Continuous monitoring of multiple submarine springs by means of gamma-ray spectrometry

The measurement of radiotracers is recognized as a major tool for the investigation and characterization of submarine groundwater discharges, while the use of underwater gamma-ray spectrometry has been proved a robust solution for the qualitative and quantitative determination of radionuclides in the aquatic environment. The capability of online continuous monitoring of submarine springs by means of gamma-ray spectrometry for direct estimation of SGD velocity and discharge is presented. The quantification of SGD flux rate is based on radon progenies time-series provided by two spectrometers placed above the seabed and near the water surface respectively, coupled with water level and meteorological data. The proposed methodology has been applied for a 5-month period in a coastal karstic system where multiple submarine springs occur at Anavalos-Kiveri, Greece. The estimated flux rates derived from the measured activities revealed significant SGD temporal variations with the mean discharge of 12 m3 s−1 being compatible with previous measurements. The advantages and limitations of direct SGD estimation via underwater gamma-ray monitoring are also discussed. •Online monitoring of multiple submarine springs via gamma-ray spectrometry.•Spontaneous application of KATERINA and GeoMAREA underwater detectors for 5 months.•Satisfactory agreement between manual and FSA based spectral analysis.•Activities of radon progenies reached up to 34 Bq l−1 while 40K was below MDA.•Daily SGD flux varied between 0.1 and 2.4 m s−1 with mean annual discharge of 0.2 km−3.