Trophic index and recreational water quality at beaches on the lower Tapajós River, Amazonia, Brazil

Abstract

The degradation of environmental quality, mainly caused by anthropic factors, has an immediate impact on watercourses. This way, monitoring water resources is of fundamental importance for maintaining water quality and human well-being. In this context, this work aimed to investigate the spatio-temporal conditions of the water quality of the beaches on the right bank of the lower Tapajós River, regarding the Water Quality Index (WQI) and the Trophic State Index (TSI), in the municipality of Santarém/Pará. For this, the following beaches were sampled along the right river bank of the Tapajós River: Muretá, Cajueiro, Ponta de Pedras, Pajuçara and Maracanã, and field and laboratory analyzes were carried out of the sets of fundamental parameters that make up the WQI and TSI indexes. Four monitoring campaigns were carried out in two phases of the river hydrograph: low water season (December 2015 and January 2017) and high water season (May 2016 and May 2018). The results showed WQI ranging from 67 ± 5.8 on Maracanã beach in the low water season to 77 ± 3.8 for Muretá beach in the high water season and TSI with minimum variation (40 ± 7.5) and maximum (48 ± 6.8) recorded coincidentally on Pajuçara beach in the low water and high water season, respectively. These results demonstrated that the evaluated indices, WQI and TSI, indicate that the investigated beaches have good quality and low potential for eutrophication.

Keywords: Environmental Quality, Eutrophication, Tapajós River.