Spatial and temporal distribution of potentially toxic elements in the urban area of São Raimundo Basin in Manaus, Brazil

Contamination of surface water by metallic elements is an environmental concern in cities with industrial parks such as Manaus in Amazonas, Brazil. The concerns are related to the bioaccumulation of these elements and their toxicity, which affect the ecology of aquatic environments and human health. The study evaluated the role of seasonality in the concentrations of potentially toxic metals in the São Raimundo Basin in Manaus. Collections were carried out in June 2021, October 2021 and January 2022 at thirty collection points. The physicochemical parameters were analyzed according to the Methods for the Examination of Water and Wastewater of the APHA/AWWA. The metals were analyzed using optical emission spectrometry with inductively coupled plasma (ICP-OES), and the data using analysis of variance (ANOVA), Pearson correlation and Principal Component Analysis (PCA). All presented values outside those established by Brazilian legislation, with an average of 267.2 ug/L. ANOVA showed role of seasonality in the concentrations of the metals, with the periods of flooding in the basin having the lowest concentrations of metals. Such as Barium (Ba) and Beryllium (Be) with averages close to 0.0 ug/L in the flood period, and dry period with average values of 0.50 ug/L. The correlation showed the relationship of Ba, Be and Titanium (Ti) with the Biochemical Oxygen Demand (BOD). PCA indicated the metals Ba, Be and Ti as the most relevant contaminants in the basin. It was possible to develop a map to identify the sampling points where the concentrations of these metals are the highest. Keywords: Surface water, toxic metals, urban basin, water contaminants.