Contaminação por elementos-traço em ecossistemas lênticos urbanos brasileiros: tendências nacionais e padrões locais

Abstract

Urban lentic environments, such as lakes and reservoirs, are particularly vulnerable to trace element contamination due to their low hydrodynamics and, consequently, high capacity for pollutant retention. These contaminants, originating from both natural and anthropogenic sources, pose ecological and public health risks. Therefore, we investigated trace element contamination in Brazilian urban lentic ecosystems using two complementary approaches. In the first chapter, we conducted a systematic review of scientific literature published between 1980 and 2023, aiming to understand how these contaminants are studied across different Brazilian regions, considering the country's vast geographical, environmental, and socioeconomic diversity. Studies were categorized according to geographic region, biome, land use type, trace elements investigated, matrix analyzed, and references to Brazilian environmental legislation. We observed a growing trend in scientific production, especially between 2011 and 2023. Most studies were conducted in industrial areas, mainly in the Southeast region, large urban centers, and the Atlantic Forest biome. The most frequently investigated trace elements were Cu, Pb, Cr, Zn, and Ni, with sediment being the most commonly analyzed matrix. In the second chapter, we analyzed the spatial distribution of trace elements in the sediments of the Ibirité Reservoir (Minas Gerais), an artificial reservoir located in an urbanized watershed, and its tributaries. Concentrations of As, Cu, Cd, Cr, Hg, Mn, Ni, Pb, and Zn were quantified at 22 sampling points during two campaigns (dry and wet seasons), along with physical, chemical, and granulometric characteristics of the sediments. Concentrations of As, Ni, Cu, Pb, and Cr in the reservoir exceeded the limits established by Brazilian Resolution CONAMA n° 454/2012. In the tributaries, trace element concentrations were associated with land use and land cover, indicating a direct influence of anthropogenic activities in the drainage basins. In contrast, in the reservoir, land use and land cover were not good predictors of the spatial distribution of contaminants; instead, sediment characteristics, especially the proportion of fine particles, were the main factors related to trace element concentrations. The results of this work contribute to a better understanding of trace element contamination in urban lakes and may support monitoring and environmental management strategies in these ecosystems.