Effect of lead in the aerobic decomposition of Myriophyllum aquaticum (Vellozo) Verdecourt
Lead is a toxic element that has been used since early times and is still employed today in several industrial processes. Events as the collapse of the Fundão dam in Bento Rodrigues, district of Mariana (MG) on November 2015, significantly increase concentrations of metals above-recommended levels, including lead. In this context, this study aims to evaluate the impact of lead in the cycling rate of organic matter in the aquatic environment. Thus, the rates of aerobic decomposition of Myriophyllum aquaticum (Vell.) Verdec at different concentrations of lead (5.0, 10.0, 20.0 and 30.0 mg L-1) were measured, analyzing the dissolved oxygen consumption. Decomposition chambers filled with samples of water and M. aquaticum were incubated at 20° C in the dark for 80 days and periodically had the oxygen concentrations determined by polarography, when the concentrations were less than 2 mg L-1, the incubations were re-aerated. At the lowest concentrations (5.0 and 10.0 mg L-1) of lead the mineralization was lower, however, the reaction coefficients and the amount of oxygen consumed were equivalent to the control. At the highest concentrations (20.0 and 30.0 mg L-1) the mineralization was increased, with the reduction of reaction coefficients and higher oxygen consumption.
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