Geochemical fractionation of metals and semimetals in surface sediments from tropical impacted estuary (Guanabara Bay, Brazil)

• DOI: 10.1007/s12665-015-4127-y
• Publication Date: 2015-02-18T07:22:19Z
• Authors: R. C. Cordeiro; W. Machado; R. E. Santelli; A. G. Figueiredo; J. C. S. Seoane; E. P. Oliveira; A. S. Freire; E. D. Bidone; F. F. Monteiro; F. T. Silva; M. F. G. Meniconi
• Keywords: Biogeochemical Cycle

A three-step sequential extraction procedure, which was based on the BCR method, was used to analyse Guanabara Bay sediment samples to evaluate the potential mobility of some metals and metalloids. Zn and Cd were found to be the most labile metals because these were recovered in the first extraction stage and were associated with the non-residual fraction of the sediment. In contrast, Cr, Cu, Ni, and Hg were the least labile metals, and 62 to 84 % of the concentrations of these metals were found in the organic residual fraction of the sediment samples. The spatial distribution of the metal concentrations in Guanabara Bay led to the identification of various sources of contamination. The continental sources, which were related to Fe and Al, were distributed in the northern and central sectors, although lower concentrations were found in the mouths of the rivers that flow into the estuarine system of Guanabara Bay. The urban emission sources are related to the discharges of the Sao Joao de Meriti River, which exhibit significant levels of Ba, Cd, Ni, Zn, and Hg. The Sao Joao de Meriti River and harbour activities also show a predominance of Pb and Cu. The system formed by the Iguacu River and the Sarapui River is mainly characterised by V and Cr. The metals associated with biogeochemical processes, such as As and Mn, were found in the central sector of Guanabara Bay.