Pb-phytoextraction by maize in a Pb-EDTA treated Oxisol

Abstract

One of the most viable strategies to restore metal contaminated soils is the introduction of plants specialized in their accumulation or able to tolerate very high metal concentrations. This research evaluated: i. the maize as a Pb-accumulator plant; ii. the effects of EDTA-chelating agent for Pb-uptake by maize; iii. amending effect of EDTA on the soil Pb-availability using different extracts. ) and without EDTA. Lead concentrations were determined in maize plant shoots. Soil available Pb was obtained using DTPA, Mehlich-3 and saturation solutions methods. Ionic speciation in the soil solution was performed using the software Visual-Minteq. Although a low t value was found (t <0.70), Pb concentration were high (>1,500 mg kg -1 of Pb) in maize shoots regardless of EDTA addition. Maize plants treated with EDTA had lower dry matter yield, mainly due to toxic levels of Fe and Al of the Oxisol. All extracting solutions were effective to determine available Pb in soil samples, but the saturation extract is a more difficult and time consuming procedure. At low and medium Pb levels, the plants grew less on EDTA, therefore the phytoextration process was less efficient. The addition of EDTA to the soil is not recommended with the purpose of increasing Pb absorption by maize plants. ) e sem EDTA. A concentração de Pb foi determinada na parte aérea das plantas de milho, e no solo determinou-se o Pb disponível pelos métodos DTPA, Mehlich-3 e pasta de saturação. A especiação iônica da solução do solo foi determinada utilizando-se o software Visual-Minteq. Embora tenha sido encontrado um baixo valor t (t <0.70), a concentração de Pb na parte aérea do milho foi alta (>1.500 mg kg -1 ), independente da adição de EDTA. As plantas de milho que receberam EDTA apresentaram redução na massa seca, principalmente devido aos níveis tóxicos de Fe e Al do Latossolo. Todas as soluções extratoras utilizadas foram eficientes em determinar o Pb disponível nas amostras de solo, mas a pasta de saturação foi o processo mais trabalhoso. Em baixa e média concentração de Pb no solo as plantas cresceram menos com EDTA, portanto a fitoextração foi menos eficiente. Não é recomendada a adição de EDTA no solo buscando aumentar a absorção de Pb pelas plantas de milho. Palavras-chave: Mehlich-3, DTPA, fitorremediação, Pb disponível, especiação iônica

EDTA assisted phytorremediation of a Pb contamined soil: metal leaching and uptake by jack beans

“…On the other hand, in the split EDTA application (0.25 + 0.25 g kg -1 ), lower Pb-EDTA complex might be formed since the soil used is rich in Fe and Al and these elements strongly compete with Pb and are preferentially bound by EDTA. This hypothesis is corroborated by Pereira et al(2007) that observed an increase Fe concentration in the soil solution when 0.5 g kg -1 EDTA was applied to a Pbcontaminate soil At the end of the experiment jack bean shoots from EDTA treatments, irrespective of the EDTA application form, presented higher Pb concentrations and accumulation values up to 460 mg kg -1 (Figure 2). Similar results were reported for maize and common bean plants grown in Pb contaminated soil treated with 5 mmol kg -1 of EDTA (Luo et al, 2005).…”

“…aokawa) plants (0.1) and turnip (0.30) (Santos, 2005). Higher F values (0.6) were obtained for maize plants grown in Oxisol samples treated with 2400 mg kg -1 de Pb (with and without EDTA) although for jack bean plants grown with increasing Pb rates (100 -400 μmol L -1 ) in the nutrient solution did not observe significant differences for F values (average 0.04) among treatments (Pereira et al, 2007;Romeiro, 2006).…”

Phytoremediation of lead by jack beans on a Rhodic Hapludox amended with EDTA

“…This fact should also be taken into account for the evaluation of the phytoextraction potential of plants. For instance, jack beans showed about three-fold higher shoot dry matter yields with mean values of 28.1 and 18.4 g per pot compared to 10.0 and 2.3 g per pot for maize under same growth conditions without and with EDTA, respectively (Pereira et al, 2007).…”

Vegetable species for phytoextraction of boron, copper, lead, manganese and zinc from contaminated soil

“…Among the few studies available in Brazil, many have been restricted to academics (Carneiro et al, 2001;Coscione and Berton, 2009;Gabos et al, 2009;Marques et al, 2000;Pereira et al, 2007;Romeiro et al, 2006;Santos et al, 2007;Zeittouni et al, 2007). In spite of that, promising species well known in Brazilian agriculture due to its robustness, good climate adaptation, deep root system and good biomass production have not been evaluated.…”