Rapid and low-Cost geochemical indices for tracing iron mining tailings within fluvial sediments: a case study from the Paraopeba River after the B1 Dam burst in Brumadinho, Minas Gerais, Brazil

Fernando Pantuzzo¹Fernando Laureano²Caíque Cabral³Gabriel Negreiros Salomão⁴Roberto Dall’Agnol⁴Vitor Pimenta²Lucas Pereira Leão^5*

• ¹SRK Consulting, Belo Horizonte, Brazil
• ²Vale S.A., Belo Horizonte, Brazil
• ³Arcadis, Belo Horizonte, Brazil
• ⁴Vale Technological Institute (ITV), Belém, Pará, Brazil
• ⁵Universidade Federal de Ouro Preto, Ouro Preto, Brazil

The B1 dam failure at Córrego do Feijão mine in Brumadinho (Minas Gerais, Brazil) in January 2019 caused severe, long-lasting environmental impacts, particularly on the fluvial sediments of the Paraopeba River basin. Characterizing the geochemical signature of the iron tailings and distinguishing these materials from the river’s natural sediments remains a significant challenge. This study investigates the geochemical signatures of major and minor elements in sediments affected by the tailings and proposes geochemical indices capable of identifying tailings in impacted sediments. Six cores were extracted along the Paraopeba River bedload. A total of 54 samples were collected and subjected to X-ray fluorescence analysis to determine major and minor elements (Al2O3, CaO, Fe, MgO, Mn, P, SiO2, TiO2). The main constituents in natural sediment samples were SiO2 and Al2O3, together accounting for 52.7% to 96.6%, while Fe2O3 represented 1.1% to 42.7%. Conversely, in tailings samples, Fe2O3 ranged from 36.6% to 88.8%, followed by silica (8.4% to 34.4%) and alumina (0.87% to 19.1%). Fe2O3 levels were above 60% in most tailings samples. Natural sediment samples generally had higher TiO2, CaO, and MgO content, whereas tailings showed higher MnO and P2O5. Based on these data, we proposed two chemical indices, IRS1 and IRS2, which are rapid and low-cost to calculate. Due to compositional characteristics, IRS values spread diagonally when plotted on a binary IRS1 x IRS2 graph. The indices were applied to stream sediment samples from the Paraopeba River, collected in 2019 during the Emergency Monitoring Program. The results indicated that tailings samples were concentrated upstream of the UTE Igarapé reservoir spillway, reinforcing the reservoir’s role in reducing tailings propagation along the river. Moreover, when applied to stream sediment samples collected in 2023 from affected areas subjected to dredging, low IRS1 and IRS2 values were observed. Thus, considering the large dataset from sediment monitoring in the Paraopeba River basin, the proposed indices serve as a graphical tool for tracking tailings dispersion over space and time.