A statistically valid agreement (95%) for copper and lead, and a recovery of 62% for chromium can be observed.
The aqua regia leaching provides a total recovery for many metals but not for chromium. Although the decision was made to proceed only with the two other cores, it was done an estimative of the actual sedimentation rate at this region applying the constant flux and constant sediment accumulation rate model (CF: CS) on the first 25 cm Although interventions in Guanabara Bay have occurred since colonial times, the major interventions have happened in the twentieth century with the industrial development of the regions surrounding the bay.
The sands are distributed at the entrance of the bay and the central channel extending to Governor Island.
The supply of river sediments is controlled by seasonal climatic cycles.Guanabara Bay is one of the most important coastal bays in Brazil and is an estuary of 91 rivers and canals surrounded by the cities of Rio de Janeiro, Duque de Caxias, São Gonçalo, Niterói and some other small towns and villages.its greatest extent in a straight line is 36 km between the end of Copacabana beach and the mouth of the Magé river.Heavy summer rains are responsible for the most significant inflows of sediment.The sea, often considered the main source of sediment for many environments, has been considered a secondary source for Guanabara Bay.In this direction, heavy metals were determined along the Three sediment cores were collected using divers at the sampling points shown in Figure 1.The sampling point coordinates and main characteristics are presented in Table 1.The limits of detection were several orders of magnitude lower than the elemental concentrations found in the sediment samples.Table 2 presents the results obtained for the determination of Cr, Cu and Pb on marine sediment sample IAEA-405 together with the reference values.(five times higher than the baseline values) were observed for both sediment cores, which agree with the reviewed existing data in the literature related to Guanabara Bay sedimentation rates based on Pb flux and on the historical record of the main physical interventions occurring in the last century, such as embankment, the channeling of main rivers and the construction of express roads.At the end of this process, only one sediment core dating could be adequately validated.