Remediação de latossolo vermelho eutroférrico contaminado com mercúrio
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Data
2019-10-07
Autores
Lavezzo, Letícia Fernanda
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Universidade Estadual Paulista (Unesp)
Resumo
O mercúrio (Hg) é um metal potencialmente tóxico e não essencial para os organismos. Alternativas menos onerosas e ambientalmente corretas como a remediação com uso de plantas e bactérias podem recuperar áreas contaminadas. Por isso, avaliou-se, em ambiente controlado, o potencial de remediação de plantas e bactérias em Latossolo Vermelho eutroférrico (LVef) contaminado com HgCl2 em diferentes doses de Hg2+. Na primeira etapa, 5 kg de LVef foram contaminados com solução de HgCl2, em delineamento inteiramente casualizado com 4 tratamentos: controle positivo (sem Hg2+) e tratamentos com 5 mg kg-1 de Hg, 24 e 36 mg kg-1 de Hg2+, base seca, em 5 repetições e mantidos por 75 dias com plantas Hibiscus cannabinus para avaliar seu efeito remediador. A quantificação do Hg total foi por espectrofotometria de absorção atômica. O tratamento com 24 mg kg-1 de Hg apresentou fitomassa seca da raiz maior que dos demais. De modo geral, LVef foi responsável por reter maior concentração do Hg do que as plantas. O Hg acumulou em maior proporção nas raízes do que na parte aérea, sendo maior o acúmulo com aumento da dose. A planta que recebeu a dose de 36 mg kg-1 Hg acumulou 2,57 mg kg-1 de Hg por planta, diferindo dos demais tratamentos. Concluiu-se que o LVef adsorveu maior concentração de Hg do que as plantas. O H. cannabinus apresentou resistência a diferentes concentrações de Hg no solo e pode ser considerado como planta potencial estabilizadora de Hg2+, pois acumulou maior concentração de Hg nas raízes do que na parte aérea. Na segunda etapa, isolaram-se 180 microrganismos do solo da etapa anterior e apenas 12 sobreviveram, in vitro, a alta concentração de Hg e 5 foram escolhidas devido à facilidade de cultivo e características morfológicas para serem avaliadas como potenciais remediadoras de Hg associadas à planta de milho. Vasos com 2 kg LVef foram contaminados com HgCl2 sólido, em delineamento inteiramente casualizado com 6 tratamentos: controle (Hg e sem bactéria), tratamento 2 (Hg e bactéria 1), tratamento 3 (Hg e bactéria 2), tratamento 4 (Hg e bactéria 3), tratamento 5 (Hg bactéria 4) e tratamento 6 (Hg e bactéria 5) e 4 repetições. Todos os tratamentos receberam a dose de 36 mg kg-1 de Hg2+. A quantificação do Hg total foi por espectrofotometria de absorção atômica e a identificação das bactérias foi realizada por sequenciamento (Sanger). As bactérias foram identificadas como: Bacillus sp., Enterobacter sp. e Staphylococcus sp. A fitomassa seca da raiz e da parte aérea (PA apresentaram homogeneidade entre os tratamentos analisados. O tratamento 2 (com Enterobacter sp.) foi o que translocou maior quantidade de Hg para a PA, acumulando 0,25 mg kg-1 de Hg total por fitomassa de PA. O tratamento 6 (com Bacillus sp.) acumulou maior quantidade de Hg na raiz e na PA, totalizando 6,99 mg kg-1 de Hg total por planta. Concluiu-se que o LVef adsorveu maior concentração de Hg do que as plantas. O milho apresentou resistência à alta concentração de Hg no solo e o pode ser considerado como planta potencial estabilizadora de Hg2+, pois acumulou maior concentração do metal nas raízes do que na parte aérea.
