Metal concentrations in marine sediments of the Rio de Janeiro Coast (Brazil): A proposal to establish new acceptable levels of contamination.

This work aims to propose new standards to assess the degree of sediment contamination in saline and brackish environments, since the legislation currently used in Brazil is based on Canadian/American regulations, which do not comply with the conditions in Brazil. This study is based on geochemical analyses of 340 surface sediment samples collected in the Green Coast region (Rio de Janeiro, Brazil), including Mangaratiba, Angra dos Reis and Ribeira coves and Ilha Grande and Sepetiba bays. This region is influenced by industrial, harbor, urban and tourist activities and was affected by a dam rupture episode that released contaminated material. The results show heterogeneity in the distribution and range of metal concentrations in the study area depending on the supply of metals from natural and anthropogenic sources. Environmental characteristics such as coastal and tidal currents, water temperature and salinity, local depth, sediment grain size, sedimentary dynamics and biogeochemical processes influence the dispersion or retention of metals. The pollution load index (PLI) suggests that Sepetiba Bay is the region with the most environmental degradation due to anthropogenic contamination. In this context, we propose the establishment of new levels of contamination according to the Cd, Cr, Cu, Mn, Ni, Pb, V and Zn concentrations in sediments of salt and brackish waters, considering I) background level; II) level 1 - with anthropogenic influence; and III) level 2 - contaminated. The results of this work also suggest that, except for zinc, the range of metal concentrations admitted by Brazilian legislation are quite permissive and not adequate for Brazilian coastal environments.