Ponente
Descripción
The intensification of illegal gold mining activities in the Amazon has increased the environmental impacts associated with mercury contamination in river systems, especially in the Madeira River, a tributary of the Amazon River. In this context, this study presents a mathematical model based on difference equations to describe the propagation of mercury along the stretch between Porto Velho and Calama, in the state of Rondônia, Brazil. The main objective is to analyze the spatiotemporal behavior of mercury concentration in the river, considering processes of advection, dispersion, decay, and external inputs related to mining activities. The study is structured around the formulation of a linear system of difference equations applied to compartments (Porto Velho, São Carlos, Nazaré, and Calama), locations along the Madeira River. The dynamics are described by recurrence relations of the form $C_{i,n+1}=C_{i,n}+f_{i-1}C_{i-1,n}-f_iC_{i,n}-d_iC_{i,n}+Q_i$ where $f$ represents advection coefficients between compartments, $d$ represents bed deposition factors, and $Q$ represents external inflows from mining activity. Simulations of hydrological scenarios for flood and drought conditions, as well as different intensities of mining activity, were implemented. The model parameters were calibrated using official data from the National Water and Basic Sanitation Agency (ANA, Water Resources Situation in Brazil, ANA, 2024), as well as toxicological and environmental studies on mercury in the Amazon (Bastos, W.R. & Lacerda, L.D., Geochim. Bras. 18, 99–114, 2004; Fiocruz, Mercury in the Amazon: introductory aspects on surveillance and monitoring in exposed and potentially exposed Indigenous populations, Fiocruz, 2026; Lombardi, S. et al., Environ. Sci. Pollut. Res. 29, 22401–22415, 2022). In addition, geochemical studies on the mercury cycle in the Amazonian environment (Wasserman, J.C. et al., Ambio 32, 336–342, 2003) and environmental studies applied to mining (Oliveira, H.S.P. et al., Geochim. Bras. 26, 143–154, 2012) were considered. The modeling accounts for transfer coefficients between river sections, deposition factors, and external loads from artisanal mining. The results showed that scenarios with higher river flow favor the propagation of mercury among the analyzed sections, while dry periods tend to increase the local concentration of the contaminant, heightening environmental and social risks to riverine populations. This demonstrates that increased artisanal mining activities significantly intensify the simulated levels of contamination, especially in areas closest to the discharge points. Addressing real-world problems such as this one aligns directly with the United Nations (UN) Sustainable Development Goals (SDGs), particularly SDG 3 (Good Health and Well-being), SDG 6 (Clean Water and Sanitation), SDG 13 (Climate Action), and SDG 15 (Life on Land), shedding light on the impacts on public health, water security, biodiversity, and vulnerable populations in the Amazon. Finally, the potential of mathematical modeling as an interdisciplinary tool for analyzing complex socio-environmental issues is highlighted, integrating Applied Mathematics, environmental sciences, and public and educational policies.