Efeito da pressão urbana sobre a qualidade da água em lagos da bacia do ribeirão Cambé – PR: análise físico-químicas, microbiológicas e bioensaios de fitotoxicidade

Abstract

Uncontrolled urban expansion has intensified pressures on water bodies, especially lakes in watersheds located in urbanized areas, where land use and occupation directly influence water quality. In this context, the present study aimed to evaluate the effects of urban pressure on water quality in lakes of the Ribeirão Cambé Watershed through physicochemical, microbiological analyses, and toxicity bioassays. The study area includes the main course of the Ribeirão Cambé basin (Point 1), upstream of the artificial lake formations created by dams, as well as Igapós IV and II Lakes (Points 2 and 3) and the lake of Arthur Thomas Park (Point 4), lakes with scenic and recreational significance for the municipality of Londrina. For greater integrity and reliability of the analyses, all sampling points were separated by banks, denoted as Right Banks (RB) and Left Banks (LB). The samples were collected in two seasonal campaigns, represented by the dry season (August) and the rainy season (November). The assessed physicochemical parameters included pH, temperature, total dissolved solids (TDS), dissolved oxygen (DO), electrical conductivity, and chemical oxygen demand (COD). Microbiological analyses examined the concentrations of Escherichia coli, total coliforms, and heterotrophic bacteria. Toxicity bioassays were conducted using seeds of Allium cepa (onion), Lactuca sativa (lettuce), and Cucumis sativus (cucumber), and only the tests with C. sativus showed lower sensitivity to the tested samples. The results revealed significant seasonal differences for each water body, highlighting primarily the decrease in DO levels and the significant increase in E. coli and total coliforms during the rainy season due to surface runoff and the input of organic matter. Lake Igapó II showed the greatest changes in its SD due to the identification of an illegal sewage connection, reflected in the increase of microbiological indicators and the subsequent occurrence of eutrophication. In general, the study highlighted the interference that urban pressure directly exerts on water quality, reinforcing the need for continuous monitoring, maintenance of sanitation structures, and preservation of the banks to mitigate the impacts.