Bioavailability assessment of metals from a nickel mining residue in the gastrointestinal tract of Oreochromis niloticus in vivo.

Mining to obtain ferronickel by the pyrometallurgical process involves a calcination stage that generates a highly metallic solid dust. This study evaluated the bioavailability of metals from calcination dust after being ingested by Oreochromis niloticus. Chemical analysis was performed on the whole body and histological analysis was performed on the gills and gastrointestinal tract of fish to evaluate potential bioaccumulation. After 96 h of exposure to the dust, gill tissue contained a small amount of particulate matter, while the gastrointestinal tract was filled with the material, generating high values of metals in the fish whole body chemical analysis. However, after 15 and 30 days in clean water, both the gills and gastrointestinal tract were nearly devoid of particles and metal concentrations in the fish whole body had largely returned to baseline levels.

Evaluation of acute toxicity, cytotoxicity and genotoxicity of a nickel mining waste to Oreochromis niloticus.

The pyrometallurgical process of mining for obtaining ferronickel involves a stage of calcinations. At this stage a residue is generated described as a calcination dust of fine black grains. Analysis of this material revealed a significant presence of Fe, around 53,000 ppm and Ni, around 14,000, beyond of other metals as Al, Mn, and Cr. Adults and larvae of Oreochromis niloticus were used to evaluate acute toxicity, cytotoxicity and genotoxicity, and histopathological effects. The data obtained show absence of toxicity in concentrations of 5, 10 and 50% but a considerable potential for bioaccumulation in the fish's body.

Histopathological effects of [D-Leu(1)]Microcystin-LR variants on liver, skeletal muscle and intestinal tract of Hypophthalmichthys molitrix (Valenciennes, 1844).

This study evaluated the effects of [D-Leu(1)]Microcystin-LR variants, by the exposure of Hypophthalmichthys molitrix to Microcystis aeruginosa NPLJ4. Fish was placed in aquariums and exposed to 10(5) cells mL(-1). For 15 days, 05 individuals were removed every 05 days, and tissue samples of liver, skeletal muscle and intestinal tract were collected for histopathologic analyses. Following exposure, those surviving were placed in clean water for 15 days to evaluate their recovery. A control without toxins was maintained in the same conditions and exhibited normal histology and no tissue damage. In exposed fish, samples were characterized by serious damages that similarly affected the different organs, such as dissociation of cells, necrosis and haemorrhage. Samples showed signs of recovery but severe damages were still observed. The results should be valuable to analyze the potency of microcystin toxicity and to help in the diagnosis of fish deaths.