Estudo da distribuição e do potencial de metilação do mercúrio em solos e sedimentos de áreas a serem inundadas para aproveitamento hidrelétrico
Carregando...
Arquivos
Data
2014-08-01
Autores
Gomes, Vinícius Marques [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Desde o final dos anos 80, a questão do comportamento do mercúrio no ambiente amazônico e sua toxicidade vêm sendo discutidos por pesquisadores brasileiros e estrangeiros na tentativa de se determinar o verdadeiro risco que este elemento apresenta para o ecossistema. Embora muitos avanços tenham sido obtidos num intenso esforço de três décadas, a ausência de um grande programa de mapeamento e monitoramento da contaminação por mercúrio em todo território amazônico dificulta a precisa determinação dos caminhos que este metal percorre antes de constituir um perigo ao ser humano. No ambiente aquático, o mercúrio pode ser metilado por processos biológicos e/ou químicos. Dentre as espécies de mercúrio, o metilmercúrio (MeHg) é a mais tóxica, o que se deve a sua elevada estabilidade, solubilidade lipídica e propriedades iônicas que lhe permite atravessar membranas de organismos vivos. A metilação do mercúrio e o subsequente acúmulo na biota é maior no ambiente aquático que no terrestre e pode ser considerada a etapa chave para o entendimento do ciclo do Hg. O interesse no estudo ecotoxicológico do MeHg se deve principalmente ao fato de ser uma neurotoxina, tendo a tendência de bioacumular e biomagnificar, tornando-se um risco para a saúde humana. A principal via de contaminação nos seres humanos é através da ingestão de alimentos, principalmente peixes. Neste trabalho, foi realizado um estudo na região no do rio Madeira na área de influência da Usina Hidrelétrica de Jirau, determinando a concentração de mercúrio total e orgânico em amostras de água, solo e sedimento, e verificou-se que tais valores estão abaixo dos níveis preconizados pela legislação brasileira, não evidenciando contaminação pontual deste metal na bacia antes do enchimento do lago. Além disso, estudou-se a formação do MeHg utilizando águas, solos e sedimentos provenientes de três bacias da região amazônica (águas claras – rio Tocantins GO, águas brancas – rio Madeira RO e águas escuras – rio Negro AM), na presença de Hg0 e Hg2+ ao longo de 25 dias, analisando pH, condutividade, potencial redox (EH) e oxigênio dissolvido (OD), verificando uma relação inversamente proporcional entre formação de mercúrio orgânico e os parâmetros medidos durante o estudo.
Since the end of the 1980s, the behavior of mercury in the Amazonian environment, as well as its potential toxicity, has been investigated by scientists from both Brazil and elsewhere in order to try to determine the true risks that this element poses to the ecosystem and human health. Despite substantial advances over three decades, the absence of adequate mapping and monitoring of mercury contamination throughout the Amazon region has hindered identification of the precise routes by which the metal is transported before it could constitute a hazard to humans. In the aquatic environment, mercury can be methylated in biological and chemical processes. Amongst the various mercury species, methylmercury (MeHg) is the most toxic, due to its high stability, lipid solubility, and ionic properties, which enable it to traverse the membranes of living organisms. The methylation of mercury and its subsequent accumulation in biota is greater in the aquatic than in the terrestrial environment, and it is vital to understand this key step in the Hg cycle. Interest in ecotoxicological studies of MeHg is largely driven by the fact that the compound is a neurotoxin that can become bioaccumulated and biomagnified, and therefore represent a threat to human health. The main route for human uptake of MeHg is through the ingestion of foods, especially fish. The present work concerns a study of a region of the Madeira River influenced by the Jirau hydroelectric facility. The concentrations of total and organic mercury were determined in samples of water, soil, and sediment. The values obtained were below the permissible levels established by Brazilian legislation, and there was no evidence of contamination in the river basin due to emissions of mercury from point sources, prior to filling of the reservoir. Investigation was also made of the formation of MeHg, employing water, soil, and sediment obtained from three basins in the Amazon region, characterized by the presence of clear water (Tocantins River in Goiás State), white water (Madeira River in Rondônia), and black water (Negro River in Amazônia). The experiments were performed over a period of 25 days, using Hg0 and Hg2+, with measurement of pH, conductivity, redox potential (EH), and dissolved oxygen (DO). Inversely proportional relationships were observed between the formation of organic mercury and the measured parameters.
Since the end of the 1980s, the behavior of mercury in the Amazonian environment, as well as its potential toxicity, has been investigated by scientists from both Brazil and elsewhere in order to try to determine the true risks that this element poses to the ecosystem and human health. Despite substantial advances over three decades, the absence of adequate mapping and monitoring of mercury contamination throughout the Amazon region has hindered identification of the precise routes by which the metal is transported before it could constitute a hazard to humans. In the aquatic environment, mercury can be methylated in biological and chemical processes. Amongst the various mercury species, methylmercury (MeHg) is the most toxic, due to its high stability, lipid solubility, and ionic properties, which enable it to traverse the membranes of living organisms. The methylation of mercury and its subsequent accumulation in biota is greater in the aquatic than in the terrestrial environment, and it is vital to understand this key step in the Hg cycle. Interest in ecotoxicological studies of MeHg is largely driven by the fact that the compound is a neurotoxin that can become bioaccumulated and biomagnified, and therefore represent a threat to human health. The main route for human uptake of MeHg is through the ingestion of foods, especially fish. The present work concerns a study of a region of the Madeira River influenced by the Jirau hydroelectric facility. The concentrations of total and organic mercury were determined in samples of water, soil, and sediment. The values obtained were below the permissible levels established by Brazilian legislation, and there was no evidence of contamination in the river basin due to emissions of mercury from point sources, prior to filling of the reservoir. Investigation was also made of the formation of MeHg, employing water, soil, and sediment obtained from three basins in the Amazon region, characterized by the presence of clear water (Tocantins River in Goiás State), white water (Madeira River in Rondônia), and black water (Negro River in Amazônia). The experiments were performed over a period of 25 days, using Hg0 and Hg2+, with measurement of pH, conductivity, redox potential (EH), and dissolved oxygen (DO). Inversely proportional relationships were observed between the formation of organic mercury and the measured parameters.
Descrição
Palavras-chave
Quimica analítica e quimica ambiental, Mercurio, Solos, Usinas hidrelétricas, Agua, Metilmercurio, Analytical chemistry
Como citar
GOMES, Vinícius Marques. Estudo da distribuição e do potencial de metilação do mercúrio em solos e sedimentos de áreas a serem inundadas para aproveitamento hidrelétrico: Vinicius Marques Gomes. -. 2014. 99 f. Tese (doutorado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Química de Araraquara, 2014.