Abstract
The Potential Ecological Risk Index (PERI) was proposed by Håkan- son in 1980 to be used as a diagnostic tool for water pollution. The aim of this study was to apply the PERI for tropical conditions, proposing modifications. The metal contamination of 15 areas, including five bays, from the coastal systems of the Rio de Janeiro State, Brazil, which pre- sent different pollution degrees and trophic status, was assessed. For environment sensitivity assessment through bioproduction estimation, the ratio of total phosphorus (in mg/g)/organic matter in sediment (in %) ×100 was used, instead of the correlation between total nitrogen and organic matter as used in the original index calculation. The results for environment sensitivity were correlated with the concentration of acid volatile sulfides in sediments and with chlorophyll-a of the water column, showing a compatible relationship between water trophic status and se- diment anoxia. The highest degree of contamination (DC) was found for the N-NW sector of the Guanabara bay (60.21 – classified as very high), followed by the Sepetiba bay stations, which showed DC values classified as moderate. The Ilha Grande bay and Paraty (Mamanguá) showed low DC values. The station of the Guanabara bay was the only one classified by the index as of very high ecological risk (PERI=697), followed by three stations classified as of moderate risk (Mouth of Guanabara bay; Garsas, Sepetiba bay; and Angra, Ribeira bay). All the other stations present low risk associated with metal exposure. As mercury is the metal of highest toxicity factor in the Håkanson formulation, a control test was applied to observe the relationship between PERI and mercury concentrations in fish and its bioconcentration factors, which are related to mercury bioavailability in the system. The results of the modified PERI were fully satisfactory for ranking areas of contamination. Keywords: coastal systems, toxic metals, trophic status, sediments, fish.
Highlights
For an ecological risk assessment associated with pollutant exposure in aquatic ecosystems, several environmental factors must be considered, such as chemical, physicochemical, biological, and ecotoxicological parameters
This study aimed to investigate the possibility of adaptation of Potential Ecological Risk Index (PERI), a good idea as indicator, to an estuarine/ marine ecosystem with high dynamics, including superficial sediment resuspension, at tropical climate, testing the sensitivity of the index to classify five bays with different contamination degrees and trophic state of water column
The study was made at five bays from the coastal system of the Rio de Janeiro State (Brazil), with different degradation degrees (Figure 1): Guanabara bay – largely polluted; Sepetiba bay – has some contaminated areas; Ribeira bay – at initial state of degradation with punctual anthropogenic alterations; Ilha Grande bay – with intense tourism activity, with well-preserved areas; and Paraty – Mamanguá small cove, which preserves the properties of natural ecosystems
Summary
For an ecological risk assessment associated with pollutant exposure in aquatic ecosystems, several environmental factors must be considered, such as chemical, physicochemical, biological, and ecotoxicological parameters. Abreu (2009) applied this index for some sectors of the Guanabara bay (State of Rio de Janeiro, Brazil), showing that the highest risks to biota were found in northwest and west sectors, especially at the area of Rio de Janeiro port Another index is the Potential Ecological Risk Index (PERI), proposed by Hakanson (1980), to be used as a quick and practical tool for environmental assessment, obtaining as results the pollution classification of areas and the identification of the toxic substances of interest, supporting actions for pollution control of limnic aquatic systems. The results have been tested on 15 Swedish lakes representing a wide range in terms of size, pollution, physicochemical characteristics (especially, pH), and trophic status This model, despite being formulated in 1980s and for limnic systems, has an organized structure based on simple algorithms, including the most important environmental parameters for an ecological risk assessment, and includes the mathematical relationships between them
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