Seasonal variations of 222Rn and SGD fluxes to Ubatuba embayments, São Paulo

Summary We describe here an application of excess ²²²Rn to estimate submarine groundwater discharge in a series of small embayments of Ubatuba, S?o Paulo State, Brazil. Excess ²²²Rn inventories obtained in 11 vertical profiles varied from (3.3±1.1) ^. 10³ to (19±5) ^. 10³ dpm ^. m^-2. The estimated total fluxes required to support the inventories varied from (0.6±0.2) ^. 10³ to (3.4±0.9) ^. 10³ dpm ^. m^{-2 .} d^-1. Considering these results, the submarine groundwater discharge advective rates necessary to balance the sub-pycnocline fluxes calculated in Ubatuba embayments ranged from 0.06 to 1.9 cm ^. d^-1. During the period of this investigation (from March/03 to May/2004), the highest ²²²Rn in excess inventories were observed late in the summer season (March). Taking into account all vertical profiles established, the relative variability was 67%. Although, if we consider only the fluxes determined in both Flamengo and Fortaleza embayments, the relative variation was 21%.