George et al. (2026) Submarine groundwater discharge and associated fluxes along the Kanyakumari coast of India using radon and nutrient mass balance approach

Identification

• Journal: Scientific Reports
• Year: 2026
• Date: 2026-03-11
• Authors: Annmaria K. George, M. Suresh Gandhi, P. Muthukumar, Priyadarsi D. Roy, A. Baalamurugan, Muralitharan Jothimani, S. Selvam
• DOI: 10.1038/s41598-026-37950-9

Research Groups

• Department of Geology, University of Madras Guindy campus, Chennai, India
• Department of Geology, V.O. Chidambaram College, Thoothukudi, Tamil Nadu, India
• Instituto de Geología, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, Mexico
• Department of Geology, College of Natural and Computational Sciences, Arba Minch University, Arba Minch, Ethiopia

Short Summary

This study quantified submarine groundwater discharge (SGD) and associated nutrient fluxes along the Kanyakumari coast of India using radon and nutrient mass balance approaches, revealing significant seasonal variations influenced by monsoonal recharge and tidal dynamics.

Objective

• To estimate submarine groundwater discharge (SGD) and associated dissolved inorganic nutrient (nitrogen, phosphorus, and silicate) fluxes along the Kanyakumari coast of India.
• To utilize radon (²²²Rn) and nutrient mass balance approaches to understand the influence of SGD on coastal nutrient dynamics and water quality, and to demarcate areas of major discharge.

Study Configuration

• Spatial Scale: Kanyakumari coast of India (8°10’–8°15’N latitude, 77°10’–77°20’E longitude).
• Temporal Scale: Pre-monsoon (May 2023) and Post-monsoon (January 2024) seasons, considering high-tide and low-tide conditions.

Methodology and Data

• Models used: Radon (²²²Rn) mass balance approach, Nutrient mass balance approach.
• Data sources:
  • Fifty-eight water samples (29 groundwater, 29 porewater) collected from inland wells and intertidal zones.
  • In-situ measurements of pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Temperature, and Salinity using a portable water quality analyzer.
  • Radon (²²²Rn) analysis performed using a RAD7 instrument (Durridge Company Inc.).
  • Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP), and Dissolved Silicate (DSi) concentrations measured using a double-beam UV–VIS spectrophotometer (Model 2203, Systronics).

Main Results

• Radon (²²²Rn) concentrations ranged from 11.68 to 66.96 Bq/L during pre-monsoon and 18.9 to 189.56 Bq/L during post-monsoon, showing an inverse relationship with EC.
• Estimated SGD flux ranged from 0.01 to 0.54 m³m⁻²d⁻¹ in pre-monsoon and 0.03 to 1.02 m³m⁻²d⁻¹ in post-monsoon, indicating enhanced discharge during the post-monsoon due to monsoonal recharge.
• Mean nutrient concentrations for DIN, DIP, and DSi were 2, 0.21, and 20.75 µmol/L, respectively, during pre-monsoon, and 0.79, 0.28, and 17.22 µmol/L, respectively, during post-monsoon.
• Pre-monsoon conditions favored higher nutrient accumulation (DIN, DSi), while post-monsoon conditions promoted dilution.
• Freshwater SGD was primarily confined to the northern portion of the study area (Enayam beach), influenced by coastal geomorphology, permeability, and tidal forcing.

Contributions

• Provided the first detailed quantitative evaluation of Submarine Groundwater Discharge (SGD) along the Kanyakumari coast of India using a combined radon and nutrient mass balance approach.
• Demarcated specific areas of major SGD discharge and highlighted their significant influence on coastal nutrient dynamics and water quality.
• Offered valuable data to inform methodologies for mitigating groundwater scarcity and pollution in the region.
• Demonstrated the critical impact of monsoonal recharge and tidal pumping on seasonal SGD dynamics and associated nutrient fluxes in a monsoon-influenced coastal system.

Funding

No funding is available for this study.

Citation

@article{George2026Submarine,
  author = {George, Annmaria K. and Gandhi, M. Suresh and Muthukumar, P. and Roy, Priyadarsi D. and Baalamurugan, A. and Jothimani, Muralitharan and Selvam, S.},
  title = {Submarine groundwater discharge and associated fluxes along the Kanyakumari coast of India using radon and nutrient mass balance approach},
  journal = {Scientific Reports},
  year = {2026},
  doi = {10.1038/s41598-026-37950-9},
  url = {https://doi.org/10.1038/s41598-026-37950-9}
}