Avaliação da qualidade da água dos lagos Igapó e do ribeirão Cambé (Londrina-PR) por meio do índice de qualidade da água (IQA)

Abstract

This study aimed to assess the water quality of the four Igapó Lakes and the Ribeirão Cambé basin, located in Londrina, Paraná, Brazil, through the monitoring of physicochemical and biological parameters and the application of the Water Quality Index (WQI). Sampling campaigns were conducted between May and September 2025, with sampling at 10 points distributed throughout the four Igapó Lakes, covering both dry and rainy periods. Laboratory analyses followed methodologies standardized by CETESB and the Standard Methods, including dissolved oxygen, thermotolerant coliforms, pH, BOD, temperature, turbidity, total solids, total phosphorus, and total nitrogen. The results demonstrated that the aquatic system is under intense environmental stress, predominantly due to anthropogenic impacts associated with illegal sewage connections, irregular discharge of effluents, and diffuse pollution from surface runoff. Although the WQI indicated a predominance of “Fair” and “Good” classifications, severe issues were observed when parameters were analyzed individually, particularly the supersaturation of dissolved oxygen and elevated pH values resulting from intense photosynthetic activity of algae and cyanobacteria. Comparisons with the CONAMA Resolution No. 357/2005 revealed numerous exceedances of water quality standards, especially for BOD, total phosphorus, pH, and thermotolerant coliforms. Sampling point 8 stood out as the most critical area, classified as “Poor” in both September campaigns, reflecting advanced eutrophication and a continuous input of organic loads at the lake’s outlet. The findings indicate that the Igapó Lakes system is significantly environmentally compromised, requiring measures such as stricter sanitation enforcement, macrophyte management, improved urban drainage, and the maintenance of a continuous monitoring program to promote water quality recovery and mitigate identified impacts.