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| Registros recuperados: 25 | |
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| CASTRO, V. L. S. S. de; CLEMENTE, Z.; JONSSON, C. M.; SILVA, M. S. G. M. e; VALLIM, J. H.; MEDEIROS, A. M. Z.; MARTINEZ, D. S. T.. |
| O objetivo deste trabalho foi determinar valores de concentração sem efeito previsível (PNEC) para óxido de grafeno (GO), considerando a presença ou ausência de ácido húmico no meio aquático. Para isso, foram realizados testes toxicológicos e determinados os valores de concentração de efeito não observado (CENO) para 9 organismos. A PNEC de GO no compartimento aquático, abaixo da qual os efeitos adversos provavelmente não ocorrerão durante a exposição a longo ou curto prazo, foi estimada em 20 ?g/L (na ausência de ácido húmico) e 5 ?g/L (na presença de ácido húmico). Estes dados contribuem para avaliação de risco da nanotecnologia. ?- The objective of this work was to estimate the predicted no effect concentration (PNEC) for grapheme oxide (GO),... |
| Tipo: Artigo em anais de congresso (ALICE) |
Palavras-chave: PNEC; Nanotoxicologia; Nanomaterial; Ecotoxicologia; Nanotoxicology; Óxido de grafeno; Composto químico; Toxidez; Organismo aquático; Impacto ambiental; Carbono; Graphene oxide; Ecotoxicology; Humic acids; Aquatic organisms; Nanomaterials. |
| Ano: 2017 |
URL: http://www.alice.cnptia.embrapa.br/alice/handle/doc/1085931 |
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| Mvila,Beaufray Gilaime; Pilar-Izquierdo,María Concepción; Busto,María Dolores; Perez-Mateos,Manuel; Ortega,Natividad. |
| ABSTRACT: In this work, barley seed coating with urease and phosphatase, free and immobilized in humic acids, was studied as a tool to enhance the use efficiency of N and P by plants. The seeds were encapsulated in gels of Ca-alginate by a method that allows gelation of the polymer, containing enzymes, from the surface of seeds outward. The coating process did not affect seed germination. A pot experiment with the coated seeds was carried out. The seed coating with free enzymes increased soil ammonium-N (NH4+-N) and inorganic P up to 39 and 54 %, respectively, and up to 62 and 64 %, with the immobilized enzymes, in comparison with control pots. Seed coating improved N (47-137 %) and P (29-61 %) uptake by plants. Moreover, a synergistic response in N and P... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Soil enzymes; Seed encapsulation; Plant nutrients uptake; Humic acids. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162020000601401 |
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| CANELLAS, L.P.; FAÇANHA, A.R.. |
| The aim of this work was to evaluate the humus composition from an Ultisol from Campos dos Goytacazes, RJ, Brazil. Soil samples of four depths (0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m) and its chemical nature were analysed by elemental composition, E4/E6 ratios and Fourier transformed infrared spectroscopy. The bioactivity of these humified substances was evaluated through their action on maize root growth and H+-ATPase activity of root´s microsomes. In topsoil, the content of high condensed alkaline soluble humic substances is greater than that found in the subsuperficial layers. The chemical nature of humic and fulvic acids also varied with the soil depth. The humic acids isolated from the soil samples exhibited higher bioactivity compared with the... |
| Tipo: Artigo em periódico indexado (ALICE) |
Palavras-chave: Fulvic acids; Humic acids; H+-ATPase; Ácidos húmicos; Ácidos fúlvicos. |
| Ano: 2004 |
URL: http://www.alice.cnptia.embrapa.br/handle/doc/110092 |
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| Canellas,Luciano Pasqualoto; Façanha,Arnoldo Rocha. |
