Groundwater flow and the geochemical evolution of a freshwater lens in an aquifer on a Pacific atoll were investigated by hydrogeochemical surveys. Sulfur hexafluoride measurements showed that deeper groundwater and groundwater at the periphery of the lens are older, consistent with a downward and outward groundwater flow scheme. This is the typical flow scheme on Pacific atolls where a Holocene–Pleistocene unconformity restricts the shape of the freshwater lens. Enrichment of Mg/Ca in the groundwater is another indicator of a longer residence time, because contact between the groundwater and the carbonate sediments composing the aquifer leads to the release of Mg from high-Mg calcite and the precipitation of Ca as low-Mg calcite. Groundwater quality was also affected by anthropogenic nitrogen loading and aboveground organic matter, which were altered by denitrification and sulfate reduction in the aquifer, especially in the older groundwater. The chemical composition of the groundwater in the center of the island, where saline water is up-coning, implies that freshwater recharge dilutes the older saline water, which as time passes will eventually be replaced by newly recharged freshwater.

通过水文地球化学调查研究了太平洋环礁上含水层中的地下水流量和淡水晶状体的地球化学演化。六氟化硫的测量结果表明，较深的地下水和晶状体外围的地下水年龄较大，与地下水的向下和向外流动方案一致。这是太平洋环礁的典型流向，其中全新世-更新世不整合限制了淡水晶状体的形状。地下水中Mg / Ca的富集是停留时间更长的另一个指标，因为地下水与构成含水层的碳酸盐沉积物之间的接触会导致Mg从高镁方解石中释放出来，而Ca沉淀为低镁方解石。地下水质量还受到人为氮负荷和地上有机质的影响，在含水层中，特别是在较老的地下水中，反硝化作用和硫酸盐还原作用改变了这些变化。该岛中心（盐水不断上升）的地下水的化学成分意味着淡水补给稀释了较旧的盐水，随着时间的流逝，咸水最终将被新补给的淡水所代替。