<b>EDTA-induced phytoextraction of lead and barium by brachiaria (<i>B. decumbens</i> cv. Basilisk) in soil contaminated by oil exploration drilling waste

Abstract

ABSTRACT. The phytoextraction of heavy metals using chelating agents has been widely studied for the remediation of contaminated soils. To evaluate the efficiency of EDTA-induced phytoextraction of Ba and Pb using Brachiaria decumbens for the remediation of soil contaminated by oil well drilling and exploration waste, an experiment was conducted by applying a single dose (6 mmol EDTA kg -1 soil) and split doses of EDTA (three applications of 2 mmol EDTA kg -1 soil). The samples were subjected to sequential extractions using the method proposed by Ure et al. (1993) as modified by Rauret et al. (1999).The application of EDTA did not influence the distribution of Ba in various chemical fractions of the soil. The dry matter production did not differ significantly between the treatments and the control, thereby demonstrating the tolerance of plants to the experimental conditions. The absorption of Pb by plants was influenced by the application of EDTA. The application of a single dose of EDTA influenced the absorption of Pb and its translocation to the aerial plant parts. The application of split doses favoured higher accumulation of Pb in roots. Because of its tolerance to heavy metals and EDTA, B. decumbens has the potential to be used in phytostabilisation.Keywords: heavy metals, phytoremediation, chelating compounds.Uso de EDTA na fitoextração induzida de chumbo e bário por braquiária (B. decumbens cv. Basilisk) em solo contaminado por resíduos de perfuração de poços de petróleo RESUMO. A fitoextração de metais pesados usando agentes quelantes tem sido amplamente estudado para a remediação de solos contaminados. Para avaliar a eficiência do EDTA na fitoextração induzida de Ba e Pb, usando Brachiaria decumbens para a remediação de solos contaminados por perfuração poço de petróleo e resíduos de exploração, foi conduzido um experimento, aplicando uma dose única (6 mmol EDTA kg -1 solo) e divisão de doses de EDTA (três aplicações de 2 mmol EDTA kg -1 solo). As amostras foram submetidas a extrações sequenciais com o método proposto por Ure et al. (1993), conforme modificado por Rauret et al. (1999). A aplicação de EDTA não influenciou a distribuição do Ba nas diferentes frações geoquímicas. A produção de matéria seca não diferiu significativamente entre os tratamentos e o controle, demonstrando assim a tolerância das plantas com as condições experimentais. Houve maior absorção de Pb pelas plantas com a aplicação de EDTA. A aplicação de uma dose única de EDTA influenciou a absorção de Pb e sua translocação para a parte aérea das plantas. A aplicação dividida das doses favoreceu maior acúmulo de Pb nas raízes. Devido à sua tolerância para os metais pesados EDTA, B. decumbens tem o potencial para ser utilizado em fitoestabilização.Palavras-chave: metais pesados, fitorremediação, compostos quelantes.

Germination and initial development of Brachiaria brizantha and Brachiaria decumbens on exposure to cadmium, lead and copper

“…MG 5 of B. brizantha (Table 3). The presence Andrade et al (2014) have observed that exposure of B. decumbens to Ba and Pb has not resulted in differences in dry matter weight either. Exposure of brachiaria to trace elements may result in the production of phytochelatins and antioxidant compounds such as ascorbate and tocopherol, which minimizes the toxic effects of trace elements (Santos et al, 2011).…”

“…An indication of tolerance to plant exposure to trace elements is the dry matter weight proportionality between the absence and presence of these contaminants (Andrade et al, 2014;Tolentino et al, 2014). This has been observed in this study for B. decumbens and for cultivar MG 5.…”

Metals Phytoextraction by Cordia africana from Soils Contaminated with Oil Drilling Waste

“…Oil exploration generates wastes from well drilling, and these wastes have polluting potential and are mainly constituted by fragmented rocks mixed with drilling fluid. These pollutants contain hydrocarbons and heavy metals such as iron, manganese, lead, and, especially, barium (Magalhães et al, 2014;Sampaio et al, 2015).…”

Toxicity of Drilling Waste from Oil Wells on Oligochaeta

“…Barium is an element toxic to organisms. However, the barium present in drilling waste takes the form of barium sulfate, which has low solubility and, consequently, low toxicity, as has already been observed in several plants (Lima et al, 2012;Magalhães et al, 2012;Andrade et al, 2014;Sampaio et al, 2015).…”

“…These residues are generated by mixing the fluid, which is an oil-water emulsion with colloidal matter (which may include bentonite, BaSO 4 , and sodium chloride, among other additives), and ground rock (Darley & Gray, 1988). The effects of applying drilling waste on soil have been investigated (Lima et al, 2012;Magalhães et al, 2014b) and have shown that the elements barium, in reducing conditions, and sodium (Freitas et al, 2015) are the most limiting for the growth of several crops, including rice , sunflower (Sampaio et al, 2015), and Brachiaria (Andrade et al, 2014). However, there are few studies that show the effects on soil invertebrates of applying drilling waste.…”