Avaliação do grau de contaminação por traços metálicos das águas, sedimentos e dos camarões capturados nas lagoas do Imaruí e Mirim no Complexo Lagunar

• Ano de defesa: 2019
• Autor(a) principal: Silva, Cíntia Souza da
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Índice de qualidade da água; Sistema estuarino de Laguna; Metais pesados
• Link de acesso: https://repositorio.animaeducacao.com.br/handle/ANIMA/2491

The Lagunar complex is formed by eight lagoons: Lagoa da Garopaba do Sul, Manteiga, Camacho, Santa Marta, Ribeirão Grande, Santo Antônio, Imaruí and Mirim. One of the main activities in these lagoons is the shrimp fishing with net of trawl net, especially in the lagoons Imaruí and Mirim. The main tributary that flows into these lagoons is the Tubarão River, which drains mining regions with long extraction areas and tailings deposits from coal beneficiation. As a consequence of the drainage, migration of heavy metals to the lagoons, where the fish (prawns, fish and crab) are captured for commercial purposes. The objective of this work was to evaluate the degree of contamination by metallic traces of water, sediments and white prawns (penaeus schimitti) captured in lagoons of Imaruí and Mirim in the Lagunar complex, as water toxicity can have important implications for the aquatic ecosystem and public health. Monthly collections were carried out in the Imaruí and Mirim lagoons, from November 2017 to May 2018, and physical-chemical analyzes and trace elements of metals in the water, sediments and shrimp captured in the two lagoons were carried out. The results showed that the waters of Imaruí and Mirim lagoons can be classified as brackish class 1. In addition, all collection points presented GOOD/EXCELLENT water quality, with mean values for IQA of 78.83 for Imaruí lagoon and 78.14 for Mirim lagoon. It was also observed values for total biochemical oxygen demand (BOD >5 mg O2/L) below 3 mg.L-1, OD above 5 mg.L-1 and no presence of substances that produce color, odor, turbidity and floating materials were observed in the two lagoons. All metals analyzed in the water had concentrations below the maximum limits allowed by the legislation. The analyzes of the essential and non-essential metals showed that the most expressive values were obtained in the sediments, later in the shells and in the muscles of the shrimp. The Tukey test showed that the distribution of the metals does not differ along the samplings, but when compared the results obtained from the water, muscles and shells of the shrimp with the results obtained for the sediments the difference is significant. In sediments and shrimp shells, higher concentrations of heavy metals were observed, independently of the lagoon, mainly aluminum and iron. The concentrations of the essential metals were significant in the muscles of the shrimp caught in the two lagoons. The mean concentrations of iron obtained for the muscles of the shrimp caught in the Imaruí lagoon were 114.91 mg.kg-1, zinc 54.64 mg.kg-1, copper 49.69 mg.kg-1 and manganese 6.99 mg.kg-1. For the Mirim lagoon the results were very similar, where for iron the average concentration was 102.64 mg.kg-1, zinc 57.70 mg.kg-1, copper 45.36 mg.kg-1 and manganese 7, 60 mg.kg-1. However, for non-essential metals, the values observed were less expressive. For Imaruí lagoon the mean concentrations obtained for cadmium were 0.19 mg.kg-1, arsenic 1.55 mg.kg-1, lead 0.89 mg.kg-1 and chromium 2.44 mg.kg-1. For the Mirim lagoon the mean concentrations observed were slightly higher for all the metals analyzed, where the average concentration for cadmium was 0.21 mg.kg-1, arsenic 2.12 mg.kg-1, lead 1.17 mg .kg-1 e chromium 4.11 mg.kg-1. Finally, for both the shrimp caught in the Imaruí lagoon and the Mirim lagoon, concentrations of metals in the muscles below the maximum limits allowed by arsenic, cadmium and mercury legislation were found, except for lead in November 2017, with concentration 1.02 mg.Kg-1 in the Imaruí lagoon and 0.52 mg.Kg-1 in the Mirim lagoon, and the limit established by the legislation is 0.50 mg.Kg-1. Key words: Water quality index, Laguna Estuarine System, heavy metals.