| The aim of this work was to evaluate the humus composition from an Ultisol from Campos dos Goytacazes, RJ, Brazil. Soil samples of four depths (0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m) and its chemical nature were analysed by elemental composition, E4/E6 ratios and Fourier transformed infrared spectroscopy. The bioactivity of these humified substances was evaluated through their action on maize root growth and H+-ATPase activity of roots microsomes. In topsoil, the content of high condensed alkaline soluble humic substances is greater than that found in the subsuperficial layers. The chemical nature of humic and fulvic acids also varied with the soil depth. The humic acids isolated from the soil samples exhibited higher bioactivity compared with the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Fulvic acids; Humic acids; H+-ATPase. |
| Ano: 2004 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X2004000300005 |
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| Lima,Claudivan Costa; Mendonça,Eduardo de Sá; Roig,Asunción. |
| The contribution of humic substances of different composts to the synthesis of humin in a tropical soil was evaluated. Increasing doses (0, 13, 26, 52, and 104 Mg ha-1) of five different composts consisting of agroinpowderrial residues were applied to a Red-Yellow Latosol. These composts were chemically characterized and 13C NMR determined and the quantity of the functional alkyl groups of humic acids applied to the soil as compost was estimated. Thirty days after application of the treatments, organic matter samples were collected for fractionation of humic acids (HA), fulvic acids (FA) and humin (HU), from which the ratios HA/FA and (HA + FA)/HU were calculated. The application of the composts based on castor cake resulted in the highest HU levels in the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Humic acids; Fulvic acids; 13C NMR; Alkyl groups; Recalcitrance. |
| Ano: 2010 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832010000400004 |
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| Ksiezopolska,Alicja. |
| The mechanism of the formation of organomineral complexes in soils is very complex and still little known. Examination of the complexes in unaltered form, as isolated from the soil, is very difficult due to the dispersing effect of all extraction agents which break the complexes up, destroying their natural properties. It is much easier to perform most of the tests on preparations of organomineral complexes obtained under laboratory conditions. This paper is concerned with model research on the formation of synthetic complexes of humic acids with minerals: Na-montmorillonite, mica, kaolinite at various pH values (3-7) and in the presence of aluminum ions. The aim of the research was to develop an optimum reaction of suspension for the synthesis of... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Humic acids; Clay minerals; Aluminum oxide; Degree of complex formation. |
| Ano: 2005 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162005000200007 |
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| CLEMENTE, Z.; SILVA, G. H. da; NUNES, M. C. S.; MARTINEZ, D. S. T.; MAURER-MORELLI, C. V.; THOMAZ, A. A.; CASTRO, V. L. S. S. de. |
| Abstract: The presence of natural organic matter such as humic acid (HA) can influence the behavior of graphene oxide (GO) in the aquatic environment. In this study, zebrafish embryos were analyzed after 5 and 7 days of exposure to GO (100 mg L-1) and HA (20 mg L?1) alone or together. The results indicated that, regardless of the presence of HA, larvae exposed to GO for 5 days showed an increase in locomotor activity, reduction in the yolk sac size, and total length and inhibition of AChE activity, but there was no difference in enzyme expression. The statistical analysis indicated that the reductions in total larval length, yolk sac size, and AChE activity in larvae exposed to GO persisted in relation to the control group, but there was a recovery of... |
| Tipo: Artigo em periódico indexado (ALICE) |
Palavras-chave: Óxido de grafeno; Peixe de Água Doce; Matéria Orgânica; Composto Químico; Toxidez; Graphene oxide; Toxicity; Danio rerio; Ecotoxicology; Environmental impact; Aquatic environment; Humic acids; Biomarkers; Behavior change. |
| Ano: 2019 |
URL: http://www.alice.cnptia.embrapa.br/alice/handle/doc/1115452 |
