Ecotoxicological Assessment of the Doce River Surface Water After the Fundão Dam Collapse.

On 5 November 2015, the Samarco Fe ore mining operations released approximately 50 million cubic meters of mining waste into the environment, due to a dam collapse. Aiming at understanding the potential effects on the Doce River, different regions of the course of tailings were monitored using acute and chronic ecotoxicological tests with 4 species: Ceriodaphnia dubia, Daphnia similis, Danio rerio, and Vibrio fischeri. The results showed no acute toxicity for water column organisms. However, chronic toxicity was observed with the tests with the microcrustacean C. dubia, mainly related to the physical effects of the passage of flood wave and increased suspended solids, given that toxicity was reduced after filtering the samples. The results showed different magnitudes of impact among the upper, middle, and lower Doce River, with greater impact close to the dam failure area. Integr Environ Assess Manag 2020;16:608-614. © 2020 SETAC.

Em 5 de novembro de 2015, aproximadamente 50 milhões de m3 de resíduos provenientes da barragem de rejeitos das operações de mineração de minério de ferro da Samarco atingiram o meio ambiente decorrente do seu rompimento. Com o objetivo de compreender os potenciais efeitos sobre o rio Doce, o monitoramento foi realizado, através de testes ecotoxicológicos com quatro espécies de diferentes, das regiões atingidas pela pluma de turbidez. Os resultados demonstraram, de modo geral, ausência de ecotoxicidade aguda para organismos de coluna de água. Entretanto, foi evidenciada ecotoxicidade crônica com o microcrustáceo Ceriodaphnia dubia, que esteve relacionada principalmente aos efeitos físicos da passagem da onda de cheia e ao aumento de sólidos em suspensão na coluna d'água. Os resultados mostraram que a magnitude do impacto foi diferente nas três regiões do rio Doce (alta, média e baixa), com maior intensidade na região mais próxima da área do rompimento da barragem. Integr Environ Assess Manag 2020;16:608-614.

Impacts of the Samarco Tailing Dam Collapse on Metals and Arsenic Concentration in Freshwater Fish Muscle from Doce River, Southeastern Brazil.

On November 2015, Samarco tailings dam in Mariana, Minas Gerais, Brazil, collapsed, releasing 62 million tons of tailings that advanced through 668 km of the Doce River and adjacent floodplain. Although the collapse was the worst environmental disaster in Brazil, little is known about its consequences to aquatic biota. Here we evaluate the effects of the tailings mudflow on metal and As concentration in fish and how concentration correlates with water and fish characteristics. We quantified semitotal amounts of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in fish muscle tissue using inductively coupled plasma mass spectrometry (ICP-MS) in 255 individuals (34 species) sampled in unaffected and affected areas along the Doce River basin. Arsenic and Hg were higher in fish from affected sites, likely due to turbulent mixing of previously sedimented material by the giant tailings wave. Silver and Zn concentrations were higher in unaffected sites. Arsenic concentration in Geophagus brasiliensis decreased with increasing fish weight. Copper and Zn decreased with increasing fish weight considering the whole assembly of fish. The tailings mudflow increased water conductivity, and conductivity increased Al concentration in fish, so we expected a larger Al concentration in fishes from affected sites. However, the observed Al concentration in fishes from affected sites was lower than expected by water conductivity. Thus, the tailings mudflow reduced Al uptake or accumulation in fishes. Mercury decreased with increasing water conductivity in both unaffected and affected sites considering all species and in G. brasiliensis alone. Despite the relatively low concentration range of metals and As found in fish, fishes from sites affected by the Fe ore tailings mudflow showed higher As and Hg concentration, compared to fishes from unaffected sites. The higher As and Hg in affected sites require further detailed monitoring to ensure safeguards of human health by fishing activity along the Doce River. Integr Environ Assess Manag 2020;16:622-630. © 2020 SETAC.

