Perfil da ictiofauna e níveis de mercúrio em peixes capturados na região do baixo rio São Francisco

Abstract

Mercury contamination has increased its importance in research, due to the risks to organisms, and requires accurate knowledge about the impacts on the environment and health. The objective of the present study was to investigate Hg contamination in muscle tissues of fish captured in the Lower São Francisco region, with the aim of using them as bioindicators. To capture the specimens, a set of gillnets was used, with meshes of 3 to 16 cm between opposite nodes. Two collections were carried out, dry season and rainy season, where about 1,606 specimens were captured in the Lower São Francisco, belonging to a group of 25 species of fish with different eating habits, 13 omnivores, 6 carnivores, 4 detritivores, 1 herbivore and 1 1 plankton, to determine Hg concentrations in muscle tissue, evaluating the influence of trophic position, seasonality and biometrics. The analysis method used to determine the total mercury concentration in the samples was based on thermal decomposition, amalgamation and detection by atomic absorption spectrometry, using the DMA-80 equipment (Direct Mercury Analyzer, Milestone), with direct mercury analysis. To certify the analytical method, analyzes were carried out on the reference material composed of fish protein (DORM-4), with known mercury content (0.410 ± 0.055 mg kg-1), where the agreement was 98.2 ± 2, 4%. The results obtained showed that in the dry period the species Acestrorhynchus lacustris with a carnivorous feeding habit presented the highest average concentration of mercury in the muscle, with a concentration of 0.1183 ± 0.0737 mg kg-1. However, in the rainy season, the species Bryconops affinis with an omnivorous feeding habit was the one that presented the highest levels, with a concentration of 0.1541 ± 0.1053 mg kg-1. Considering the mean concentrations, all species studied in both periods had mercury levels below the maximum limit of 0.5 mg kg-1 in non-predatory fish and 1.0 mg kg-1 in predatory fish, established by the National Agency of Sanitary Surveillance - ANVISA. It was possible to verify that the specimens evaluated both in the dry and in the rainy season had a Risk Quotient lower than 1, not presenting a risk of contamination by Hg capable of causing damage to human health. It should be noted that, even without presenting risks, it should be considered that riverside communities consume fish more frequently, requiring the integration of public power with academia, so that such analyzes in fish are monitored with greater assiduity.