Influência urbana na qualidade da água da bacia do rio uberaba: Uma avaliação ecotoxicológica

Abstract

Ecotoxicological tests applied to Tradescantia pallida, Allium cepa and Lactuca sativa were used to assess the quality of the Uberaba River basin under urban area influence. Water samples were collected at eight different points during the dry season. The samples were assessed using the following toxicity indicators: micronuclei percentage in T. pallida pollen grains (TRAD-MN), seed germination, root growth, mitotic index (MI) and micronuclei in A. cepa root-cells, and seed germination and root growth in L. sativa. Water physicochemical parameters such as temperature, dissolved oxygen (DO), pH and electric conductivity were assessed in situ. The three plant species were efficient bio-indicators, since they presented good cost-benefit and fast and easily interpreted results, thus completing the physicochemical parameters. There was strong correlation between seed germination and root growth among the ecotoxicological parameters assessed in L. sativa and A. cepa. The micronuclei percentage in T. pallida and the MI in A. cepa presented strong correlation with water electric conductivity and moderate and negative correlation with DO. Water electric conductivity ranged from 75 to 438 µS.cm-1; and the DO concentrations ranged from 0.5 to 6.9 mg.L-1. The importance of pollution control measures in the Uberaba River basin stands out. From the supply-water capture point, the basin is strongly affected by pollution, mainly in the tributaries that cross the city. It presents a short, or almost absent, riparian forest line, residues on the river banks, and it is impacted by discharges of untreated sewage, among other anthropic actions.