Avaliação toxicogenética de amostras ambientais de uma área de mineração de ouro (Paracatu-MG) contaminada com arsênio e outros metais
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Data
2019-09-27
Autores
Corroqué, Nádia Aline [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O crescente aumento das atividades antrópicas vem promovendo um aumento nos impactos causados ao meio ambiente. Dentre essas atividades humanas, a mineração, realizada no Brasil desde o século XVII e persistindo até os dias atuais, tem se destacado, quanto à sua potencialidade de causarem danos ambientais. O estado de Minas Gerais é um grande produtor de ouro e nele está localizado o município de Paracatu, onde se encontra a mina Morro do Ouro, que é considerada uma grande lavra a céu aberto, situada a poucos metros do perímetro urbano. Diante deste cenário, o presente estudo tem por objetivo avaliar a biodisponibilidade dos metais presentes nas amostras, as fontes poluidoras envolvidas com a contaminação desses metais e os riscos que esses metais promovem ao meio ambiente, por meio das análises químicas, extrações sequenciais e cálculos de Fator de Enriquecimento (EF), Índice de geoacumulução (Igeo) e Avaliação de Risco (RAC) e o potencial tóxico das amostras, por meio de bioensaios in vivo (Allium cepa e Lactuca sativa) e in vitro (cultura celular humana – HepG2/C3A). Para a avaliação do comprometimento dos rios que recebem influência da mineradora, foram coletadas amostras de água superficiais e de sedimentos de 3 regiões distintas: 1) jusante da mina Morro do Ouro, onde está localizado o município de Paracatu (P1, P2 e P3); 2) jusante da barragem de rejeitos da mina Morro do Ouro (P4, P5 e P6) e 3) rio de captação de água para abastecimento público de Paracatu (P7) e água de abastecimento fornecido pela ETA de Paracatu (P8). Também foram preparados dois extratos dos sedimentos coletados (solubilizado e lixiviado). Os resultados mostraram que essa região é altamente enriquecida com metais provenientes da própria constituição das rochas, no entanto, as atividades antrópicas, como as da mineradora, estão aumentando a biodisponibilização desses elementos no ambiente. Os bioensaios com A. cepa mostraram citotoxicidade e genotoxicidade para todas as amostras de água e genotoxicidade para todas as amostras de sedimento. Potencial mutagênico foi observado em algumas amostras de água (P2, P5 e P7) e sedimento (P2, P3 e P8), assim como citotoxicidade para sedimentos (P6 e P7). Para os bioensaios com L. sativa, nenhuma das amostras, nem de água, nem de sedimento, interferiram na taxa de germinação. Apenas as amostras do ponto P3 (solubilizado) induziram diminuição da germinação. Já para o desenvolvimento das sementes de L. sativa, as amostras de água induziram diminuição no crescimento de hipocótilo e da raiz (P1, P6 e P8) e as amostras de sedimento diminuição do crescimento de hipocótilo (P1, P2, P3 e P5). Para os extratos solubilizado e lixiviado, foi observado um aumento no crescimento de raiz, para os dois extratos do ponto P4, mas não houve alteração no crescimento do hipocótilo. Os ensaios de viabilidade celular com o corante Azul de Tripan, realizados com cultura celular HepG2/C3A, mostraram que as células foram mais sensíveis ao extrato solubilizado do que ao lixiviado. O ensaio do cometa, realizado pela exposição às amostras de água e sedimento (solubilizado), mostrou genotoxicidade apenas para o ponto P6 (solubilizado). A ausência de genotoxicidade nos demais pontos ocorreu, provavelmente, devido a um maior efeito citotóxico dessas amostras. O ensaio do MN com bloqueio de citocinese mostrou que todas as amostras de sedimento (solubilizado) foram genotóxicas, além de altamente citotóxicas, por ter elevados os índices de morte celular e de proliferação celular, enquanto mutagenicidade foi observada somente para as amostras dos pontos P2 e P3. Diante desses resultados, pode-se concluir que a mineração do Morro do Ouro possui alta potencialidade de causar danos aos ecossistemas dos corpos d’água e também aos humanos que vivem nessa área de estudo.
