Groundwater dynamics on small carbonate islands: Insights from radiocarbon and stable isotopes in Kikai Island, Southwest Japan.

Groundwater, the world's largest freshwater resource, faces significant challenges due to the overexploitation and depletion of aquifers in the 21st century. Small island groundwater aquifers are particularly valuable, and a scientific understanding of the behavior of subsurface water systems is vital. A comprehensive study using radiocarbon, stable oxygen isotopes, stable hydrogen isotopes, and hardness analysis (ΔC, δO, δD, Ca, Mg) of groundwater was conducted in Kikai Island, a southern island in the Amami archipelago, Japan.