Avaliação da possibilidade de detoxificação e utilização agrícola de lodo de esgoto, após bioestimulação, por meio de diferentes bioensaios
Data
2016-07-29
Autores
Sommaggio, Lais Roberta Deroldo [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
A destinação final dos resíduos sólidos urbanos, como a do lodo de esgoto (LE) é de extrema preocupação, tanto pela sua produção crescente como pela possibilidade de conterem substâncias tóxicas, que podem comprometer o meio ambiente e os organismos expostos a tais resíduos. A reciclagem de LE é uma questão muito importante, sob o ponto de vista ambiental, já que a destinação do mesmo, em sua maioria, é feita em aterros sanitários. O LE, por ser constituído, predominantemente, de matéria orgânica e nutrientes, tem um potencial para uso como recondicionante de solos agrícolas. No entanto, como este resíduo pode apresentar substâncias químicas indesejadas, como metais e substâncias orgânicas tóxicas, além de agentes patogênicos, podendo contaminar os solos. Neste contexto, a bioestimulação utiliza-se da adição de um agente que proporcione uma melhora das propriedades físico-químicas do sistema, para estimular o crescimento de microrganismos autóctones e, consequentemente, melhorar a degradação dos contaminantes. A casca de arroz é um bom agente estimulante porque promove, além de aumento de nutrientes, uma melhora na oxigenação do sistema, atuando como um eficiente descompactante de solo. A espécie Allium cepa e a cultura de células de hepatoma humano (HepG2) podem se caracterizar em interessantes sistemas testes a serem usados em avaliações ecotoxicológicas de compostos biorremediados. Devido à possível aplicação do LE como adubo orgânico, também é fundamental a avaliação do potencial agronômico deste resíduo, para um melhor entendimento do seu comportamento em solos agrícolas. Dessa forma, este trabalho visou avaliar a efetividade da bioestimulação, realizada com a adição de casca de arroz, na descontaminação do LE, por meio de ensaios ecotoxicológicos com A. cepa e células em cultura HepG2. Adicionalmente, foi avaliado o potencial agronômico do composto biorremediado, por análise química e por ensaios com o organismo teste Lactuca sativa. Amostras do LE, puras (LEP) e de suas misturas com solo (LE+S) e solo e casca de arroz (LE+S+CA) foram coletas antes (T0) e após serem biorremediadas por períodos de 3 (T1) e 6 (T2) meses. Os bioensaios com A. cepa e HepG2 foram realizados com os extratos aquosos das amostras. Os resultados obtidos para análise de fertilidade revelam que as amostras que continham os compostos biorremediados, possuíram um aumento do pH, da matéria orgânica e de macro e micronutrientes, quando comparado ao solo controle. As análises biométricas, realizadas com a espécie L. sativa, mostraram aumento significativos do número folhas, para todas as amostras tratadas com os compostos biorremediados, nos tempos T1 e T2. Com relação ao aumento da biomassa de raiz, caule e folhas dessa espécie, houve um aumento significativo das plantas cultivadas com LE+S+CA (T1). Para a biomassa da raiz, houve aumento nas alfaces do tratamento LE+S+CA (T2) e para a biomassa caulinar e foliar, o aumento foi dado no tratamento com LEP (T2). Na área foliar, o aumento foi observado nas alfaces cultivadas com LE+S+CA (T1), e LEP (T2). Os bioensaios realizados com A. cepa mostraram que a amostra de LEP (T1 e T2) inibiu a germinação das sementes, sendo necessária, para a obtenção de radículas, sua diluição em água. Foram observados efeitos citotóxicos, genotóxicos e mutagênicos para as amostras diluídas do LEP (T1 e T2). Para a mutagenicidade em F1, nenhum dos tratamentos foi estatisticamente significativo. No parâmetro de genotoxicidade em HepG2, foram observados valores significativos para o total de MNs em LEP (T2); quantidade de brotos celulares em LEP (T0, T1 e T2) e para a anormalidade composta de MN e broto em LEP (T1 e T2), demonstrando genotoxicidade nas amostras de LEP. Dessa forma, esse estudo demonstrou que embora as amostras biorremediadas de LE apresentaram uma melhora nos parâmetros agronômicos da espécie L.sativa, os extratos aquosos das amostras de LEP apresentaram-se tóxicos aos sistemas testes empregados, mesmo após os períodos de remediação. No entanto, a amostra bioestimulada LE+S+CA não apresentou efeitos tóxicos significativos para nenhum dos bioensaios, indicando a importância do desenvolvimento de tratamentos prévios do LE com agentes descompactantes, como a casca de arroz, para a sua detoxificação e utilização segura em solos agrícolas. Neste trabalho, também foi observada a eficiência dos ensaios realizados com os organismos testes Allium cepa e células HepG2 em avaliar a detoxificação de LE, após o mesmo ser submetidos a processos de biorremediação.
