Calidad de agua del Arroyo Guazú del Departamento Central evaluada mediante indicadores biológicos, parámetros fisicoquímicos y ecotoxicológicos

Abstract

The waters of urban streams in the Metropolitan Area of Greater Asuncion are under great pressure from anthropogenic pollution of urban and industrial origin. The Guazu Stream is a watercourse that crosses the cities of Nemby and San Antonio and is affected by pollution throughout its course. The quality of its water based on its physicochemical, biological and ecotoxicological characteristics was used in this study to compare it with current national legislation. Water samples were collected at five different points in the months of July and November 2017. The results of the physicochemical parameters indicate that its waters possess class II and class III characteristics as established by the Ministry of Environment and Sustainable Development of Paraguay. Some parameters such as nitrate, total nitrogen, total phosphorus, dissolved oxygen, BOD5 and fecal coliforms presented values outside the allowed limits. The Water Quality Index gave Fair and Poor ratings, preferably towards the lower basin in the area where it flows into the Paraguay River, while the trophic status index categorized the stream as mesotrophic to hypereutrophic. There was a decrease in zooplankton diversity towards the mouth of the river. Therefore, the results indicated an increase in aquatic pollution. Ecotoxicological tests on Daphnia magna and Lactuca sativa did not detect the presence of toxic pollutants in the waters of the Guazu Stream.