Potentially bioavailable metals in sediment from a tropical polymictic environment—Rio Grande Reservoir, Brazil

Abstract

Background, aim and scope Although many recent studies have focused on sediment potential toxicity, few of them were performed in tropical shallow aquatic environments. Those places can suffer short-time variations, especially due to water column circulations generated by changes in temperature and wind. Rio Grande reservoir is such an example; aside from that, it suffers various anthropogenic impacts, despite its multiple uses. Materials and methods This work presents the first screening step for understanding sediment quality from Rio Grande reservoir by comparing metal content using three different sediment quality guidelines. We also aimed at verifying any possible spatial heterogeneity. Results and discussion We found spatial heterogeneity varying according to the specific metal. Results showed a tendency for metals to remain as insoluble as metal sulfide (potentially not bioavailable), since sulfide was in excess and sediment physical-chemical characteristics contribute to sulfide maintenance (low redox potential, neutral pH, low dissolved oxygen, and high organic matter content). On the other hand, metal concentrations were much higher than suggested by Canadian guidelines and regional background values, especially Cu, which raises the risk of metal remobilization in cases of water circulation. Further study steps include the temporal evaluation of AVS/SEM, a battery of bioassays and the characterization of organic compounds.Sediments are an important phase in controlling metal toxicity to organisms, since they can act as both a source and a sink for such contaminants (Chapman et al. 1998). Physical and chemical parameters of sediments affect metal speciation and, hence, metal bioavailability and toxicity to organisms. Although many studies have been dedicated for the understanding of sediment dynamics and processes controlling the bioavailability of metals, few of them were performed in tropical shallow aquatic environments. In such places, minor changes in temperature and wind can have an enormous influence on water circulation over a 24-h basis, meaning that the water column changes from being stratified to non-stratified. Besides, high temperatures accelerate the metabolism of the whole system, including production/consumption of organic matter and equilibrium of chemical reactions.Water bodies located near urban areas are subjected to multiple stresses, among which metal contamination is of great importance, since metals are not degradable and can be biomagnified along the food web. Furthermore, the sources of metals are variable (atmospheric deposition, run off from ore exploration, input from industrial, and urban sewage). In this context, Rio Grande reservoir fulfills the characteristics for a good case of study. It is part of the Billings Complex, the greatest body of accumulated water in the São Paulo Metropolitan Region (São Paulo State, Brazil); it is polymictic, of multiple uses and suffers greatly from a variety of anthropogenic impacts.

Nitrogen and phosphorus in cascade multi-system tropical reservoirs: water and sediment

“…It was found that reservoirs with the greatest anthropogenic activities in the watersheds presented greater anthropogenic contributions of metals, as well as higher trophic levels. In the present study, some of the individual reservoirs showed a gradient from the upper portion to the dam, as observed by Mariani and Pompêo (2008) and Pompêo et al (2013) for metals in the sediments of the Rio Grande and Guarapiranga reservoirs (Brazil). Similar patterns for concentrations of N and P in sediment were observed in the five cascade reservoirs in the River Lozoya (central Spain), with spatial heterogeneity both among and within reservoirs (Lopez et al 2009).…”

“…All of these factors lead to a worrying scenario, as already observed, for instance, in the basins of the Billings and Guarapiranga reservoirs, also located in the MRSP. For decades, both drainage basins of those reservoirs have experienced substantial impacts that are reflected in the water and sediment quality, particularly due to eutrophication (Mariani and Pompêo 2008;Moschini-Carlos et al 2009Pompêo et al 2013;Cardoso-Silva et al 2014;Nishimura et al 2014;Pompêo, Kawamura et al 2015). Table 1 presents the hydrological information and characteristics of the CS reservoirs, according to ANA- DAEE (2013).…”

“…The most common effect is eutrophication, which is a consequence of high nitrogen and phosphorus concentrations and can cause additional contamination. For example, eutrophication can lead to the growth of harmful algae, whose control requires the application of hydrogen peroxide or copper sulfate, which can result in contamination of the sediment by copper (Caleffi 2000;CETESB 2008;Mariani and Pompêo 2008;Pompêo et al 2013). Causal relationships have been suggested between high levels of nutrients and the presence of other pollutants in superficial waters and sediments.…”

Ecological risk index for aquatic pollution control: a case study of coastal water bodies from the Rio de Janeiro State, southeastern Brazi

“…Nessa tabela pode ser observada a elevada concentração de cobre no sedimento do braço Rio Grande na represa Billings (Mariani & Pompêo 2008), que há décadas também recebe aplicações de sulfato de cobre para o controle do crescimento algal.…”

Sulfetos volatilizáveis por acidificação e metais extraídos simultaneamente na avaliação de sedimentos de água doce

“…15 Na Tabela 1 podem ser vistos valores típicos de SVA e MES em sedimentos aquáticos brasileiros. 61,[93][94][95][96][97][98] Na Tabela 2 são apresentados valores típicos de SVA e MES encontrados em diferentes partes do mundo, em locais sob as mais diversas influências antrópicas. 14,57,66,[99][100][101] Com relação ainda à mineralogia, Morse e Rickard 46 afirmam que a dinâmica química dos SVA é de difícil entendimento, já que sua constituição pode ser bastante variada.…”