A water quality index has not been developed for Amazonian blackwater rivers. In this paper, we used data collected in recent years to address this gap. An index was constructed using, in total, 342,930 analyses involving 161 water quality parameters. All analyses were part of ten large-scale campaigns, which took place between 2021 and 2023. The modifications proposed by the adoption of the new WQI enabled changes in the water quality results of the Amazon region, in comparison with an index used in other parts of Brazil. The proposal is a long-awaited tool that can significantly assist in the next stage in the preservation of this vast national wealth, which is the Amazon basin.

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.

Indicator bacteria, such as thermotolerant and fecal coliforms, particularly Escherichia coli, are employed as markers of water pollution, and their presence in water sources is attributed to human fecal contamination. The Puraquequara Basin in Manaus, AM, serves as case study due to its exposure to diverse anthropogenic activities. Its contaminants include microbial pollutants such as thermotolerant coliforms, fecal coliforms and other pathogenic bacteria. Predictive models for water quality monitoring provide an effective means of identifying microbiological hazards and assessing potential health risks. This study aims to develop a predictive statistical model for estimating thermotolerant coliform and Escherichia coli concentrations based on physicochemical water parameters in the Puraquequara Basin. The study was conducted over a 10-month period, from August 2022 to June 2023. A total of 68 samplings were performed, during which 20 physicochemical and microbiological water quality parameters were analyzed. The physicochemical and biological parameters were analyzed following the standardized methodologies recommended by the Standard Methods for the Examination of Water and Wastewater. A Multiple Linear Regression (MLR) model was developed to assess the influence of physicochemical parameters on E. coli and total coliform contamination in the Puraquequara Basin. The evaluated parameters suggest that the Puraquequara basin is undergoing a contamination process, making this natural environment conducive to microorganism development. The concentration graphs for coliforms and E. coli display human activities that occur more frequently, such as during the drier months when visitation increases, which elevates microbiological contaminant levels at the sampling points closest to these areas. The MLR analysis was statistically significant, although it demonstrated limited explanatory power for both total coliform (R² = 0.178, p <0.05) and I (R² = 0.220, p <0.05) analyses. Selected parameters for total coliform were statistically significant.

The city of Manaus has undergone an industrialization process that has negatively influenced the wastewater that makes up the urban part of the city. Monitoring water quality parameters and seasonal changes are essential for decision-making for the recovery of the basin's waters. The study evaluated, through the Water Quality Index (WQI) and multivariate statistical techniques, the seasonal and spatial variation in water quality in the Educandos basin, Manaus. The 14 sampling points were selected in the years 2020, 2021 and 2022. The analyzes followed the recommendations of the Stantard Methods for the Examination of Water and Wastewater. The IQA showed that seasonality has not been enough to cause an improvement in water quality. Cluster analysis ranked similar sample points in relation to water quality. The main component showed that turbidity, total solids and biological oxygen demand are the most relevant parameters for PC1, while for PC2 they were Total Coliforms, Total Nitrogen and pH. The multivariate analysis proved to be efficient for monitoring the basin, considering the process of environmental deterioration, resulting from the receipt of waste of mixed domestic and industrial origin.