Avaliação da qualidade da água do Rio Lajeado Ipiranga através de testes toxicológicos e índice de qualidade da água

Abstract

Water is an indispensable element in the maintenance of all life forms, well-being and socioeconomic development, and may present different characteristics, depending on the location and conditions of the environment. With population growth and technological development, industrial and agricultural activities have intensified, resulting in a considerable increase in the levels of contamination in the environment, especially in water. Thus, the present study aimed to evaluate the water quality of the Lajeado Ipiranga river through the water quality index and toxicological tests with the microcrustacean Daphnia magna. The Lajeado Ipiranga river is the main source of supply in the city of Campinas do Sul-RS. It is located in the rural area of the municipality and was monitored in three localities: near a source (P1), where it is made the water catchment by the water supply company (P2) and a point further downstream located after the junction to the river of a stream that runs through the urban area of the municipality (P3), points delimited to cover a large part of its course d 'water. Six samples were collected, divided into two sample periods, the first period being carried out in november 2016, january and february 2017 and the second period in november 2017, january and february 2018. The water quality index (WQI) and toxicological tests were used to evaluate river water quality. The WQI was estimated by evaluating the following parameters: fecal coliforms, biochemical oxygen demand (BOD5,20), pH, temperature, dissolved oxygen, turbidity, nitrate, nitrite, ammoniacal nitrogen, total phosphorus and total solids. As for toxicological tests, acute tests were performed for all samples collected in the first period of analysis and chronic tests only for the samples collected in P3 of the first period of analysis, where both presented no toxicity. All the analyzed points presented classification as being of good quality, using as reference the IQA of CETESB-SP. However, when the IQA FEAM-MG was used as reference, the great majority of the points were classified as being of medium quality. In spite of the good quality registered in IQA of CETESB-SP, when each parameter was evaluated individually, some were found to be in disagreement with the limits established by CONAMA Resolution No. 357/2005, which are: Thermotolerant Coliforms, BOD5,20, Nitrate and Total Phosphorus. Considering the results of the parameters analyzed in this study, the results obtained are considered of concern and a continuous monitoring of this environment is necessary.