Avaliação do potencial citotóxico e genotóxico do Rio Alegria, Medianeira – PR utilizando bioensaios com Allium cepa

Abstract

Water is considered a renewable resource that flows between compartments, marine and continental, forming the hydrological cycle. It is in the continent that water has its lowest volume, being fundamental for the maintenance of life and for economic development. Even só, water is continually polluted and, at the same time, its quality and reuse recovery mechanisms are being created for human benefit. This work aimed to evaluate the cytotoxic and genotoxic potential of Rio Alegria located in the municipality of Medianeira-PR using bioassays with Allium cepa. During the bioassays, water samples were collected from four different collection points distributed from the source to the mouth of the source. For the collection, four points of the Alegria River were denominated from P1 to the source, P2 to the capture dam, P3 to the point located in Alegria village and P4 to the mouth of the Ocoy River. The samples were then collected following the standards of ABNT NBR 9898 and then the physicochemical analyzes were done sequencing the use of the plant species Allium cepa popularly known as onion for the bioassays and preparation of the slides where the mitotic index was observed for evaluation of the number of cells in division. The results indicated normal and regular growth of the bioindicator (onion) roots when compared to a positive and negative control. It was observed that there was no necrosis or malformation in the roots of the Allium cepa for the sampled points of the river, and there was no macroscopic evidence of toxicity. The analysis of variance did not infer statistically significant differences at the 95% level for the mass gain. However, for the samples of points 3 and 4 the same test indicated differences in relation to the control for the length of the roots, suggesting effects on the development of the target species. Genotoxicity was assessed qualitatively by observing possible nuclear alterations. With cultivation in a solution of 0,0006 mg mL- 1 copper sulphate called the positively toxic positive control for the onion, it presented anomalies of binucleate cells and anaphasic bridges. The studies and analyzes carried out with the bioindicator Allium cepa showed the importance of monitoring the environmental quality, especially of the Alegria River, indicating that the changes due to the environmental impacts along its course exert an increase in the physical and chemical parameters, as observed in the characterization of the samples used in the tests and in the observed mitotic index increase effect. However, as observed in the toxicity tests using the onion as bioindicator such changes in the water concentration of the Alegria river possibly do not cause damage to the cytotoxic and genotoxic level because no chromosomal abnormalities occur in the samples tested. With the study of the bioindicators, it was observed that their use is extremely important because it is possible to verify the quality of the environment, thus indicating its level of change in its original characteristics, the use of the onion as a bioindicator if given as it is easy to cultivate, low price, the number of chromosomes to be easy to observe, high number of dividing cells and leaves an opening só that more tests can be performed possibly using other organisms bioindicators.