Diagnóstico espacial-temporal da qualidade da água do Rio Iguaçuna região da Bacia do Alto Iguaçu

Abstract

The aim of this study was to observe the water quality of the Iguaçu River, Brazil, along its route, observing the pollution levels at locations of different degrees of urbanization where the river crosses, and also analyze the evolution of water quality over the years. Were selected for this the nine physicochemical parameters that compose the Water Quality Index (WQI) of the Environmental Company of the State of São Paulo (CETESB): pH, BOD, DO, Turbidity, CF, NT, FT and ST. It was also verified the attendance of the patterns of CONAMA Resolution No. 357/2005. .As the population density of the cities near the river has increased in recent years, the water quality has fallen significantly. The most urbanized parts, near the capital and metropolitan area, are the biggest contributors to the river’s degradation, mainly due domestic and industrial sewage which reaches the river without a proper treatment. In this region, water quality calculated by the method of WQI came to be classified as the worst index level - very bad quality. Other historical data from further parts, where the discharge of effluents tends to be lower, the water showed signs of recovery, coming to be classified as good. The river water is more degraded in passages where there are more polluted effluents. This is a strong indication that these have a direct influence on the river quality. The pollution levels of the river decreases when leaving the most densely inhabited areas, however, it was found that the Biochemical Oxygen Demand, Total Nitrogen, Fecal Coliforms, and especially the Total Phosphorus, even in the furthest points, often failed to achieve levels within the limits established by law, whereas the levels of Total Phosphorus were rarely found within acceptable ranges.