Fitorremediação de Bário em ambiente alagado : alterações eletroquímicas, redução de barita e dinâmica de absorção e translocação em macrófitas
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Data
2019-02-01
Autores
Ferreira, Amanda Duim
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Universidade Federal do Espírito Santo
Resumo
Macrophytes are plants widely used in the treatment of wastewater and have great
potential for remediation of flooded soils due to their capacity to thrive in anoxic
environments. The radial loss of oxygen is one of the mechanisms that can influence
the redox balance of the soil matrix and of the potential toxicity of elements and
absorption by plants. Many techniques have been proposed to increase the
phytoextraction of metals by macrophytes, however, knowing the timing for the
maximum absorption and translocation is essential for phytoremediation
management. Barium sulfate has a low degree of toxicity, due to the low solubility.
However, under anoxic conditions barium can be reduced to sulphide and be
available to the entire trophic chain, with concerning health and environmental risks.
To evaluate soil-plant interactions during phytoremediation of barium from flooded
soils, two experiments were conducted. In the first experiment, we aimed to assess
the reduction of barium sulfate and the availability of Ba in order to determine the
influence of two species of macrophytes (Thypa domingensis and Eleocharis
acutangula) on the electrochemical changes occurring during soil flooding. We found
that barium sulfate was partially reduced in all treatments. Electrochemical
differences were observed between soils containing T. domingensis and E.
acutangula.The stronger reducing conditions (higher pH and lower Eh) in the soil
vegetated with E. acutangula did not result in a higher accumulation of Ba by this
species. There are many reasons for the higher accumulation of Ba in T.
domingensis than in E. acutangula: a lower proportion between reddish and nonreddish roots, the presence of stolons that can also accumulate Ba and the
electrochemical changes occurring in the soil vegetated by T. domingensis (greater
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oxidation of rhizosphere in vegetated soil, which resulted in lower soil pH and lower
Ba adsorption to iron plaques). In the second experiment we evaluated the
absorption and translocation of Ba over time by E. acutangula, using a soluble
source of barium chloride, in order to simulate that all the barium sulfate had been
reduced. The highest translocation rates were observed after 105 days of cultivation
when the plants reached a state of hyperaccumulation. The maximum barium
accumulation occurred in the aerial parts of the plants at 105 days and in the roots at
120 and 180 days. After 120 days of cultivation, the accumulation in the roots
maintained a high coefficient of removal of Ba from the soil to the plant. At 180 days
the barium available in the soil was depleted due to this high rate of removal by the
roots.
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Palavras-chave
Macrophytes , Macrófitas , Oxi-reduction , Oxirredução , Barite , Sulfato de bário , Accumulation , Acúmulo
Citação
FERREIRA, Amanda Duim. Fitorremediação de Bário em ambiente alagado: alterações eletroquímicas, redução de barita e dinâmica de absorção e translocação em macrófitas. 2019. 58 f. Dissertação (Mestrado em Agricultura Tropical) - Programa de Pós-Graduação em Agricultura Tropical, Universidade Federal do Espírito Santo, São Mateus, 2019.