Assessing coastal groundwater risks from nuclear-contaminated water discharge under extreme drought and sustainable...

Nuclear-contaminated water discharge from the Fukushima Daiichi Nuclear Power Plant in Japan has raised concerns about seawater quality and potential environmental risks on coastal groundwater systems, especially in densely populated urban regions. This study develops a radionuclide decay and transport model tailored to Shanghai's hydrogeological conditions to assess the combined impacts of nuclear discharge, extreme drought, and Managed Aquifer Recharge (MAR) on groundwater quality. Under extreme drought conditions, lowered groundwater levels exacerbate seawater intrusion, intensifying seawater-groundwater interactions and leading to elevated radionuclide concentrations compared to normal scenarios. After 30 years of continuous discharge, concentrations of ¹³⁷Cs and ⁹⁰Sr at 160 m depth in Shanghai's aquifer increase by 33.93% and 46.40% under the assumed input scenario, respectively. Implementation of MAR demonstrates remarkable effectiveness, reducing radionuclide concentrations by up to 99.58% for ¹³⁷Cs and 99.10% for ⁹⁰Sr relative to non-MAR scenarios. Our findings highlight the critical role of proactive, nature-based interventions like MAR in mitigating nuclear contamination risks, enhancing the resilience and sustainability of coastal groundwater resources. This integrated modeling approach provides useful insights into coupled ocean-land water system behavior under climate stressors, and supports improved understanding for long-term environmental risk assessment and water resource management.