Avaliação integrada da qualidade da água do Rio Uberabinha - MG com base na caracterização química dos sedimentos e de espécimes da ictiofauna

Abstract

The physical, chemical and biological characteristics of water, which together allow the evaluation of its quality, remain associated with a series of processes that occur in the water body and its drainage basin. The consumption of water with quality specified in the legislation is of fundamental importance for health promotion and prevention of risks related to water contamination due to the adverse effects of human activities. For each preponderant use of water, there is a required quality, according to the standardization proposal by legislation. The standard of water quality and effluent is required based on laboratory analysis of essentially physicalchemical parameters. However, these parameters are generally insufficient, because it is impossible to determine all the chemical components in a water sample to evaluate its potential toxic effects on the biota. In evaluating the impact of certain substances on aquatic life it is necessary to use living organisms as bioindicators. Thus, this study aimed to promote an integrated evaluation of water quality of the Uberabinha River, in the City of Uberlândia - Minas Gerais - Brazil, which had not been done heretofore. The research was based on the chemical characterization of sediments, because they are substrates for a wide variety of organisms, which feed higher trophic levels and the use of fish as bioindicators of genotoxicity. Four samples were taken in different seasons of the year: rainy, dry, very dry, transition between rainy and dry. Five evaluation points were established, where the water samples and sediments were collected to be forwarded for review and any necessary procedures. In defining these five sampling sites, we sought to identify areas that characterize the natural flow of water upstream and downstream of the city, and the areas where human interferences are significant. For the water samples the following parameters were evaluated: temperature, pH, odor, color, turbidity, hardness, fluoride, phosphate, chloride, nitrate, nitrite, ammonia, sulfates, sulfides, chlorine residuals, surfactants, dissolved oxygen, dissolved solids, COD, BOD, barium, coliforms and fecal coliforms. The Water Quality Index was calculated and compared with the values set out in legislation. For the sediment samples the following parameters were evaluated: fixed solids, volatile solids, aluminum, cadmium, calcium, lead, copper, chromium, iron, manganese, potassium, sodium, zinc, organic matter, total carbon, as well as the pH, density and particle size analysis. Values obtained for the concentrations of cadmium, lead, copper, chromium and zinc were compared with the values of Sediment Quality Guidelines - SQVG, national and international. The results obtained with tests performed on specimens of micronucleus Catfish, Rhamdia quelen, demonstrated the effect of contamination at the sampling points. Multivariate statistical analysis was used in the treatment of data, to correlate various contaminants and not only the addition of the toxicity values of the different components analyzed individually.