Substâncias húmicas aquáticas: fracionamento molecular e caracterização de rearranjos internos após complexação com íons metálicos

Sargentini, Ézio; Rocha, Júlio César; Rosa, André Henrique; Zara, Luiz Fabrício; Santos, Ademir dos

doi:10.1590/s0100-40422001000300010

Cited by 31 publications

(32 citation statements)

References 20 publications

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“…Diferem de outras classes de compostos naturais devido à sua estrutura química indefinida e gênese complexa 4,5 . O alto teor de grupos funcionais contendo oxigênio na forma de carboxilas, hidroxilas fenólicas e carbonilas 6 conferem às SH papel importante na reatividade e transporte de espécies orgânicas e inorgânicas 3,7 . A alta capacidade complexante das substâncias húmicas aquáti-cas (SHA) pode alterar a biodisponibilidade e os efeitos toxicológicos de metais em sistemas aquáticos [8][9][10] .…”

Section: Introductionunclassified

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

et al. 2002

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100 - <5 kDa) and characterized by several techniques. Molar ratios H/C suggested higher aromaticity for fractions F1 and F6 whereas molar ratios C/N didn´t show any differences regarding the humification degree between the fractions. The UV-Vis absorbance a254/a436 ratio showed higher results for F4 and F5, probably by less condensed features. FTIR studies showed high similarity in the functional groups in the fractions. The highest percentage of traces of Co, Al, Fe, Mn, Cu, Zn and Ni (determined by ICP-AES) was preferably complexed by fractions F3 and F4 with a greater amount of dissolved organic carbon (DOC). In addition, the exchange constants, determined by ultrafiltration method, showed complexes AHS-Fe and AHS-Al with higher stability than complexes AHS-Co in all fractions.]]>

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Section: Introductionunclassified

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

et al. 2002

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“…The samples indicate carbon atoms having more aliphatic characteristics when compared with the data of Leenheer 36 and Ertel et al 37 However, in relation to the data obtained by Sargentini et al, 40 the samples present more aromatic characteristics.…”

Section: Resultsmentioning

confidence: 46%

“…In summary, analyzing the graphs of Figures 3 and 4 The statistical analyses showed that the more humified samples have the greatest mercury content and the phenolic, aromatic and ester groups were predominant in their interaction with mercury. According to Sargentini et al, 40 the metal-OM complex tends to stabilize itself as a function of time where inter and/or intra-molecular rearrangements occur with the transfer of the metal itself to the more internal complexation sites of humic structures. In this way, the results obtained show that the more humified samples having a greater content of the phenolic/aromatic/ester groups have a greater concentration of mercury possibly related to the lixiviation of more humified OM in the soil for the aquatic system.…”

Section: Samplesmentioning

confidence: 99%

The influence of seasonalness on the structural characteristics of aquatic humic substances extracted from Negro River (Amazon State) waters: interactions with Hg(II)

Oliveira¹,

Sargentini²,

Rosa³

et al. 2007

J. Braz. Chem. Soc.

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Neste trabalho, substâncias húmicas foram extraídas de amostras de água coletadas mensalmente na Bacia do Rio Negro-AM para estudar suas propriedades no ambiente amazônico e interações com íons mercúrio, considerando a influência da variação sazonal na sua formação. Os parâmetros razões atômicas C/H, C/N e C/O, grupos funcionais, radicais livres do tipo semiquinona, pH, índices pluviométricos e fluviométricos, concentrações de mercúrio foram interpretados por análise hierárquica de cluster (AHC) e análise de componentes principais (ACP). As análises estatísticas mostraram que, quanto maior o índice pluviométrico e menor o índice fluviométrico maior o grau de humificação das substâncias húmicas aquáticas. A seguinte ordem decrescente do grau de humificação das SHA coletadas mensalmente pode ser estabelecida: Nov/02 a Fev/03 > Mar/02 a Mai/02 > Jun/02 a Out/02. As maiores concentrações de mercúrio foram determinadas nas amostras mais humificadas, sugerindo que devido a rearranjos inter e/ou intramoleculares, quanto maior o grau de humificação maior a afinidade dos íons Hg(II) pelas substâncias húmicas aquáticas.In this work, humic substances were extracted from water samples collected monthly from the Negro River basin in the Amazon state (Brazil) to study their properties in the Amazonian environment and interactions with the mercury ion considering the influence of seasonalness in this formation. The C/H, C/N and C/O atomic ratio parameters, functional groups, concentration of semiquinone-type free radicals, pH, pluviometric and fluviometric indices, and mercury concentrations were interpreted using hierarchical cluster analysis (HCA) and principal component analysis (PCA). The statistical analyses showed that when the pluviometric index was greater and the fluviometric index was smaller, the degree of humification of aquatic substances was greater. The following decreasing order of the degree of humification of the AHS collected monthly was established: Nov/02 to Feb/03 > Mar/02 to May/02 > Jun/02 to Oct/02. The greatest concentrations of mercury were detected in more humidified samples. These results suggest that due to inter and/or intra-molecular rearrangements, the degree of humification of aquatic humic substances is related to its affinity for Hg(II) ions.Keywords: aquatic humic substance, seasonality, Negro River, Amazon, mercury IntroductionFresh water streams have an important function in the global carbon cycle in that they conduct organic matter (OM) of terrestrial origin and transfer it to the oceans. 1 The Amazonian region is home to the most extensive fluvial system which also has greatest liquid mass of the whole earth and it is covered by the largest pluvial tropical forest. According to Bluntschli, 2 the circulation of marine water through the atmospheric compartment above the forest and then from the forest across the fluvial plains again to the sea has a decisive 861 Oliveira et al. Vol. 18, No. 4, 2007 function in the Amazonian ecosystem. According to Sioli, 3 the forest and the regimes...

