Monitoring of submarine groundwater discharge along the Donnalucata coast in the south-eastern Sicily using underwater gamma-ray spectrometry

A novel technique for monitoring of submarine groundwater discharge (SGD) in coastal zones based on an in situ underwater gamma-ray spectrometry of radon-decay products is described. Several sites were visited during the IAEA’2002 expedition offshore Donnalucata in the south-eastern Sicily. Continuous monitoring of 222Rn in the beach spring at Donnalucata has shown variable 222Rn activity concentrations in groundwater (from 12 to 19 kBq m - 3 ), depending inversely on water levels during tide. Spatial variations of SGD have been observed in the Donnalucata boat basin. Average 222Rn activity concentrations in seawater varied from ∼ 0.1 to 3.7 kBq m - 3 , showing an inverse relationship with salinity. A continuous monitoring carried out at the site closest to the coast has also revealed an inverse relationship of 222Rn activity concentration on tide and salinity. The 222Rn concentrations in seawater varied from 2.3 kBq m - 3 during high tides to 4.8 kBq m - 3 during low tides, confirming the tidal influence on SGD.