The human solid residues final destination, as sewage sludge (SS), is extremely concerned, both as for its growing production and for the possibility to contain toxic substances, which can compromise the environment and the exposed organisms. The SS recycling is a very important question beneath the environmental point of view, once its destination, most, it is done at sanitary landfills. The SS, for being predominantly constituted by organic matter and nutrients, has the potential to the use as reconditioner of agricultural lands. However, as this residue can present unwanted chemical substances, like metals and toxic organic substances, besides pathogenic agents, it can also contaminate the soil. The biostimulation uses the addition of an agent which provides an improvement on the physical-chemical properties of the system, to stimulate the growth of the autochthonous microorganisms and, consequently, to improve the degradation of contaminants. Rice hull is a good stimulant agent because it can promote, besides an increase of nutrients, an improvement on the system oxygenation, acting then as an efficient soil decompression agent. The Allium cepa specie and human hepatoma cell culture (HepG2) can be characterized in interesting test-organisms to be used in ecotoxicological evaluations of bioremediated compounds. Due to the possibly application of SS as organic fertilizer, is also fundamental the evaluation of the agronomic potential of this residue for a better understanding of its behavior in agricultural soils. In this way, this study aimed to assess the effectivity of biostimulation, performed with the addiction of rice hulls, on the SS decontamination, by ecotoxicological assays with A. cepa and HepG2 cell culture. Additionaly, the agronomic potential of the bioremediated compound was evaluated by chemical analysis and by assays with the test-organism Lactuca sativa. Samples of the SS, pure (SSP) and mixtures with soil (SS+S) and soil with rice hulls (SS+S+RH) were collected before (T0) and after being bioremediated for 3 (T1) and 6 (T2) months period. All bioassays were performed with the aqueous extracts of the samples. The obtained results for the fertility analysis test reveal that the samples, which contained the bioremediated compounds, have an increase on the pH, organic matter and on macro and micronutrients, when compared with the soil control. The biometrical analysis performed with the L. sativa specie show a significant increase on the number of leaves for all the treated samples with the bioremediated compounds, on the T1 and T2 period. With regard to the root, stem and leaves biomass increase of this specie, there was a significant increase of the cultivated plants with SS+S+RH (T1). To the root biomass, there was an increase on the lettuce of the treatment SS+S+RH (T2) and to the stem and leaves biomass, the increase was given on the treatment with SSP (T2). On the leaf area, the increase was observed on the SS+S+RH (T1) and SSP (T2) cultivated lettuces. The bioassays performed with A. cepa show that the SSP (T1 and T2) sample inhibited the seed germination, so it was necessary its dilution in water to obtain the roots. Cytotoxic, genotoxic and mutagenic effects were observed for the diluted SSP (T1 and T2) samples. For the mutagenicity in F1, none of the treatments was statistically significant. For the genotoxicity parameter in HepG2, significant values to the total of MNs in SSP were observed; an amount of nuclear buds in SSP (T0, T1 and T2) and to the abnormality composed by MN and nuclear buds in SSP (T1 and T2) show genotoxicity in SSP samples. Thus, this study showed that, although the SS bioremediated samples showed an improvement on the agronomic parameters of the L. sativa specie, the aqueous extracts of the SSP samples present toxic to the test-systems used, even after the bioremediation period. Though, the SS+S+RH biostimulated sample didn’t show significant toxic effects for any bioassays, indicating the importance of the development of SS previous treatments with decompressing agents, as the rice hulls, to its detoxification and safety utilization in agricultural soils. In this study, the efficacy of the performed bioassays with the test-organisms A. cepa and HepG2 cells was also observed in evaluating the SS detoxification after being submitted to bioremediation processes.
