Avaliação da contaminação de corpos aquáticos da cidade de Parintins(AM) por esgoto domestico utilizando esteróis como marcadores moleculares

Abstract

Despite being the most preserved Brazilian biome, the Amazon encompasses the states of the Northern region of Brazil, which presente the worst rates of sewage collection and treatment. Similarly, environmental studies assessing levels of contamination of Amazonian water bodies are scarse, especially in regions far from the capitals. Therefore, this study aims to assess the contamination of aquatic bodies of Parintins (AM) by domestic sewage using sterols as molecular markers. For that, sixteen samples of surface sediments were collected in the following water bodies: Lagoa da Francesa, Lago Macurany, Lagoa Azul, Lago do Areal, Lago Parananema, and Lago do Aninga. Extraction of sedimentar organic matter was assisted by ultrasound, and the crude extract was fractionated to obtain a fraction rich in sterols, which was analyzes by liquid chromatography coupled to tandem mass spectrometry to determine cholesterol, epicoprostanol, coprostanol, cholestanol, brassicasterol, ergosterol, campesterol, β-sitosterol, stigmasterol, and sitostanol. The total sterol concentration ranged from 1,04 to 206,68 μg g-1, whereas coprostanol concentration ranged from 0,040 to 10,00 μg g-1 , revealing that some water bodies of Parintins present highlevels of contamination by domestic sewage. The absolute concentrations of the fecal marker were corroborated by the relative proportion and the diagnostic ratios. Therefore, this study revealed that the Lagoa da Francesa and the Lago Macurany channel that connects to Amazon River are the regions that most accumulate organic matter from untreated domestic sewage. In addition, it was found that the expansion of urban network towards Macurany, Parananema e Aninga lakes is compromising the quality of such aquatic bodies, although they are regions surrounded predominantly by vegetation. This pioneering study demonstratesthe need to expand investigations and monitoring of aquatic bodies of Parintins regarding composition and fluxes of organic matter. It also shows the need to require immediate public action, such as implementation of a sewage collection and treatment system, especially in the urban area.