The rupture of Brazil's Fundão Dam in November 2015, known as the largest environmental disaster in the country's history, resulted in the immediate release of approximately 40 million cubic meters of iron ore tailings into the environment. This catastrophe had widespread and devastating effects, contaminating water bodies, disrupting ecosystems, displacing communities, and raising long-term health and environmental concerns. It underscores the necessity of stringent safety measures and responsible environmental management in the mining industry and the ongoing need for remediation and restoration efforts.

The present study sought to evaluate the relationship between sediment characteristics and land use within the Water Resources Planning and Management Unit (UPGRH) of the “Piranga River”, Minas Gerais. This river represents one of the most crucial sub-basins of the “Doce River” in Brazil. The Piranga River was the first basin affected by the Iron Dam Break. Sediments in this context are complex geochemical entities that yield information essential for understanding the interactions of various processes occurring in fluvial environments. They originate from both natural soil weathering processes and anthropogenic activities, making them integral components of the watershed.

Bottom sediments serve as indicators of the environmental impacts resulting from the improper disposal of domestic and industrial effluents in ecosystems. This study entailed two campaigns conducted in June 2019 and March 2020, during which a total of 14 samples were collected from pre-defined locations within the UPGRH of the Piranga River. This area had been significantly affected by a dam disaster involving the mining company Samarco in the municipality of Mariana, Minas Gerais. Subsequently, the collected samples were subjected to drying, homogenization, sieving, and digestion processes. The grain size analysis results, obtained for both dry and rainy seasons, revealed that sediments from the region affected by the Samarco disaster exhibited finer grain sizes compared to those from unaffected rivers that were also assessed. This grain size analysis corresponded with the specific land use in these areas, as exemplified by the sampling point in the Casca River, which featured a coarser sand-related grain size and was known for such activity.

In summary, this research aimed to elucidate the extent to which human activities within a watershed can impact water quality and, consequently, sediment quality.