变的井的多条流径。上部两个含水层之间的限制层似乎允许含水层之间的间歇性连接，但在大多数区域中都充当了水隔层。这项研究证明了SF ₆分配在评估预期补给地点的水文条件方面的实用性。