Fitorremediação de Bário em ambiente alagado : alterações eletroquímicas, redução de barita e dinâmica de absorção e translocação em macrófitas

• Autor(a) principal: Ferreira, Amanda Duim
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/10819
• topic: Macrophytes; Oxi-reduction; Barite; Accumulation; Macrófitas; Oxirredução; Sulfato de bário; Acúmulo; Agronomia; Bário; Fitorremediação; 63

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 xii 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.