Research methods for seawater intrusion in China and recommendations for novel radium-radon technologies.

Seawater intrusion has been a globally significant environmental issue. This paper comprehensively reviews and highlights the research methods of seawater intrusion in China, recommending the potential application of novel radioactive radium-radon isotopes. Geochemical and geophysical techniques have been extensively utilized in studying seawater intrusion in China, including methods such as hydrochemical analysis, groundwater level observations, geophysical survey techniques, and isotope tracing. The former three methodologies boast a lengthier historical application in seawater intrusion field, while the radium-radon tools in isotope tracing, as newcomers, can specifically indicate crucial scientific questions such as seawater intrusion rates, salt groundwater age, water-rock reactions, and preferential flow dynamics. However, it is imperative to acknowledge the limitations inherent in the utilization of radium-radon tools within the realm of seawater intrusion research, as with any other methodologies. Strategic integration of radium-radon tools with other methodologies will propel advancements in the investigation of seawater intrusion in China. While the primary focus is on research methods in China, insights gained from novel radium-radon tools could have broader value for seawater intrusion research and coastal management globally.