Preparative isolation of aquatic humic substances

Thurman, E. Michael; Malcolm, Ronald L.

doi:10.1021/es00086a012

Cited by 1,342 publications

(679 citation statements)

References 15 publications

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“…The atomic ratio parameters of the C/H, C/N and C/O, functional groups (obtained by 13 C nuclear magnetic resonance spectroscopy), concentration of semiquinone-type free radicals (determined by electronic paramagnetic resonance spectroscopy), pH, pluviometric and fluviometric indices, concentrations of mercury were interpreted using HCA and PCA. …”

Section: Methodsmentioning

confidence: 99%

“…The 13 C NMR experiments with cross polarization (CP), magic angle rotation (MAS) and variable amplitude (VA) were carried out in a Varian Spectrometer (model Unity Inova 400). The samples were conditioned in a cylindrical zirconium rotor, being 5 mm in diameter (Doty Supersonic), rotating at 6 KHz in a Doty Supersonic probe for solid samples.…”

Section: Nuclear Magnetic Resonance ( 13 C Nmr)mentioning

confidence: 99%

“…The samples were conditioned in a cylindrical zirconium rotor, being 5 mm in diameter (Doty Supersonic), rotating at 6 KHz in a Doty Supersonic probe for solid samples. The VACP/MAS 13 C NMR spectra were obtained under the following experimental conditions: a resonance frequency of 100 MHz for 13 C, a spectral band of 20 KHz, a proton preparation pulse of 3.8 μs, a contact time of 1 ms, an acquisition time of 12.8 ms and a relax waiting time of 500 ms. As a reference of the chemical shift in the spectra, hexamethilbenzene (HMB) was used.…”

Section: Nuclear Magnetic Resonance ( 13 C Nmr)mentioning

confidence: 99%

“…As for the aquatic humic substances (AHS), the method is based on chromatographic extraction methods. Thurman and Malcolm 13 define AHS as a non-specific amorphic portion constituted of dissolved organic carbon (DOC) at pH 2 and absorbable in a XAD 8 non-ionic resin column having high distribution-coefficient values. The extracted fraction of DOC in a sample depends on the type of resin utilized, and on the quantity of sample and the eluent utilized.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

Section: Nuclear Magnetic Resonance ( 13 C Nmr)mentioning

confidence: 99%

Section: Nuclear Magnetic Resonance ( 13 C Nmr)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…18 The humic substance was obtained from a 100 L water sample via adsorption on macromolecular anionic resin (XAD-8). After acidification (pH 2, with HCl) the non-filtered water sample was passed through at column filled with XAD-8; the humic substances were eluted by a counter-current flow of NaOH 0,1 M. The humic acids were separated from the fulvic acids by precipitation after acidification at pH 1 of the alkaline eluate.…”

Section: Extraction and Separation Of Humic And Fulvic Acidsmentioning

confidence: 99%

Complexation of Cadmium and Copper by Fluvial Humic Matter and Effects on Their Toxicity

et al. 2006

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Summary -The effects of humic acids and fulvic acids isolated from the River Arno (Italy) on the bioavailability and toxicity of cadmium and copper were assessed in relation to changes in their speciation. Measurements of the complexing capacity of solutions containing these organic ligands were carried out by a titration procedure followed by DPASV and toxicity tests were carried out using lysosomes isolated from rat liver. The complexing capacity of the physiological medium containing about 13 mg/L of humic acids, expressed as ligand concentrations, was 0.30 and 0.072 µmol/L for cadmium and copper respectively; the corresponding conditional stability constants were 4.2 x 10 11 and 1.3 x 10 8 (mol/L) -1 . The complexing capacities of the solution containing the same amount of fulvic acids were 0.33 and 0.164 µmol/L for cadmium and copper respectively, the conditional stability constants were 3.2 x 10 11 and 2.4 x 10 7 (mol/L) -1 . The humic acids reduced the toxicity of cadmium by about 5 times: the EC 50 changed from 4.4 to 20.4 µmol/L. The dose effect curve of copper presented a bisigmoid trend and two EC 50 values can be determined: The EC 50(1) in the presence of humic acids changed from 2.0 to 3.1 µmol/L, while the EC 50(2) increased from 22.3 to 45.3 µmol/L. The fulvic acids reduced the cadmium toxicity by about the same amount as humic acids, from 4.4 to 18.6 µmol/L, but they had no effect on copper toxicity. Analysing the chemical speciation of cadmium and copper in the presence of humic components and under toxicity test conditions we can say that the appreciable decrease of EC 50 is not related to changes in their speciation; we can hypothesize that this is due to different processes, as well as to blocking of the lysosomal membrane. On the basis of the shape of the dose-effect curves obtained for cadmium and copper respectively, we can say that the toxic effects of the two metals are different and we can hypothesize that copper could exercise its toxic activity by inhibiting the ATP-driven proton pump and the function of the Clselective channel.

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On-line size-exclusion chromatography/electrospray ionisation mass spectrometry of aquatic humic and fulvic acids

Persson

Alsberg

Kiss

et al. 2000

Rapid Commun. Mass Spectrom.

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Isolated aquatic humic and fulvic acids were analysed with on-line size exclusion chromatography/electrospray ionisation mass spectrometry (SEC/ESI-MS). An eluent composition which enabled electrospray ionisation was identified. The SEC separation improved interpretability of mass spectra and may open up new possibilities for molecular weight determination of humic substances. A linear dose-response relationship over a factor of 20 was obtained and the limit of detection was 50ng/uL for humic and fulvic acids. Spectral changes due to different ionisation conditions (pH and cone voltage) were investigated. A natural water sample from a Swedish lake was analysed. Copyright 2000 John Wiley & Sons, Ltd.

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Preparative isolation of aquatic humic substances

Cited by 1,342 publications

References 15 publications

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

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

Complexation of Cadmium and Copper by Fluvial Humic Matter and Effects on Their Toxicity

On-line size-exclusion chromatography/electrospray ionisation mass spectrometry of aquatic humic and fulvic acids

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