Abstract
The accelerated urbanisation without a planning, brought several environmental problems to Rio de Janeiro coastal zone, especially in areas such as Rodrigo de Freitas lagoon, which receives a great amount of untreated sewage every day. To assess the nature, potentially sources and extent of heavy metal pollution in the lagoon, sediments from the surrounding streets, from the entrance of the main canal that drains to the lagoon and from the bottom of the lagoon were collected and analysed by a modified selective extraction procedure in order to study the geochemical partitioning and bioavailability of Zn, Cu, Cr, Ni and Pb in these three compartments. The present study verified an increase in the Cu, Pb and Zn concentrations in the north of the Rodrigo de Freitas lagoon. Despite the different levels of oxidation between the sediments accumulated in the streets and in the bottom of the lagoon, the geochemical partitioning of the heavy metals did not show any pattern of variation for the metals, except for the element Cu. No concentrations were found in the soluble phase of samples collected in the surfacial sediments of the lagoon, suggesting no bioavailability of heavy metals.
Highlights
Originated primarily in the continental crust, soil, sediments and urban dust constitute effective deposits of pollutants
The aim of this work is to evaluate the levels of pollution in the Rodrigo de Freitas lagoon, and to access the mains sources of its pollutants, throughout the analysis of the total concentrations and the partition of the heavy metals in order to understand the geochemical dynamics of heavy metals in several compartments of this ecosystem
The third approach aimed at the collection of the samples in the urban runoff sediments in the streets around the lagoon, where 7 samples were collected, and in the mouth of the main canals that drains to the lagoon, where 8 samples were collected (Fig. 1)
Summary
Originated primarily in the continental crust, soil, sediments and urban dust constitute effective deposits of pollutants. In terms of toxicity and risk for the public health, heavy metals are frequently cited in studies dealing with deposited sediments in avenues of automotive transport (Olivero and Solano 1998). Heavy metals such as copper, lead and zinc are of particular interest in the studies on urban discharges due to their toxic character for the aquatic organisms and persistence in the environment (Hoffman et al 1984, Borchardt and Sperling 1997, Walker et al 1999, Brown and Peake 2006)
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