The physical-chemical characteristics of surface waters in the management of quality in clearwater rivers in the Brazilian Amazon

Abstract

Abstract The study of water quality in the Amazon region is important for understanding the functioning of ecological mechanisms. The standard that governs water quality in Brazil, including the Amazon, is Resolution CONAMA 357/05, which uses criteria inspired by standards from other countries. However, this resolution does not consider characteristics of Amazonian aquatic ecosystems, and this can lead to incorrect interpretation of the data. Furthermore, there are few studies on the physical-chemical characteristics of clearwater rivers in the Amazon and the influence of the forest-water interface. Therefore, water samples were collected from four clearwater tributary watersheds of the Amazonas and Tapajós Rivers during the dry season in the city of Santarém, Pará. Most of the points were collected in pristine areas in order to capture the natural physicochemical characteristics of clearwater rivers, as well as to show the importance of ecoregional aspects in water quality management. All samples were below pH 6.0, which represents non-compliance with the CONAMA resolution. Statistical tests yielded negative correlations between pH and conductivity (r = −0.87, p < 0.05), Therefore, the rivers of lower ionic load are influenced by the type of surrounding vegetation, which are characteristics that have been widely reported for blackwater rivers.