The increase of anthropic activities has been promoting an impact increase to the environment. Among these human activities, mining, conducted in Brazil since the XVII century, has stood out for its potential to cause environmental damage. The Morro do Ouro mine, located in Paracatu (state of Minas Gerais, considered a major gold producer) is a large open mining located a few meters from the urban perimeter. According to this scenario, the present study aims to evaluate the bioavailability of the metals present in the samples, the polluting sources involved with the contamination of these metals and the risks that these metals promote to the environment by chemical analysis, sequential extractions and calculations of Enrichment Factor (EF), Geoaccumulation Index (Igeo) and Risk Assessment (RAC) and the toxic potential of samples by in vivo (Allium cepa and Lactuca sativa) and in vitro bioassays (human cell culture - HepG2 / C3A).To evaluate the impact of rivers that receive influence from the mining company, surface water and sediment samples were collected from 3 different regions: 1) downstream of the Morro do Ouro mine, located in Paracatu (P1, P2 and P3); 2) downstream of the Morro do Ouro tailings dam (P4, P5 and P6) and 3) Paracatu water supply river (P7) and water supply provided by Paracatu WTS (Water Treatment Station) (P8). Afterwards, two extracts of eachcollected sediments (solubilized and leached) were prepared. The results demonstrated that this region is highly enriched with metals naturally derived from the rocks, however, anthropic activities, such as those of the mining company, are increasing the bioavailability of these elements in the environment. Allium cepa bioassays showed cytotoxicity and genotoxicity of the water samples and genotoxicity of the sediment samples. Furthermore, mutagenic potential was observed at some points (water: P2, P5 and P7; sediment: P2, P3 and P8). For sediment samples, cytotoxicity was also observed, but only at points P6 and P7. On the other hand, for Lactuca sativa bioassays, neither water nor sediment interfered with the germination rate. Only the samples of point P3 (solubilized) induced decreased germination. For the development of L. sativa seeds, water samples induced decrease in hypocotyl and root growth (P1, P6 and P8) and sediment samples decreased hypocotyl growth (P1, P2, P3 and P5). For solubilized and leachate extracts, an increase in root growth was observed for both P4 point extracts, but there was no change in hypocotyl growth. Cell viability assays with the Trypan Blue, performed with HepG2/C3A cell culture, showed that the cells were more sensitive to the solubilized extract than the leachate extract. The comet assay, performed with water and sediment samples (solubilized), showed genotoxicity only for point P6 (solubilized). The absence of genotoxicity at the other points was probably due to a greater cytotoxic effect of these samples. The cytokinesis blocking MN assay showed that all the sediment samples (solubilized) were genotoxic as well as highly cytotoxic, since they presented high cell death and cell proliferation rates, while mutagenicity was observed only in P2 and P3 samples. According to these results, we can conclude that the mining of Morro do Ouro has high potential to cause damage to water bodies ecosystems and also to humans who live in the area.
The increase of anthropic activities has been promoting an impact increase to the environment. Among these human activities, mining, conducted in Brazil since the XVII century, has stood out for its potential to cause environmental damage. The Morro do Ouro mine, located in Paracatu (state of Minas Gerais, considered a major gold producer) is a large open mining located a few meters from the urban perimeter. According to this scenario, the present study aims to evaluate the bioavailability of the metals present in the samples, the polluting sources involved with the contamination of these metals and the risks that these metals promote to the environment by chemical analysis, sequential extractions and calculations of Enrichment Factor (EF), Geoaccumulation Index (Igeo) and Risk Assessment (RAC) and the toxic potential of samples by in vivo (Allium cepa and Lactuca sativa) and in vitro bioassays (human cell culture - HepG2 / C3A).To evaluate the impact of rivers that receive influence from the mining company, surface water and sediment samples were collected from 3 different regions: 1) downstream of the Morro do Ouro mine, located in Paracatu (P1, P2 and P3); 2) downstream of the Morro do Ouro tailings dam (P4, P5 and P6) and 3) Paracatu water supply river (P7) and water supply provided by Paracatu WTS (Water Treatment Station) (P8). Afterwards, two extracts of eachcollected sediments (solubilized and leached) were prepared. The results demonstrated that this region is highly enriched with metals naturally derived from the rocks, however, anthropic activities, such as those of the mining company, are increasing the bioavailability of these elements in the environment. Allium cepa bioassays showed cytotoxicity and genotoxicity of the water samples and genotoxicity of the sediment samples. Furthermore, mutagenic potential was observed at some points (water: P2, P5 and P7; sediment: P2, P3 and P8). For sediment samples, cytotoxicity was also observed, but only at points P6 and P7. On the other hand, for Lactuca sativa bioassays, neither water nor sediment interfered with the germination rate. Only the samples of point P3 (solubilized) induced decreased germination. For the development of L. sativa seeds, water samples induced decrease in hypocotyl and root growth (P1, P6 and P8) and sediment samples decreased hypocotyl growth (P1, P2, P3 and P5). For solubilized and leachate extracts, an increase in root growth was observed for both P4 point extracts, but there was no change in hypocotyl growth. Cell viability assays with the Trypan Blue, performed with HepG2/C3A cell culture, showed that the cells were more sensitive to the solubilized extract than the leachate extract. The comet assay, performed with water and sediment samples (solubilized), showed genotoxicity only for point P6 (solubilized). The absence of genotoxicity at the other points was probably due to a greater cytotoxic effect of these samples. The cytokinesis blocking MN assay showed that all the sediment samples (solubilized) were genotoxic as well as highly cytotoxic, since they presented high cell death and cell proliferation rates, while mutagenicity was observed only in P2 and P3 samples. According to these results, we can conclude that the mining of Morro do Ouro has high potential to cause damage to water bodies ecosystems and also to humans who live in the area.
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Palavras-chave
Toxicidade, Biomonitoramento, Sedimento, Água, Citotoxicidade, Genotoxicidade, Mutagenicidade, In vivo, In vitro, Toxicity, Biomonitoring, Sediment, Water, Cytotoxicity, Genotoxicity, Mutagenicity