Qualidade da água do baixo curso do Rio Itapecuru e as implicações na saúde humana e usos múltiplos

Abstract

The Itapecuru River basin is used by millions of people, however, this region has been facing serious environmental problems, especially regarding the pollution of water resources. This condition endangers the health, safety and well-being of the population, as knowledge of water quality conditions is often absent. Thus, this work analyzed the condition of water quality of the low course of the Itapecuru river and the implications for human health and multiple uses, seeking to produce information that will guide the use of this resource, improve the environmental management of water resources and foster community awareness and environmental education. The study was conducted from field research carried out in the lower course of the Itapecuru River, concentrated in the territorial boundary of Itapecuru-Mirim municipality. It consisted of the analysis of land cover and use, the collection of water samples that were performed at 5 points spread over 17.6 km along the Itapecuru River, with the city of Itapecuru-Mirim as a reference, with a point in the center from the city, two upstream and two downstream, plus 5 streams, tributaries of the Itapecuru on the right bank, three of which are in the most urbanized area of the city and two in the semiurban area. The environmental variables measured were: hydrogen potential (pH), dissolved oxygen (OD), temperature, electrical conductivity, total solids, total suspended solids, total dissolved solids, turbidity, total phosphorus, phosphate, total nitrogen, total ammonia nitrogen, nitrite, nitrate, biochemical oxygen demand (BOD), total coliforms, thermotolerant coliforms and Escherichia Coli. The water quality index - IQA was used to determine the quality of water for public supply and the ICC compliance framework to define the uses that can be performed with adequate safety. As a statistical test, we performed the analysis of variance - ANOVA and the principal component analysis - PCA. The results showed that land use and land cover is distributed in classes in the following proportion, forested areas 45.75%, rural areas 32.91%, uncovered areas 9.58%, agricultural areas 7.24%, urbanized areas. 1.33%, mining areas 0.33% and water resources 0.28%. The water of the Itapecuru River and most of the studied streams presents the quality class of the IQA, regular. Having an acceptable quality for public supply after conventional treatment. It also showed that the water quality of the Itapecuru river in the analyzed section and of all streams is classified in the ICE poor class, having as reference the class 2 of the Conama Resolution 357/2005 freshwater and bad in the ICE class, quality of the ECI when analyzed on the basis of the freshwater class 3 criteria of that resolution. Defining that the current water quality condition of the studied water bodies is not in conformity with the quality class to which they are classified, class 2 and also to class 3. It is thus shown that all uses, which can only be carried out with the water quality condition in accordance with class 2 and 3, are sealed to the water bodies analyzed. This fact reinforces the importance of framing water bodies, monitoring, preparation and dissemination of water quality reports, to ensure users the development of possible uses with adequate safety.