The human solid residues final destination, as sewage sludge (SS), is extremely concerned, both as for its growing production and for the possibility to contain toxic substances, which can compromise the environment and the exposed organisms. The SS recycling is a very important question beneath the environmental point of view, once its destination, most, it is done at sanitary landfills. The SS, for being predominantly constituted by organic matter and nutrients, has the potential to the use as reconditioner of agricultural lands. However, as this residue can present unwanted chemical substances, like metals and toxic organic substances, besides pathogenic agents, it can also contaminate the soil. The biostimulation uses the addition of an agent which provides an improvement on the physical-chemical properties of the system, to stimulate the growth of the autochthonous microorganisms and, consequently, to improve the degradation of contaminants. Rice hull is a good stimulant agent because it can promote, besides an increase of nutrients, an improvement on the system oxygenation, acting then as an efficient soil decompression agent. The Allium cepa specie and human hepatoma cell culture (HepG2) can be characterized in interesting test-organisms to be used in ecotoxicological evaluations of bioremediated compounds. Due to the possibly application of SS as organic fertilizer, is also fundamental the evaluation of the agronomic potential of this residue for a better understanding of its behavior in agricultural soils. In this way, this study aimed to assess the effectivity of biostimulation, performed with the addiction of rice hulls, on the SS decontamination, by ecotoxicological assays with A. cepa and HepG2 cell culture. Additionaly, the agronomic potential of the bioremediated compound was evaluated by chemical analysis and by assays with the test-organism Lactuca sativa. Samples of the SS, pure (SSP) and mixtures with soil (SS+S) and soil with rice hulls (SS+S+RH) were collected before (T0) and after being bioremediated for 3 (T1) and 6 (T2) months period. All bioassays were performed with the aqueous extracts of the samples. The obtained results for the fertility analysis test reveal that the samples, which contained the bioremediated compounds, have an increase on the pH, organic matter and on macro and micronutrients, when compared with the soil control. The biometrical analysis performed with the L. sativa specie show a significant increase on the number of leaves for all the treated samples with the bioremediated compounds, on the T1 and T2 period. With regard to the root, stem and leaves biomass increase of this specie, there was a significant increase of the cultivated plants with SS+S+RH (T1). To the root biomass, there was an increase on the lettuce of the treatment SS+S+RH (T2) and to the stem and leaves biomass, the increase was given on the treatment with SSP (T2). On the leaf area, the increase was observed on the SS+S+RH (T1) and SSP (T2) cultivated lettuces. The bioassays performed with A. cepa show that the SSP (T1 and T2) sample inhibited the seed germination, so it was necessary its dilution in water to obtain the roots. Cytotoxic, genotoxic and mutagenic effects were observed for the diluted SSP (T1 and T2) samples. For the mutagenicity in F1, none of the treatments was statistically significant. For the genotoxicity parameter in HepG2, significant values to the total of MNs in SSP were observed; an amount of nuclear buds in SSP (T0, T1 and T2) and to the abnormality composed by MN and nuclear buds in SSP (T1 and T2) show genotoxicity in SSP samples. Thus, this study showed that, although the SS bioremediated samples showed an improvement on the agronomic parameters of the L. sativa specie, the aqueous extracts of the SSP samples present toxic to the test-systems used, even after the bioremediation period. Though, the SS+S+RH biostimulated sample didn’t show significant toxic effects for any bioassays, indicating the importance of the development of SS previous treatments with decompressing agents, as the rice hulls, to its detoxification and safety utilization in agricultural soils. In this study, the efficacy of the performed bioassays with the test-organisms A. cepa and HepG2 cells was also observed in evaluating the SS detoxification after being submitted to bioremediation processes.
Descrição
Palavras-chave
Ensaios ecotoxicológicos, Allium cepa, Cultura de células de mamífero, Teste do MN, Resíduo sólido, Potencial agronômico, Casca de arroz, Agronomic potential, Ecotoxicological assays, Mammal cell culture, MN test, Rice hulls, Solid residues