Radium isotope (223Ra, 224Ra, 226Ra and 228Ra) distribution near Brazil's largest port, Paranagua Bay, Brazil

This work investigates the Ra-223, Ra-224, Ra-226 and Ra-228 isotope distribution in river, estuarine waters and sediments of the Paranagua Estuarine Complex (PEC). The stratification of the Ra isotopes along water columns indicate differing natural sources. In sediments, the radium isotope activities was inversely proportional to the particle size. The highest concentrations of Ra-223, Ra-224, Ra-226 and Ra-228 in the water column were found in the bottom more saline waters and towards the inner of the estuary. These relatively high concentrations towards the bottom of the estuary may be attributed to the influence of tidally driven groundwater source and desorption from particles at the maximum turbidity zone. The apparent river water ages from the radium isotope ratios, Ra-223/Ra-224 and Ra-223/Ra-228, indicate that the principal rivers that flow into the estuary have residence times from between 6 and 11 days. (C) 2016 Elsevier Ltd. All rights reserved.