| |
|
|
| Registros recuperados : 227 | |
| 31. |  | MAIA, C. V. A.; HASSUM, I. C.; VALLADARES, G. S. Parasitoses intestinais em usuários do sus em Limoeiro do Norte, Ceará, antes de expansão de sistema de esgotamento sanitário. Holos, Natal, Ano 31, v. 2, p. 98-109, 2015.| Biblioteca(s): Embrapa Meio-Norte. |
|    |
| Registros recuperados : 227 | |
|
|
|
 | Acesso ao texto completo restrito à biblioteca da Embrapa Florestas. Para informações adicionais entre em contato com cnpf.biblioteca@embrapa.br. |
Registro Completo
|
Biblioteca(s): |
Embrapa Florestas. |
|
Data corrente: |
03/02/2009 |
|
Data da última atualização: |
25/02/2015 |
|
Tipo da produção científica: |
Artigo em Periódico Indexado |
|
Circulação/Nível: |
Internacional - A |
|
Autoria: |
MAIA, C. M. B. F.; PICCOLO, A.; MANGRICH, A. S. |
|
Afiliação: |
Claudia Maria Branco Freitas Maia, Embrapa Florestas; Alessandro Piccolo, Università di Napoli Federico II; Antonio S. Mangrich, UFPR. |
|
Título: |
Molecular size distribution of compost-derived humates as a function of concentration and different counterions. |
|
Ano de publicação: |
2008 |
|
Fonte/Imprenta: |
Chemosphere, v. 73, n. 8, p. 1162-1166, 2008. |
|
DOI: |
10.1016/j.chemosphere.2008.07.069 |
|
Idioma: |
Inglês |
|
Conteúdo: |
Conformational changes in the structures of humic acids (HA) extracted from compost with varying degrees of maturity were monitored by high performance size exclusion chromatography (HPSEC). The molecular size distribution of HA was compared in solutions containing sodium or ammonium counterions at pH 7 and pH 4.5. These findings indicate that the humates’ molecular size depended not only on the nature of the counterions but also on their concentration in the solution. The physicochemical nature of sodium counterions determined smaller molecular sizes than those of the more hydrated ammonium counterions, at low concentrations of humates. Conversely, at higher humate concentrations, the more compact conformation of sodium humates produced larger molecular sizes than those of ammonium humates due to the aggregation of more hydrophobic surfaces in the sodium humates. Composting led to the degradation of labile microbial components with accumulation of hydrophobic constituents. This caused self-association of hydrophobic compounds into humic superstructures of larger molecular size over composting time. At lower pH, changes in conformational stability by the addition of acetic acid to humate solutions were explained by the supramolecular model of humified organic matter. |
|
Palavras-Chave: |
Compost; Composto; Estrutura supramolecular; HPSEC; Molecular size; Substância húmica; Supramolecular structure; Tamanho molecular. |
|
Thesaurus NAL: |
humic substances. |
|
Categoria do assunto: |
-- |
|
Marc: |
LEADER 02099naa a2200265 a 4500
001 1315461
005 2015-02-25
008 2008 bl uuuu u00u1 u #d
024 7 $a10.1016/j.chemosphere.2008.07.069$2DOI
100 1 $aMAIA, C. M. B. F.
245 $aMolecular size distribution of compost-derived humates as a function of concentration and different counterions.$h[electronic resource]
260 $c2008
520 $aConformational changes in the structures of humic acids (HA) extracted from compost with varying degrees of maturity were monitored by high performance size exclusion chromatography (HPSEC). The molecular size distribution of HA was compared in solutions containing sodium or ammonium counterions at pH 7 and pH 4.5. These findings indicate that the humates’ molecular size depended not only on the nature of the counterions but also on their concentration in the solution. The physicochemical nature of sodium counterions determined smaller molecular sizes than those of the more hydrated ammonium counterions, at low concentrations of humates. Conversely, at higher humate concentrations, the more compact conformation of sodium humates produced larger molecular sizes than those of ammonium humates due to the aggregation of more hydrophobic surfaces in the sodium humates. Composting led to the degradation of labile microbial components with accumulation of hydrophobic constituents. This caused self-association of hydrophobic compounds into humic superstructures of larger molecular size over composting time. At lower pH, changes in conformational stability by the addition of acetic acid to humate solutions were explained by the supramolecular model of humified organic matter.
650 $ahumic substances
653 $aCompost
653 $aComposto
653 $aEstrutura supramolecular
653 $aHPSEC
653 $aMolecular size
653 $aSubstância húmica
653 $aSupramolecular structure
653 $aTamanho molecular
700 1 $aPICCOLO, A.
700 1 $aMANGRICH, A. S.
773 $tChemosphere$gv. 73, n. 8, p. 1162-1166, 2008.
Download
Esconder MarcMostrar Marc Completo |
|
Registro original: |
Embrapa Florestas (CNPF) |
|
|
Biblioteca |
ID |
Origem |
Tipo/Formato |
Classificação |
Cutter |
Registro |
Volume |
Status |
Fechar
|
| Nenhum registro encontrado para a expressão de busca informada. |
|
|