Em novembro de 2015, a barragem de rejeitos da Samarco em Mariana, MG, Brasil, rompeu, liberando 62 milhões de toneladas de rejeitos de minério de ferro que avançaram por 668 km do rio Doce e planície adjacente. Embora este tenha sido considerado o pior desastre ambiental do país, pouco se sabe sobre as consequências da liberação do fluxo de lama para a biota aquática. Aqui avaliamos os efeitos do fluxo de lama de rejeitos sobre a bioacumulação de metais e arsênio em várias espécies de peixes coletadas na bacia do rio Doce e como a bioacumulação se correlaciona com as características da água e dos peixes. Quantificamos as quantidades semitotais de Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb e Zn no tecido muscular de peixes usando ICP-MS em um total de 255 indivíduos (representando 34 espécies), amostrados em locais não afetados e afetados ao longo da bacia do rio Doce. As concentrações de As e Hg foram maiores nos peixes dos locais afetados, provavelmente devido à mistura turbulenta de material previamente sedimentado pela onda gigante de rejeitos. As concentrações de Ag e Zn foram maiores nos peixes de locais não afetados. A concentração de As na espécie mais abundante nos locais não afetados e afetados (Geophagus brasiliensis) diminuiu com o aumento do peso dos peixes. A concentração de Cu e Zn diminuiu com o aumento do peso dos peixes, considerando toda a assembleia de espécies. O fluxo de lama de rejeitos aumentou a condutividade da água e a condutividade aumentou a concentração de Al nos peixes, portanto esperávamos uma maior concentração de Al nos peixes de locais afetados. No entanto, a concentração de Al observada nos peixes de locais afetados foi menor do que o esperado pela condutividade da água. Assim, o fluxo de lama de rejeitos reduziu a assimilação ou o acúmulo de Al nos peixes. O mercúrio diminuiu com o aumento da condutividade da água nos locais não afetados e afetados, considerando todas as espécies e também dentro de G. brasiliensis. Apesar da faixa de concentração relativamente baixa de metais nos peixes, os peixes de locais afetados pelo fluxo de lama de rejeitos de minério de ferro apresentaram maior concentração de As e Hg, em comparação com peixes de locais não afetados. A maior concentração de As e Hg nos locais afetados requer um monitoramento mais detalhado para garantir segurança alimentar em relação à atividade pesqueira ao longo do rio Doce. Integr Environ Assess Manag 2020;16:622-630.

Morphological and histopathological changes in seahorse (Hippocampus reidi) gills after exposure to the water-accommodated fraction of diesel oil.

Industrial activities and urbanization are the main sources of pollutants in estuarine environments. Diesel, which is widely used in urban and port activities, is an important source of hydrocarbons in the aquatic environment, and its water-accommodated fraction (WAF) is toxic to the local biota. This study was performed to analyze the effects of diesel oil WAF on fish. Specifically, we characterized the gill morphology of the seahorse Hippocampus reidi and analyzed the histopathological changes in the gills after exposure to 50% diesel oil WAF. Acute (12, 24, 48, and 96 h) and subchronic (168 and 336 h) toxicity tests were performed. Furthermore, a recovery protocol was conducted: after exposure to 50% WAF for 168 h, the fish were transferred and kept in seawater without contaminants for 336 h, for a total experimental period of 504 h. The seahorse branchial apparatus was found to be tufted with short filaments; the apical surfaces of the pavement cells in the filament and lamellar epithelia formed "crests" and had microridges. Mitochondria-rich cells were distributed exclusively in the lamellar epithelium, while mucous cells were distributed in the filament epithelium. All pathologies observed after acute and subchronic exposure featured progressive time-dependent alterations of lamellar structure that might disrupt gill physiological and metabolic functions. During the recovery period, the gill alterations were gradually repaired.

Water-soluble fraction of petroleum induces genotoxicity and morphological effects in fat snook (Centropomus parallelus).

Petroleum hydrocarbons are one of the primary organic chemicals found in water bodies, and the water-soluble fraction of petroleum (WSFP) may be responsible for much of the toxic effects. In the present study, genotoxicity assays and histopathological analysis of the gills were analyzed for two experimental protocols: 1) Juvenile Centropomus parallelus were exposed to different concentrations of WFSP (0%, 25%, 50% and 75%) for 96h; 2) A second fish group was exposed to 50% WFSP for 168h followed by a post-exposure period for 168h in clean water (recovery). The total benzene, toluene, ethyl benzene and xylene (BTEX) and polycyclic aromatic hydrocarbon (PAH) concentrations at time 0 were 254µgL-1 and 4.72µgL-1 in 25%; 552.9µgL-1 and 9.36µgL-1 in 50%; and 842.4µgL-1 and 9.97µgL-1 in 75% WSFP, respectively. Based on the alkaline comet assay, the damage index (DI) values of fish exposed to 25% WSFP for 96h were significantly higher than those in the control group, and in the micronucleus test, the higher damage values were found in fish exposed to 75% WSFP. Furthermore, this last genotoxic test showed recovery after 168h. At all concentrations of WSFP, several histopathological changes were observed, and overall, most of these changes observed in the gills were classified as proliferative changes and represented a protective mechanism against pollutant uptake. Based on the recovery experiment, the damage was also significantly reduced after recovery. Our results showed that short-term exposure to WSFP compounds triggered cellular alterations in C. parallelus, but total recovery did not occur with time. Additionally, the different periods of exposure were not sufficient to induce severe gill damage in C. parallelus. Moreover, this fish demonstrated its usefulness as a sentinel species.