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“…Nonetheless, there are similarities in the findings of both studies, with evidence for the occurrence of intra/interrearrangements of NOM binding sites, and a homogeneous trend of metal distributions in all size fractions. 9 In order to explore the possible degradation of NOM, the water sample was placed under agitation for 30 days, after which ultrafiltration was performed and the carbon content measured after 1, 15 and 30 days. Table 2 shows the variation of the percentage of carbon, as a function of time, with t0 representing the in natura sample.…”

Section: Resultsmentioning

confidence: 99%

“…Some studies have suggested that recently-complexed metal ions are preferentially linked with easily accessible functional groups in the organic molecules, with reaction time determining structural changes in NOM molecules and variations in the contents of dissolved organic carbon (DOC) and metals in the various molecular size fractions. [7][8][9][10] Information is therefore needed to improve understanding of the dynamics of natural aquatic systems containing elevated DOC contents, and here we use the example of the Serra de Itabaiana National Park watershed (Brazil). This environmentally protected region contains the headwaters of rivers that are important both from the perspective of water supplies for human consumption, and for irrigation projects affecting around 100,000 inhabitants of an arid region of Sergipe State in northeast Brazil.…”

Section: Introductionmentioning

confidence: 99%

Characterization of interactions between natural organic matter and metals by tangential-flow ultrafiltration and ICP OES

Santos¹,

Romão²,

Oliveira³

et al. 2011

J. Braz. Chem. Soc.

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O fracionamento por tamanho molecular da matéria orgânica natural (MON) de amostras de água do Parque Nacional Serra de Itabaiana (Brasil) foi utilizado para caracterização temporal da complexação de íons metálicos. Um sistema de ultrafiltração em cinco estágios foi usado para separar a MON em seis frações (F1: > 100; F2: 100-50; F3: 50-30; F4: 30-10; F5: 10-5; F6: < 5 kDa). A distribuição obtida, inicialmente para amostra in natura, mostrou que metais (Al, Ba, Cr, Cu, Fe, Mn, Ni, Pb e Sr) foram complexados, preferencialmente, pela fração F1, a qual continha maior concentração de carbono orgânico dissolvido (COD). A seguinte ordem decrescente de distribuição de carbono foi obtida: F1 >> F3 > F2 = F4 > F6 > F5. As frações F2 e F5 foram as mais humificadas e F6 a menos humificada. Após 30 dias com adição de elevadas concentrações de metais nas amostras filtradas novas distribuições de COD e metais foram observadas. Maior COD ainda foi encontrado na F1 com teores de carbono decrescendo na seguinte ordem: F1 > F2 > F3 > F4 > F5 > F6. Os metais apresentaram distribuições similares e homogêneas em todas as frações. Valores de log K foram similares para as amostras in natura e para aquelas de 30 dias após a adição dos metais (7,1 e 7,0; 6,6 e 6,9; e 7,2 e 7,0 para Al, Cu e Fe-MON, respectivamente), indicando uma nova condição de equilíbrio na distribuição dos metais após 30 dias. As espécies formadas entre MON e os metais adicionados mostraram um modelo de distribuição que mudou em função do tempo de complexação, indicando uma transformação dos sítios de ligação da MON, sugerindo que o efeito coletivo das frações é mais importante que as propriedades individuais e confirmando que as frações mais humificadas exercem grande influência na complexação de metais em ambientes aquáticos.Molecular size fractionation of the natural organic matter (NOM) in water samples from the Serra de Itabaiana National Park (Brazil) was used to characterize the temporal behavior of metal ion complexation. A special five-stage tangential-flow ultrafiltration device was used to separate NOM in six size fractions (F1: > 100; F2: 100-50; F3: 50-30; F4: 30-10; F5: 10-5; F6: < 5 kDa). The distribution patterns obtained for one in natura sample showed that metals (Al, Ba, Cr, Cu, Fe, Mn, Ni, Pb and Sr) were preferentially complexed by the F1 fraction, which contained higher concentration of dissolved organic carbon (DOC). The following decreasing order of carbon distribution in the different fractions was obtained: F1 >> F3 > F2 = F4 > F6 > F5. Fractions F2 and F5 were the most humified, and F6 the least. New distributions of DOC and metals were observed after 30 days when high concentrations of metals were added to filtered samples. Highest DOC was still found in F1, with carbon contents decreasing in the following order: F1 > F2 > F3 > F4 > F5 > F6. The studied metals presented similar and homogeneous distributions in all fractions. Values of log K were similar for samples in natura and 30 days after addition of metals (7.1 and 7.0, 6.6 and 6.9, ...

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Substâncias húmicas aquáticas: fracionamento molecular e caracterização de rearranjos internos após complexação com íons metálicos

Cited by 31 publications

References 20 publications

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

The influence of seasonalness on the structural characteristics of aquatic humic substances extracted from Negro River (Amazon State) waters: interactions with Hg(II)

Characterization of interactions between natural organic matter and metals by tangential-flow ultrafiltration and ICP OES

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