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| Maia, Claudia Maria Branco de Freitas; Fukamachi, Cristiane Regina Budziak; Cambronero, Yorleni Chang; Dedecek, Renato Antônio; Mangrich, Antônio Sálvio; Narimoto, Kelly Mayumi; Milori, Débora M.B.P.; Simões, Marcelo Luiz. |
| The understanding of soil carbon stabilization processes can be very useful in the development of mitigation techniques for CO2 emissions and global warming. The greater the hydrophobicity of soil organic matter the more stabilized soil organic carbon. Therefore, hydrophobicity can be a sensitive index to characterizethe ‘quality’ of soil organic matter. In this context, the present work aimed to characterize the chemical structures of humic acids collected at three different depths in a hydrophobic Entisol (Neossolo) under loblolly plantation. The results of spectroscopic and chemical analyses (UV-Vis, fluorescence, EPR and X-ray diffractometry) indicated that, as soil depth increased, so did the content of conjugated organic structures, aromatic... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Humic acids; Water repellency; Forest soil; Fluorescence; EPR; X-ray. Solos florestais; Repelência à água; RPE; Fluorescência; Raio-X.. |
| Ano: 2010 |
URL: http://pfb.cnpf.embrapa.br/pfb/index.php/pfb/article/view/86 |
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| COA, F.; CLEMENTE, Z.; LOPES, J. R.; RODRIGUES NETO, L. L.; CASTRO, V. L. S. S. de; ALVES, O. L.; BARBIERI, E.; MARTINEZ, D. S. T.. |
| Resumo: Procedimentos de oxidação química são comumente aplicados em nanotubos de carbono a fim de favorecer sua dispersão em meios aquosos e utilização em remediação ambiental. Entretanto, nestes métodos empregam-se ácidos oxidantes (e.g., HNO3, H2SO4), que apresentam custos elevados para produção em larga escala e problemas ambientais. Neste trabalho, nanotubos de carbono foram modificados com ácido húmico, com o objetivo de promover sua estabilidade coloidal e potencializar sua aplicação como material adsorvente de metais (i.e. Cu2+). Realizou-se uma caracterização físico-química integrada do complexo MWCNT-HA, bem como ensaios de toxicidade aguda em embriões de Danio rerio (zebrafish). |
| Tipo: Artigo em anais de congresso (ALICE) |
Palavras-chave: Nanomateriais; Remediação; Ecotoxicidade; Ácido húmico; Nanotubos de carbono; Composto químico; Carbono; Toxidez; Carbon nanotubes; Ecotoxicology; Humic acids. |
| Ano: 2016 |
URL: http://www.alice.cnptia.embrapa.br/handle/doc/1064375 |
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| Andrade,Felipe Vaz; Mendonça,Eduardo de Sá; Silva,Ivo Ribeiro da. |
| Organic acids play an important role in the nutritional conditions of plants. Their relevance is related to their formation dynamics, mineralization rate and adsorption by soil colloids. This study was carried out to evaluate the dynamics of mineralization and adsorption of organic acid (acetic acid - AA, citric acid - CA and humic acid - HA) applied to the soil. Samples of two Oxisols were used: Rhodic Haplustox (LV) and Typic Haplustox (LVA). The mineralization experiment was arranged in a 2 x 3 x 5 factorial design, based on the factors: two soils (LV and LVA) x three organic acid (OA) types (AA, CA and HA) x five OA rates (0, 1, 2, 4, and 8 mmol dm-3). Organic carbon mineralization in samples was measured by the C-CO2 efflux, produced by the microbial... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Citric acid; Humic acids; Sorption; Biodegradation. |
| Ano: 2013 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832013000400015 |
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| Yagi,Renato; Ferreira,Manoel Evaristo; Cruz,Mara Cristina Pessôa da; Barbosa,José Carlos. |
| This work evaluates effects of cattle manure vermicompost in association with liming on soil fertility indexes. The experiment was carried out in greenhouse conditions, in pots containing samples of a Typic Hapludox, medium-textured soil. Five levels of vermicompost (equivalent to 0, 28, 42, 56, and 70 t ha-1, dry weight) and five liming levels (to raise base saturation to 20, 30, 40, 50, and 60%) were combined in a factorial scheme and samples were incubated for 180 days. Samples of the same soil received the equivalent to 70 t ha-1 of the cattle manure used to produce the vermicompost, and the same lime rates. Cattle manure was better than vermicompost to supply K and Mg. Small differences in P supply were observed between the manures. The vermicompost... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Manure; PH; Fulvic acids; Humic acids; Humin. |
