Avaliação das atividades desnitrificantes em sedimentos do reservatório do Retiro Baixo, após o rompimento da barragem em Brumadinho – MG

Abstract

The Corrego do Feijao mine, located in Brumadinho-MG, was built to retain tailings from the treatment of iron ore. The rupture of dam I, caused on January 25, 2019, may have caused the contamination of a large part of the Paraopeba river. Since then, physical, chemical and biological parameters and indicators of water quality in the Retiro Baixo reservoir have been monitored. Some microorganisms are sensitive to changes in certain parameters in the environment and can be used as bioindicators in monitoring the environment. Denitrifying bacteria are anaerobic microorganisms that use nitrogen in the nitrate form (NO3 - ) as an electron acceptor in their respiratory cycle, producing nitrite (NO2 - ), which is then converted into gaseous nitrogen (N2), constituting the process of denitrification, part of the nitrogen cycle. This work evaluated the denitrifying activity over time in the Retiro Baixo reservoir, located in Pompeu - MG, about 250km from Brumadinho. During the denitrification tests, the concentrations of nitrate, nitrite and suspended solids, total, fixed and volatile were analyzed for each sample. It was found that there was a decrease in the denitrification rate of the inoculum obtained from the bottom sediment of the Retiro Baixo Reservoir, over the seven campaigns analyzed. Solids of inorganic origin, mainly in campaigns 3, 6 and 7, had a greater influence on the measured results. There was also influence of nitrate and phosphate concentrations, measured in deep water, and the redox potential measured in the bottom sediment. Still, there is the possibility that the increase in mercury concentration observed in campaign 7 may have influenced the increase in the inhibition of the denitrifying community in the inoculum of this campaign.