Construção de mapas geoquímicos a partir de sedimentos ativos de margens oriundos do Rio Gualaxo do Norte, MG, Brasil

Abstract

Considerando que o mapeamento de recursos naturais podem subsidiar o estabelecimento de políticas de governo para o meio ambiente, de forma a contribuir com a utilização adequada dos recursos naturais, bem como possibilitar a melhoria na qualidade de vida, este estudo visou construir mapas de distribuição dos elementos Fe, As, Pb, Mn, Ba, Zn e Ni na bacia do rio Gualaxo do Norte, MG, Brasil. Para isso, foram coletadas 51 amostras de sedimentos ativos de margens ao longo da referida bacia. Em seguida, os resultados das análises químicas dessas amostras, em associação com os valores de background propostos para os elementos, foram utilizados para a construção de diferentes mapas geoquímicos, por meio do Sistema de Informações Geográficas (SIG). Os resultados obtidos evidenciam contribuições antropogênicas no enriquecimento de metais tais como Mn, Ba e Fe, assim como evidenciam que as contaminações por elevadas concentrações desses elementos podem extrapolar para bacias subsequentes à estudada, o que certamente agrava o problema de poluição identificado. Em adição, foi evidenciado que as atividades atuais de exploração aurífera na bacia, podem não estar disponibilizando concentrações elevadas de As e Pb, ambos metais altamente tóxicos, o que pode ser explicado pela diminuição considerável de exploração, quando comparada à exploração histórica na região.

River Water Contamination Resulting from the Mariana Disaster, Brazil

“…According to Parra et al (2007), the mining activity in the region of Quadrilátero Ferrífero has impacted the rivers by increasing the levels of suspended material and water turbidity. Furthermore, Rodrigues et al (2015) determined that fine-grained sediments of less than 63 μm, which contribute the most to heavy-metal content, may act as possible sources of contamination. This is because these metals are not permanently fixed, and are available throughout the water column due to changes in environmental conditions, such as variations in pH and redox potential, or the presence of organic chelators.…”

Evaluation of metal accumulation in the forage grass Brachiaria decumbens Stapf grown in contaminated soils with iron tailings

“…The highest concentrations of As and Cd were found in B. decumbens collected in the control area of Barra Longa, which may be related to the small‐scale gold mining near Barra Longa (Rodrigues, 2012; Rodrigues et al, 2015). The low concentrations of As found in B. decumbens shoots grown in affected areas could be explained by the low bioavailability of this element, which has been adsorbed in iron oxides from the tailing.…”

“…According to Rodrigues et al (2013b), the Zn content in sediments from alluvial terraces and cutbacks of this region is related to the natural occurrence of the sulfide-bearing rocks containing chalcopyrite and galena. However, most Zn in sediments is associated with the residual fractions and therefore is not bioavailable for plants (Rodrigues et al, 2015). Coelho et al (2020) also found higher concentrations of Zn in the control area (54.5 mg/kg), contrasting with averages of 20 mg/kg of zinc in the affected areas.…”

“…In addition to the environmental effects of the Samarco dam burst, the soils of the affected areas are naturally metalliferous. Thus, native and cultivated plants grown in this region can accumulate high levels of some metals in their tissues (Rodrigues et al, 2015; Schettini et al, 2018; Skirycz et al, 2014) regardless of being under the influence of contaminated substrates.…”

Mobility of metals in river sediments from a watershed in the Iron Quadrangle, Brazil

“…They are directly influenced by mining activities, leached to water bodies and co-precipitated, especially when carbonates are present in the area. Fine particles such as clay minerals present a sorting or ionic exchange capacity caused by the electric charges in their crystallographic structure (RODRIGUES et al, 2015a). The affinity of Cu 2+ with these minerals favors the adsorption process under the surface of carbonaceous minerals (FERREIRA; SANTANA, 2012).…”