Mercury (Hg) is a potentially toxic metal and not essential for organisms. Less costly and environmentally sound alternatives such as plant and bacterial remediation have been used to recover contaminated areas. Therefore, in a controlled environment, the potential for remediation of plants and bacteria in an Oxisol contaminated with HgCl2 at different doses of Hg2+ was evaluated. In a first experiment, 5 kg of Oxisol were contaminated with HgCl2 solution, in a completely randomized design with 4 treatments: positive control (without Hg2+) and treatments with 5 mg kg-1 Hg, 24 and 36 mg kg-1 Hg2+, dry basis, and 5 repetitions and maintained for 75 days with Hibiscus cannabinus plants to assess its remediation potential. Total Hg quantification was by atomic absorption spectrophotometry. The 24 mg kg-1 Hg treatment presented higher root dry weight than the others. In general, LVef was responsible for retaining higher Hg concentration than plants. Hg accumulated to a greater extent in the roots than in the shoots, with greater accumulation with increasing dose. Plant that received the dose 36 mg kg-1 Hg accumulated 2,57 mg kg-1 Hg per plant, differing from the other treatments. It was concluded that Oxisol adsorbed higher Hg concentration than plants. H. cannabinus showed resistance to different soil Hg concentrations and can be considered as a potential Hg2+ stabilizing plant because it accumulated higher Hg concentration in the roots than in the shoots. In the second experiment, 180 soil microorganisms were isolated from the previous experiment and only 12 survived, in vitro, the high concentration of Hg and 5 were chosen due to the ease of cultivation and morphological characteristics to be evaluated as potential Hg remediation associated with maize plant. Pots with 2 kg of Oxisol were contaminated with solid HgCl2, in a completely randomized design with 6 treatments: control (Hg and no bacteria), treatment 2 (Hg and bacteria 1), treatment 3 (Hg and bacteria 2), treatment 4 (Hg and bacteria 3), treatment 5 (Hg bacteria 4) and treatment 6 (Hg and bacteria 5) and 4 repetitions. All treatments received a dose of 36 mg kg-1 Hg2+. Total Hg was quantified by atomic absorption spectrophotometry and bacterial identification was performed by sequencing (Sanger). The bacteria were identified as Bacillus sp., Enterobacter sp. and Staphylococcus sp. The root and shoot dry weight showed homogeneity between the analyzed treatments. Treatment 2 (with Enterobacter sp.) was the one of translocated the highest amount of Hg in the shoot, with 0,25 mg kg-1 total Hg per shoot phytomass. The treatment 6 (with Bacillus sp.) accumulated higer amount of Hg in the roots and shoots, with 6,99 mg kg-1 of Hg per plant. It was concluded that the Oxisol adsorbed more Hg than the plants. Maize presented resistance to high soil Hg concentration and can be considered as a potential stabilizing plant for Hg2+ because it accumulated higher concentration of the metal in the roots than in the aerial part. It was concluded that the Oxisol adsorbed more Hg than the plants. Maize presented resistance to high soil Hg concentration and can be considered as a potential stabilizing plant for Hg2+ because it accumulated higher concentration of the metal in the roots than in the shoots.
Mercury (Hg) is a potentially toxic metal and not essential for organisms. Less costly and environmentally sound alternatives such as plant and bacterial remediation have been used to recover contaminated areas. Therefore, in a controlled environment, the potential for remediation of plants and bacteria in an Oxisol contaminated with HgCl2 at different doses of Hg2+ was evaluated. In a first experiment, 5 kg of Oxisol were contaminated with HgCl2 solution, in a completely randomized design with 4 treatments: positive control (without Hg2+) and treatments with 5 mg kg-1 Hg, 24 and 36 mg kg-1 Hg2+, dry basis, and 5 repetitions and maintained for 75 days with Hibiscus cannabinus plants to assess its remediation potential. Total Hg quantification was by atomic absorption spectrophotometry. The 24 mg kg-1 Hg treatment presented higher root dry weight than the others. In general, LVef was responsible for retaining higher Hg concentration than plants. Hg accumulated to a greater extent in the roots than in the shoots, with greater accumulation with increasing dose. Plant that received the dose 36 mg kg-1 Hg accumulated 2,57 mg kg-1 Hg per plant, differing from the other treatments. It was concluded that Oxisol adsorbed higher Hg concentration than plants. H. cannabinus showed resistance to different soil Hg concentrations and can be considered as a potential Hg2+ stabilizing plant because it accumulated higher Hg concentration in the roots than in the shoots. In the second experiment, 180 soil microorganisms were isolated from the previous experiment and only 12 survived, in vitro, the high concentration of Hg and 5 were chosen due to the ease of cultivation and morphological characteristics to be evaluated as potential Hg remediation associated with maize plant. Pots with 2 kg of Oxisol were contaminated with solid HgCl2, in a completely randomized design with 6 treatments: control (Hg and no bacteria), treatment 2 (Hg and bacteria 1), treatment 3 (Hg and bacteria 2), treatment 4 (Hg and bacteria 3), treatment 5 (Hg bacteria 4) and treatment 6 (Hg and bacteria 5) and 4 repetitions. All treatments received a dose of 36 mg kg-1 Hg2+. Total Hg was quantified by atomic absorption spectrophotometry and bacterial identification was performed by sequencing (Sanger). The bacteria were identified as Bacillus sp., Enterobacter sp. and Staphylococcus sp. The root and shoot dry weight showed homogeneity between the analyzed treatments. Treatment 2 (with Enterobacter sp.) was the one of translocated the highest amount of Hg in the shoot, with 0,25 mg kg-1 total Hg per shoot phytomass. The treatment 6 (with Bacillus sp.) accumulated higer amount of Hg in the roots and shoots, with 6,99 mg kg-1 of Hg per plant. It was concluded that the Oxisol adsorbed more Hg than the plants. Maize presented resistance to high soil Hg concentration and can be considered as a potential stabilizing plant for Hg2+ because it accumulated higher concentration of the metal in the roots than in the aerial part. It was concluded that the Oxisol adsorbed more Hg than the plants. Maize presented resistance to high soil Hg concentration and can be considered as a potential stabilizing plant for Hg2+ because it accumulated higher concentration of the metal in the roots than in the shoots.
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Palavras-chave
Biorremediação, Fitorremediação, Metal potencialmente tóxico, Bioremediation, Phytoremediation, Potentially toxic metal