Water quality and definition of preponderant parameters for monitoring in the Puraquequara River, Manaus, Amazonas, Brazil

Abstract

The landscape of the Puraquequara River watershed, before built by forests, became an area of exposed soil, houses, places, shipyards, floating restaurants, industries, among others. All these users use water resources, and the qualities with which they are developed are of public interest. In this sense, the objective of this research was to analyze physical, chemical and biological parameters in the Puraquequara River and to identify the preponderant ones for monitoring, through principal components and factorial analysis, also aiming to contribute to the management of water resources. Four collection and analysis campaigns were carried out at six points along the lower course of the Puraquequara River between 2021 and 2022. The waters presented values ​​of dissolved oxygen oscillating between 1.26 mg.L^-1 and 6.26 mg.L^-1 and high values ​​of Biochemical Oxygen Demand (BOD) in the flood (up to 20.1 mg.L^-1). These are acidic waters (pH<6), with a temperature variation between 79,80 °F and 88,34°F. In the ebb, the smaller volume of water results in the increase of particles, influencing the turbidity and the total solids. The higher conductivity during the rainy season results from the leaching of material from the banks into the hydrous body. The total phosphorus was not in compliance with the environmental legislation in some points, and, together with the total nitrogen, the thermotolerant coliforms and other parameters, portray the anthropic influence in the alteration of these. Turbidity, dissolved oxygen, thermotolerant coliforms, BOD and total solids explained the greatest variability in the data and are the most representative in terms of water quality. Therefore, it is recommended to strengthen management instruments to maintain or improve water quality and continue to serve multiple uses.