High concentrations of metals in the waters from Araguari River lower section (Amazon biome): Relationship with land use and cover, ecotoxicological effects and risks to aquatic biota

Abstract

The Araguari River is one of the most important water body in the Brazilian state of Amapá. However, the quality of its waters has been deteriorating and, recently, high concentrations of metals were found in water samples collected from its lower section. Overall, we aimed to evaluate land use and cover around three sampling sites located in the Araguari River lower section and its contribution to water pollution by metals; correlate land use pattern with detected metal concentrations; assess acute toxicity using the Daphnia similis test and genotoxicity using the Danio rerio bioassay of water samples from the three sampling sites; and investigate the risks arising from metals present in waters to aquatic biota. Riparian forest around all sampling sites is fragmented owing to the expansion of pasture areas, which showed a significant positive correlation (p < 0.05) with the concentrations of Hg and Cu in water samples. Water samples from sampling sites 2 and 3 presented acute toxicity for D. similis, and the D. rerio bioassay confirmed the presence of genotoxic pollutants in the waters from all sampling sites. Our preliminary risk assessment showed that individual concentrations and the mixture of metals posed a high risk to aquatic biota. Taken together, our results demonstrate that the conversion of native forest to pastureland contributes to water contamination by metals, which contributes to the risks to aquatic biota.