Submarine groundwater discharge and associated fluxes along the Kanyakumari coast of India using radon and nutrient mass balance approach

Submarine groundwater discharge (SGD) acts as a carrier for elements, nutrients and pollutants into the ocean. This study estimated SGD along the Kanyakumari coast of India, using the Radon and nutrient mass balance approach. Groundwater and porewater samples during the high-tide and low-tide conditions showed Radon (222Rn) concentrations between 11.68 and 66.96 Bq/L during the pre-monsoon and between 18.9 and 189.56 Bq/L during the post-monsoon, with an inverse relationship with EC (256–52400 µS/cm: pre-monsoon and 329–48000 µS/cm: post-monsoon). SGD, estimated using the radon mass balance approach, ranged from 0.01 to 0.54 m3m−2d−1 in pre-monsoon and 0.04 to 0.98 m3m−2d−1 in post-monsoon. Mean nutrient concentrations for DIN, DIP, and DSi in both seasons were 0.79-2.0, 0.21–0.28, and 17.22–20.75 µmol L− 1, respectively. In a strategic part of Indian coast, this study enabled the location and determination of SGD and thereby provided valuable data for adopting proper methodology to mitigate the issue of groundwater scarcity and pollution.