Risco de contaminação ambiental em área de mineração de cobre e estudo toxicológico em Drosophila melanogaster

Abstract

Mining activities are widely known to generate severe environmental impacts, with heavy metals being one of the main and most toxic wastes of this type of activity. The toxic potential of heavy metals to animals and plants is diverse and can lead to dead bodies. The molecular pathways by which toxic metals cause their effects are still not fully understood. In this way, this work evaluated the concentrations of Copper (Cu) metal in an environmental reject area of mining activity and its effects in several toxicological parameters using as experimental model the species of fruit fly Drosophila melanogaster. For this, water samples were collected from an open pit and the copper content was quantified by X-ray fluorescence spectrometry (FR-X) and by colorimetric analysis using the cuprizone complexation technique. In addition, the flies were exposed to different concentrations of copper sulphate: 0.5 mM, 1.0 mM, 2.5 mM, 5.0 mM and 10.0 mM and 100.0 mM, through the culture medium . Mortality was determined over a period of seven days. The behavioral effect caused by exposure to 1.0 mM, 2.5 mM, 5.0 mM copper was assessed by the climbing test. In addition, these same concentrations were used to evaluate the activity of the enzyme acetylcholinesterase (AChE) and levels of free thiols (SH) according to Ellman's method. Already the production of reactive oxygen species (ROS) was evaluated by spectrofluorimetry using the oxidation method of dichlorofluorocine diacetate. The quantification of copper in the fly's organism was determined by the FR-X method. As a result, the average copper concentration in water is 0.51 mg / L. Mortality indicated that concentrations of 0.5 mM 1.0 mM and 2.5 mM had no significant influence on the survival analysis, whereas the concentrations of 5.0 mM, 10.0 mM and 100.0 mM showed a decrease statistically significant in the survival of individuals. The behavioral analysis showed a decrease in locomotor activity, significant only in the 5.0 mM group. Copper at concentrations of 0 mM and 1.0 mM did not cause alteration in AChE enzyme activity and at 2.5 mM and 5.0 mM concentrations there was a tendency for decreased enzyme activity. Testing the free SH groups demonstrates a decrease in SH concentrations at the concentration of 5.0 mM. In the analysis of ROS, the results showed a tendency to decrease fluorescence, but the data were not statistically significant. With the analysis of the flies in the FR-X, it was possible to identify that the copper was bioaccumulated in the body of the individuals. Thus, it is concluded that the copper metal at the concentrations tested shows significant toxicity in Drosophila melanogaster, but only at high concentrations. However, at lower concentrations such as those found in the tailings area, Cu does not appear to have a toxic effect in this experimental model. In addition, the concentrations of copper 0.51 mg/L found in the tailings area exceed the limits for this metal in current legislation, indicating that this is an area of environmental contamination.