Isotope techniques for assessment of submarine groundwater discharge and coastal dynamics in Ubatuba coastal areas, Brazil

The application of Rn-222 and the four naturally occurring Ra isotopes (using an one-dimensional advection-diffusion model) was shown as a tool to assist in the interpretation of coastal ocean circulation, groundwater input and biogeochemistry at Ubatuba region. Since they do not require steady-state conditions with respect to mixing, these isotopic techniques can supply useful data which coupled with salinity or any other tracer distributions, provide powerful constraints to follow the circulation patterns and calculate fluxes of several dissolved materials to the ocean. Obviously, additional work during different conditions shall be carried out to estimate average exchange times, fluxes and its seasonal variations. Once it was indicated and quantified in a previous research work, carried out in Ubatuba using Rn-222 as a tracer, that there is a significant inflow of subsurface fluids at rates in excess of several cm per day in the same embayments studied here, we intend to use the Ra data set and the residence times obtained to perform a mass balance (integrating river and groundwater end-member concentrations) to quantify the groundwater input for the same area. This is a research in progress.