Abstract
In 2015, the Fundão dam collapse released about 50 million m3 of tailings into the Rio Doce basin (BRD), impacting ecosystems from the river to the coast. Even after a decade, these residues persist in the basin’s soils and sediments. Although traditional environmental risk assessments provide important insights, their reliance on enrichment indices and exchangeable fractions fails to measure mobility dynamics in complex systems.
Using the DRB disaster as a case study, we explore how diffusion rates govern the transport of Potentially Toxic Elements (PTE) from the tailings sludge to the underlying soil profiles. By determining the diffusion coefficients (D), mobilization is analyzed from a kinetic perspective, allowing us to simulate the migration of contaminants such as arsenic (As), lead (Pb), chromium (Cr), and nickel (Ni) over decades. The discussion addresses integrating this mathematical model with the physicochemical properties of the medium — such as pH, texture, organic matter content, and ionic charge — to predict subsurface contamination.
The experimental results showed D values ranging from 3.82±0.65×10-12 m2.s-1 for Pb to 8.96±2.53×10-12 m2.s-1 for As, evidencing the thermodynamic viability of the migration of these ions from the tailings sludge to the soil subsurface. The analysis of the diffusion profiles indicated distinct behaviors among the contaminants: while Pb and Ni are fitted by simple Gaussian models, As and Cr required a double model. This differentiation suggests the existence of multiphase transport regimes or variations in oxidation states for As and Cr, whereas Pb and Ni exhibited more homogeneous diffusion patterns. Integrating these coefficients into the generation of 3D response surfaces enabled spatiotemporal visualization of the contamination plume, establishing a dynamic diagnostic tool for the management of environmental liabilities.
Biography
Dr. Letícia Alana Bertoldo is a researcher and PhD-level chemist specializing in the development of nanostructured materials for environmental remediation and risk assessment in soil matrices. With a robust background in Environmental Chemistry, Dr. Bertoldo has conducted critical investigations into the impacts of the Mariana (MG) mining disaster on the Doce River Basin, employing sequential extraction techniques and diffusion studies to diagnose contaminant mobility. She currently serves as a Professor in professional education, teaching courses in Analytical Chemistry and Environmental Chemistry. Dr. Bertoldo has authored several articles in high-impact international peer-reviewed journals, contributing significantly to the advancement of sustainable analytical chemistry and environmental safety.