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Biblioteca(s): |
Embrapa Instrumentação. |
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Data corrente: |
22/12/1999 |
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Data da última atualização: |
22/12/1999 |
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Autoria: |
SPOSITO, G.; MARTIN-NETO, L.; YANG, A. |
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Afiliação: |
University of California-Ecosystem Sciences Division; EMBRAPA-CNPDIA. |
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Título: |
Atrazine complexation by soil humic acids. |
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Ano de publicação: |
1996 |
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Fonte/Imprenta: |
Journal of Environmental Quality, Madison, v.25, n.6, p.1203-1209, Nov./Dec. 1996. |
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Idioma: |
Inglês |
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Conteúdo: |
Atrazine complexation pathways with soil humic acid remain a controversial issue, in part because of the absence of direct spectroscopic information. Recent optical and magnetic resonance spectral data indicate that proton-transfer and, to a lesser extent, hydrogen bonding are as important as electron-transfer in the mechanisms of reaction between atrazine and humic acid, whereas other s-triazines appear to react more strongly by electron transfer mechanisms. Two representative temperate-zone humic acids were selected to probe the issue of complexation mechanisms more decisively. They were reacted at pH < 7 with 140mmol mE-3 atrazine solution under exclusion of light. Infrared and electron spin resonance spectra of the resulting products gave evidence for proton-transfer and, under certain conditions, electron-transfer reactions. The spectroscopic data were analyzed in terms of the molecular properties of humic acids and s-triazines. The analysis suggested a general guiding principle to characterize the complexation mechanisms of s-triazines with soil humic acids. Proton-transfer is favored (and electron-transfer is disfavored) for humic acids of high acidic functional group content and for s-triazines of low basicity. Electron-transfer mechanisms are favored for humic acids of low acidic functional group content and for s-triazines of high basicity. This principle illustrates the importance of specific molecular structure to understanding reactivity between the s-triazines and humic acids. MenosAtrazine complexation pathways with soil humic acid remain a controversial issue, in part because of the absence of direct spectroscopic information. Recent optical and magnetic resonance spectral data indicate that proton-transfer and, to a lesser extent, hydrogen bonding are as important as electron-transfer in the mechanisms of reaction between atrazine and humic acid, whereas other s-triazines appear to react more strongly by electron transfer mechanisms. Two representative temperate-zone humic acids were selected to probe the issue of complexation mechanisms more decisively. They were reacted at pH < 7 with 140mmol mE-3 atrazine solution under exclusion of light. Infrared and electron spin resonance spectra of the resulting products gave evidence for proton-transfer and, under certain conditions, electron-transfer reactions. The spectroscopic data were analyzed in terms of the molecular properties of humic acids and s-triazines. The analysis suggested a general guiding principle to characterize the complexation mechanisms of s-triazines with soil humic acids. Proton-transfer is favored (and electron-transfer is disfavored) for humic acids of high acidic functional group content and for s-triazines of low basicity. Electron-transfer mechanisms are favored for humic acids of low acidic functional group content and for s-triazines of high basicity. This principle illustrates the importance of specific molecular structure to understanding reactivity between the s-triazines ... Mostrar Tudo |
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Categoria do assunto: |
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Marc: |
LEADER 01920naa a2200145 a 4500
001 1026424
005 1999-12-22
008 1996 bl --- 0-- u #d
100 1 $aSPOSITO, G.
245 $aAtrazine complexation by soil humic acids.
260 $c1996
520 $aAtrazine complexation pathways with soil humic acid remain a controversial issue, in part because of the absence of direct spectroscopic information. Recent optical and magnetic resonance spectral data indicate that proton-transfer and, to a lesser extent, hydrogen bonding are as important as electron-transfer in the mechanisms of reaction between atrazine and humic acid, whereas other s-triazines appear to react more strongly by electron transfer mechanisms. Two representative temperate-zone humic acids were selected to probe the issue of complexation mechanisms more decisively. They were reacted at pH < 7 with 140mmol mE-3 atrazine solution under exclusion of light. Infrared and electron spin resonance spectra of the resulting products gave evidence for proton-transfer and, under certain conditions, electron-transfer reactions. The spectroscopic data were analyzed in terms of the molecular properties of humic acids and s-triazines. The analysis suggested a general guiding principle to characterize the complexation mechanisms of s-triazines with soil humic acids. Proton-transfer is favored (and electron-transfer is disfavored) for humic acids of high acidic functional group content and for s-triazines of low basicity. Electron-transfer mechanisms are favored for humic acids of low acidic functional group content and for s-triazines of high basicity. This principle illustrates the importance of specific molecular structure to understanding reactivity between the s-triazines and humic acids.
700 1 $aMARTIN-NETO, L.
700 1 $aYANG, A.
773 $tJournal of Environmental Quality, Madison$gv.25, n.6, p.1203-1209, Nov./Dec. 1996.
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