A pulsed ionization chamber (PIC) system for robust and efficient radon measurements in aquatic environments

As a naturally occurring radioisotope, radon (²²²Rn) has been routinely used to trace submarine groundwater discharge (SGD) in coastal regions and to study other oceanographic processes such as air‑sea gas exchange and sediment‑water diffusion. To enable rapid and accurate radon measurements, we have developed and refined several measurement technologies and approaches based on a self‑designed pulsed ionization chamber (PIC) radon detector. Because the PIC can collect and detect most alpha‑particle‑generated electric signals, its absolute detection efficiency is less affected by humidity and is generally higher than that of semiconductor‑ or scintillation‑based radon detectors. In addition to conventional surface‑water radon surveys, the PIC can be deployed on unmanned vessels and subsurface buoys for in‑situ underwater radon monitoring. The system also readily adapts to other applications, including measuring ²²⁶Ra and ²²⁴Ra activities in water samples and assessing ²²⁴Ra/²²⁸Th disequilibrium in sediments. This versatility and robustness position the PIC as a promising tool for advancing field‑based radon measurements across diverse aquatic settings, potentially opening new avenues for real‑time environmental monitoring and process‑oriented studies.