Mapeamento de índices geoquímicos para detecção de contaminações ambientais por metais pesados e fósforo na região do Quadrilátero Ferrífero - MG

Abstract

Geochemical mapping has been employed in various countries with diverse objectives, serving as a critical tool for identifying the geochemical characteristics of the environment. This study focuses specifically on the following map sheets: Belo Horizonte (SE-23-Z-C-VI), Igarapé (SF-23-X-A-III), and Ouro Preto (SF-23-A-II), encompassing a total area of 8,700 km². The main objective of this research is to generate environmental indices for seven elements with high environmental and human toxicity. A total of 589 active stream sediment samples were analyzed, collected during the "Geochemistry of the Quadrilateral Ferriferous and Its Surroundings" project conducted by SBGEO – Geological Survey of Brazil. The data was processed using univariate descriptive statistical techniques and categorized by their geological unit, based on sample locations. The study produced 21 enrichment factor maps with different normalizers, 7 contamination factor maps 3 maps for ecological potential risk index and 3 maps for modified contamination degree, all compared to known regional and global background values. The results indicate that the efficiency of the applied normalizers varies according to used chemical elements, influenced mainly by geogenic factors. When compared to global or regional averages, the values reveal numerous anomalies that are questionable, as they do not reflect the actual geochemical concentrations of the Quadrilateral Ferriferous. Consequently, these comparisons yield unsatisfactory information for the region. Better results were achieved when analyses were based on local background values calculated from the geological units of the study area.