Toxicidade de sedimentos superficiais de reservatórios paulistas: uma abordagem espacial com uso de Danio rerio
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2022-10-27
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Universidade Estadual Paulista (Unesp)
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Os reservatórios do Estado de São Paulo estão cercados por grandes centros urbanos, empreendimentos agrícolas e industriais, sofrendo a influência destas atividades, como a poluição difusa, descarte de lixo sólido e, principalmente, o despejo de esgoto in natura. A aplicação de sulfato de cobre é uma prática comum em alguns desses reservatórios, para o controle de florações algais. Os sedimentos acumulam compostos e contaminantes, deste modo, são importantes na avaliação da qualidade dos corpos d’água. O presente trabalho teve por objetivo avaliar a toxicidade dos sedimentos, através de ensaios ecotoxicológicos com o peixe Danio rerio, análises histopatológicas dos órgãos-alvo, concentração de metais bioacumulados nos peixes e das análises físico-químicas dos sedimentos superficiais dos reservatórios Broa, Itupararanga, Guarapiranga e Rio Grande, com o intuito de determinar o gradiente de qualidade para estes corpos hídricos. Nos reservatórios foram tomadas amostras de sedimento em triplicata em três zonas distintas, fluvial, central e barragem, em três pontos distintos de cada zona, totalizando 27 amostras. Métodos analíticos padronizados foram utilizados para avaliação dos teores de matéria orgânica, frações granulométricas e concentrações dos metais cádmio, chumbo, cobre, cromo, níquel e zinco, determinação da bioacumulação dos metais e lesões histopatológicas de brânquias, fígado e rins. Os valores obtidos dos metais foram comparados com o protocolo de qualidade de sedimento para proteção da vida aquática. Foram realizados ensaios crônicos de toxicidade com sedimentos dos quatro reservatórios, em delineamento experimental com grupo controle e três repetições para cada ponto dos reservatórios. O cobre foi significativo para a mortalidade dos D. rerio, as mortalidades ocorreram nas amostras próximas das barragens do Guarapiranga e Rio Grande, enquanto nos reservatórios Itupararanga e Broa não ocorreram mortalidades. As lesões regressivas foram as mais observadas, em diferentes graus nos três órgãos analisados. Foram observadas alterações em lamelas primárias e secundárias, acúmulos de pigmentos em fígado e rins. Foram encontradas concentrações 100 vezes maior de cobre do que o background do corpo hídrico, demonstrando que a gestão influencia no nível de toxicidade dos sedimentos. Os resultados aqui apresentados poderão subsidiar e embasar tomadas de decisões sobre o gerenciamento de áreas com importância socioambiental.
Reservoirs in the State of São Paulo are surrounded by large urban areas, agricultural and industrial enterprises, suffering the influence of these activities, such as, diffuse pollution, solid waste disposal and, mainly, sewage disposal in natura. Copper sulfate application is a common practice in some reservoirs, for algal bloom control. Sediments accumulate compounds and contaminants, this sense, they are important in water body quality assessment. This study was aimed to evaluate the sediment toxicity, through ecotoxicological assays with Danio rerio (fish), histopathological analyses of target organs, concentration of bioaccumulated metal in fish and, physical-chemical analyses on the superficial sediment in Broa, Itupararanga, Guarapiranga and Rio Grande reservoirs, in order to determine the quality gradient for these water bodies. Triplicate sediment samples were taken in three different zones along the reservoirs, entrance, central and dam, with three different sites in each zone, with a total of 27 sampling sites. Standard analytical methods were used to evaluate organic matter content, granulometric fractions and metal concentration (Cd, Cu, Cr, Ni, Pb, Zn), metal bioaccumulation and histopathological injuries in gills, liver and kidneys. Metal values were compared to sediment quality protocol for aquatic life protection. Toxicity chronical assays were performed using the sediment collected in the four reservoirs, the experimental design consisted of a control group and three repetitions for each sampling site. Copper was significative for the survival of D. rerio, mortalities occurred with samples collected near the dam in Guarapiranga and Rio Grande, meanwhile Itupararanga and Broa sediments no mortalities were reported. Regressive injuries were the most spotted, in different degrees in the three organs analyzed. Changes were observed in primary and secondary lamellae, pigment accumulations in liver and kidneys. One-hundred-fold concentrations higher than the background were found, demonstrating that the management influences the toxicity level of sediments. Results presented here will supply the decision-making process about the management of important socio-environmental areas.
Reservoirs in the State of São Paulo are surrounded by large urban areas, agricultural and industrial enterprises, suffering the influence of these activities, such as, diffuse pollution, solid waste disposal and, mainly, sewage disposal in natura. Copper sulfate application is a common practice in some reservoirs, for algal bloom control. Sediments accumulate compounds and contaminants, this sense, they are important in water body quality assessment. This study was aimed to evaluate the sediment toxicity, through ecotoxicological assays with Danio rerio (fish), histopathological analyses of target organs, concentration of bioaccumulated metal in fish and, physical-chemical analyses on the superficial sediment in Broa, Itupararanga, Guarapiranga and Rio Grande reservoirs, in order to determine the quality gradient for these water bodies. Triplicate sediment samples were taken in three different zones along the reservoirs, entrance, central and dam, with three different sites in each zone, with a total of 27 sampling sites. Standard analytical methods were used to evaluate organic matter content, granulometric fractions and metal concentration (Cd, Cu, Cr, Ni, Pb, Zn), metal bioaccumulation and histopathological injuries in gills, liver and kidneys. Metal values were compared to sediment quality protocol for aquatic life protection. Toxicity chronical assays were performed using the sediment collected in the four reservoirs, the experimental design consisted of a control group and three repetitions for each sampling site. Copper was significative for the survival of D. rerio, mortalities occurred with samples collected near the dam in Guarapiranga and Rio Grande, meanwhile Itupararanga and Broa sediments no mortalities were reported. Regressive injuries were the most spotted, in different degrees in the three organs analyzed. Changes were observed in primary and secondary lamellae, pigment accumulations in liver and kidneys. One-hundred-fold concentrations higher than the background were found, demonstrating that the management influences the toxicity level of sediments. Results presented here will supply the decision-making process about the management of important socio-environmental areas.
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Reservatórios, Toxicidade, Danio rerio, Histopatologia, Cobre, TEL e PEL