English

Abstract

Coal mining produces amounts of residues containing high levels of chemical elements that contaminate surface and ground water. In the last several decades, constructed wetlands systems have been used to improve the quality of coal mine drainage. Although the impact of coal mining-related toxic substances on fauna community is an important conservation concern, it has not been studied intensively. The objective of this study was to evaluate the possibility of use a microcrustacean (Artemia sp.) and pearl cichlid (Geophagus brasiliensis Quoy & Gaimard, 1824) to assess the toxicity and the genotoxicity, in a constructed wetland at biopolishing acid mine drainage (AMD) previously treated by conventional physical and chemical processes. Effluent samples were collected at four stations along the treatment system: 1 - pH control and precipitation, 2 - second damping pond output, 3 - wetland input and, 4 - wetland output. Acute toxicity analysis using Artemia sp. was performed at AMD concentrations of 0% 25%, 50%, 80%, 90% (diluted with mineral water) and 100% (not diluted). Genotoxicity analysis was performed using the comet assay on peripheral blood and hepatic cells of G. Brasiliensis. The Artemia sp. test results indicated lethality of 30% at station1 and 0% at station 4 at 100% AMD concentration, indicating that the constructed wetland is effective at reducing the toxicity for this organism. The comet assay indicated that the effluent is genotoxic, with an increase in the DNA damage index from station 1 to 3 and a significant reduction at station 4, in both blood, and hepatic cells. This increase could be due to the presence of oxidated reactive species that are in between station 3 and 4 partially captivated by the living forms present in the wetland, reducing the genotoxic potential of the effluent. The results suggest that the treatment is efficient at removing toxicity and reducing genotoxicity but further improvements are required.