228Ra and 226Ra in coastal seawater samples from the Ubatuba region: Brazilian southeastern coastal region

Abstract

O presente trabalho apresenta os resultados de 226 Ra e 228 Ra obtidos durante o 4 o experimento de intercomparação referente à descarga submarina de água subterrânea (Submarine Groundwater Discharge, SGD) realizado em Ubatuba (SP), em novembro/2003. Este experimento visava testar, em um sistema de rochas cristalinas fraturadas, as diferentes metodologias existentes de determinação da SDG. Embora com objetivo distinto, decidiu-se participar deste experimento de modo a verificar se os isótopos de rádio poderiam ser empregados no estudo de mistura de águas na região e, também, testar a capacidade analítica do laboratório, visando uma futura validação de modelos de dispersão marinha para o local de instalação dos reatores nucleares de Angra dos Reis, distantes apenas setenta quilômetros da região do experimento. Além das concentrações de 228 Ra e 226 Ra, resultados de salinidade, bário e sílica também são apresentados e suas relações com a concentração de 228 Ra são discutidas. The present work reports 228 Ra and 226 Ra results obtained during the 4 th Submarine Groundwater Discharge (SGD) intercomparison experiment realized in Ubatuba, November 2003, aiming to test the methodologies on a fractured crystalline rocks system. Although with distinct objectives, it was decided to participate in this experiment in order to verify if radium isotopes could be used to determine water mixing rates in this region and to test the laboratory capability to perform, later on, a marine dispersion model validation at Angra dos Reis reactor site, located nearby. The results show that the SGD model constrains seems to be valid, at least for a distance of 20 km offshore, that corresponds to the distance between the reactor site and Ilha Grande, a 193-km 2 island existing at this site and probably an additional SGD source. Salinity, barium and silica results are also reported and their relation to 228 Ra concentrations is discussed.

Use of multitracers for the study of water mixing in the Paraíba do Sul River estuary

“…This is in contrast to the values observed by Moore and Shaw (2008) for several US estuaries. On the other hand, the values obtained in the present work are similar to those found in the region of Ubatuba and Ilha Grande Bay (Godoy et al, 2006;Burnett et al, 2008;Moore and Oliveira, 2008). Fig.…”

Using radium isotopes to characterize water ages and coastal mixing rates: A sensitivity analysis

“…We did not include any ARs involving 226 Ra because the activity of this isotope can be significant in offshore waters (Moore 2000b;Godoy et al 2006; and would thus affect the AR gradient. Additionally, ARs including 226 Ra are not often used in water age calculations.…”

Major Ion Chemistry in a Freshwater Coastal Lagoon from Southern Brazil (Mangueira Lagoon): Influence of Groundwater Inputs

“…However, little is known about the contribution of diffuse sources, such as groundwater discharge, because it is extremely difficult to quantify seepage rates and to separate the diffuse groundwater inputs from other processes. A few recent investigations addressed the input of groundwater into the coastal ocean from Brazil Godoy et al 2006;Oliveira et al 2006;Windom et al 2006), but no previous investigations have quantified dissolved species' inputs via groundwater into Brazil's coastal lagoons. They are usually shallow water bodies, oriented shore parallel, separated from the ocean by a sandy barrier, hypo-or hypersaline, and highly productive.…”