Water Quality and Anthropogenic Impacts in the Brazilian Amazon: A Systematic Review of Physicochemical Parameters

This study provides a systematic review of water quality in the Brazilian Amazon Basin, synthesizing evidence on physicochemical conditions and anthropogenic pressures. We searched major international databases (2014–2024) using predefined criteria and rigorous screening. Of 77 records, 3 met eligibility standards and were included for quantitative synthesis. Extracted data covered standardized physicochemical parameters and trace metals. Water quality showed marked spatial and seasonal variability, with generally lower pH in the dry season (range 5.2–8.1) and higher turbidity and organic load in urbanized reaches. Rivers influenced by untreated effluents exhibited elevated BOD and coliforms, while catchments affected by mining displayed critical mercury burdens. In contrast, less impacted reaches maintained comparatively better conditions. Across studies, riparian vegetation emerged as a consistent mitigating factor, buffering temperature and reducing metal availability. Overall, Amazonian water quality patterns track gradients of land use and sanitation deficits, posing risks to aquatic biota and human health. We highlight the need to combine riparian-forest protection with expanded wastewater infrastructure and long-term monitoring to inform policy and management, aligned with sustainable-development targets. Graphic abstract