| Ano: 2003 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162003000300021 |
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| Canellas,Luciano Pasqualoto; Espindola,José Antonio Azevedo; Rezende,Carlos Eduardo; Camargo,Plínio Barbosa de; Zandonadi,Daniel Basílio; Rumjanek,Victor Marcos; Guerra,José Guilherme Marinho; Teixeira,Marcelo Grandi; Braz-Filho,Raimundo. |
| Using herbaceous legumes in agricultural systems yields great quantities of plant residues, allowing changes in soil organic matter quality and content over the years. This study was conducted on an Ultisol, at Seropédica, RJ, Brazil, to evaluate the effects of different perennial herbaceous legumes on soil organic matter quality. A factorial scheme with three replications was used to evaluate the species: forage groundnut cv. BR-14951 (Arachis pintoi), tropical kudzu (Pueraria phaseoloides), and siratro (Macroptilium atropurpureum). After the first cut, each plot was divided into two subplots; plants were cut and left on the soil surface or cut and removed. Soil samples of a closed area covered by spontaneous vegetation (mainly C3 plants) or by Panicum... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: FTIR; Fluorescence; Humic acids; Humic substances; 13C. |
| Ano: 2004 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162004000100010 |
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| OLIVEIRA, R. I. de; GAMA-RODRIGUES, A. C.; GAMA-RODRIGUES, E. F.; ZAIA, F. C.; PEREIRA, M. G.; FONTANA, A.. |
| Em solos tropicais, a disponibilidade de fósforo (P) pode ser regulada pela decomposição e mineralização da fração lábil de P orgânico (Po), tornando necessários estudos para saber a sua real contribuição no solo. O objetivo deste trabalho foi avaliar o teor de Po total e lábil em horizontes superficiais de diferentes classes de solo e quais as propriedades do solo exercem controle na acumulação dessas frações de P. Foram estudadas amostras de diferentes horizontes diagnósticos superficiais, a saber: H e O hístico; A chernozêmico; e A húmicos, coletados em vários estados do Brasil. Para a determinação das frações totais de P inorgânico (Pi) e orgânico (Po), foi usado o método da extração-sequencial ácido-alcalina, e a fração lábil de P foi determinada pela... |
| Tipo: Artigo em periódico indexado (ALICE) |
Palavras-chave: Hísticos; A chernozêmicos; A húmicos; Disponibilidade de fósforo; Fósforo lábil; Fósforo; Ácido; Humic acids; Phosphorus. |
| Ano: 2014 |
URL: http://www.alice.cnptia.embrapa.br/handle/doc/1001886 |
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| Yagi,Renato; Ferreira,Manoel Evaristo; Cruz,Mara Cristina Pessôa da; Barbosa,José Carlos; Araújo,Luiz Alberto Navarro de. |
| The interdependence between the C and N cycles is reflected by the levels of soil organic matter (SOM). SOM and organic C levels in water soluble (C-WS) humic acids (C-HA), fulvic acids (C-FA), and humin fractions (C-H) were evaluated through the classic chemical fractionation method in samples of a Rhodic Eutrudox from a randomized blocks experimental design, with split-split-plots using five nitrogen sidedressing levels for corn (0; 60; 120; 180; and 240 kg ha-1 N) as the main treatment, two crop sequences (corn-corn and soybean-corn) as the secondary treatment, and two sampling depths (0 to 0.2 and 0.2 to 0.4 m) as a sub-subtreatment. Nitrogen fertilization did not affect SOM levels, but favored the synthesis of substances in the C-HA fraction. There... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Humic acids; Humin; Urea; Corn; Soybean. |
| Ano: 2005 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162005000400011 |
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| Registros recuperados: 25 | |
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