A comparative study of proton and alkaline earth metal binding by humic substances

Lead, Jamie R.; Hamilton−Taylor, John; Hesketh, N.; Jones, Malcolm N.; Wilkinson, A. E.; Tipping, Edward

doi:10.1016/0003-2670(94)80316-1

Cited by 51 publications

(37 citation statements)

References 10 publications

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“…However, care must be taken not to drastically change the nature of the samples. The present work showed no evidence that changes in the sample structure or aggregation had taken place, but Redwood et al 29 demonstrated that material such as humic substances, the major organic constituents of soils and aquatic environments, 36,37 tend to aggregate when subjected to dehydration. Fig.…”

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confidence: 57%

Visualisation of natural aquatic colloids and particles ? a comparison of conventional high vacuum and environmental scanning electron microscopy

Doucet

Lead

Maguire

et al. 2005

J. Environ. Monitor.

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The applicability of environmental scanning electron microscopy (ESEM; imaging of hydrated samples) and conventional high vacuum scanning electron microscopy (SEM; imaging of dried samples at high vacuum) for the observation of natural aquatic colloids and particles was explored and compared. Specific attention was given to the advantages and limitations of these two techniques when used to assess the sizes and morphologies of complex and heterogeneous environmental systems. The observation of specimens using SEM involved drying and coating, whereas ESEM permitted their examination in hydrated form without prior sample preparation or conductive coating. The two techniques provided significantly different micrographs of the same sample. SEM provided sharper images, lower resolution limits (10 nm or lower), but more densely packed particles, suggesting aggregation, and different morphological features than ESEM, suggesting artefacts due to drying. ESEM produced less easily visualised materials, more complex interpretation, slightly higher resolution limits (30-50 nm), but these limitations were more than compensated for by the fact that ESEM samples retained, at least to some extent, their morphological integrity. The results in this paper show that SEM and ESEM should be regarded as complementary techniques for the study of aquatic colloids and particles and that ESEM should be more widely applied to aquatic environmental systems than hitherto.

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contrasting

confidence: 57%

Visualisation of natural aquatic colloids and particles ? a comparison of conventional high vacuum and environmental scanning electron microscopy

Doucet

Lead

Maguire

et al. 2005

J. Environ. Monitor.

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“…This extract, supplied by J. Lead, had been previously well characterized, and the molecular weight of 16 500 determined by ultra centrifugation [23]. The 4 L of well-stirred solution were maintained at a known temperature in the range 15-22 °C.…”

Section: Principles Of Measurementmentioning

confidence: 99%

In situ speciation measurements. Using diffusive gradients in thin films (DGT) to determine inorganically and organically complexed metals

Zhang

Davison

2001

Pure and Applied Chemistry

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The possibilities of using diffusive gradients in thin films (DGT) and anodic stripping voltammetry (ASV) to perform speciation measurements in natural waters are discussed. Both techniques measure labile species, but different approaches have been used to discriminate organic (C org ) and inorganic (C inorg ) metal complexes. In DGT, metals are bound to a resin after passing through a hydrogel that serves as a well-defined diffusion layer. DGT devices with different hydrogels that impede the diffusion of humic substances by different amounts were deployed in solutions of copper and humic substances. Devices with a gel composition that greatly restricted the diffusion of humic substances, but only retarded the diffusion of Cu ions slightly, could be used directly to determine C inorg . By using different, more open pored gels, which allowed some passage of humic substances, it was possible to determine both C org and C inorg . The two separate measurements of C inorg obtained using the two DGT approaches agreed well. At the high concentrations of Cu used there was good agreement with the predicted distribution from the speciation code WHAM. At the lowest Cu concentration, the proportion of C inorg estimated using DGT was higher than with WHAM. Possibilities of errors in the DGT or modeling approaches are discussed.

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“…Aldrich humic acid (AHA) is extracted from peat and was supplied as granules. Aquatic DOM was extracted by lyophilization from 27 liters of GF/F filtered humic rich stream water collected in winter from Whitray Beck, North Yorkshire, U.K. (Lead et al 1994). Frequently, aquatic HS is operationally defined as material that adheres to XAD-8 resin (Thurman 1985).…”

Section: Isolation Of Humic Substances and Preparation For Use-mentioning

confidence: 99%

“…For elemental ratios, the relative standard deviation between replicates was less than 5%. was considered that this molecular size range encompassed the majority of molecular size distributions encountered in humic substances (Thurman et al 1982;De Nobili et al 1989;Lead et al 1994). The eluant used for all experimental runs was degassed CM.…”

Section: Isolation Of Humic Substances and Preparation For Use-mentioning

confidence: 99%

“…The eluate was measured for ultraviolet absorbance using a Pharmacia optical unit LKB UV1 with 280-nm filters. In order to relate size exclusion chromatography (SEC) output to actual molecular weight, the column was calibrated using HS standards of known molecular weight (Lead et al 1994). The results of SEC analysis of the HS are presented as weight-averaged molecular weights (WAMw; Shaw unpubl.…”

Section: Isolation Of Humic Substances and Preparation For Use-mentioning

confidence: 99%

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Further evidence of elemental composition as an indicator of the bioavailability of humic substances to bacteria

Hunt

Parry

Hamilton−Taylor

2000

Limnology & Oceanography

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Batch culture experiments examined the ability of an isolated bacterial community to utilize four humic substances with similar molecular size but variable elemental composition. Univariate and multivariate linear regression analysis of the results provided evidence of a significant positive relationship between the N:C ratio and bacterial concentrations. In contrast, neither H:C nor O:C ratios were significant predictors of humic substances bioavailability, and their inclusion in the multivariate model provided no further explanatory power compared with the univariate model using N:C as the single independent variable. These findings suggest that N:C ratios provide the best indicator of bioavailability for complex, recalcitrant carbon moieties typical of many aquatic systems.

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A comparative study of proton and alkaline earth metal binding by humic substances

Cited by 51 publications

References 10 publications

Visualisation of natural aquatic colloids and particles ? a comparison of conventional high vacuum and environmental scanning electron microscopy

Visualisation of natural aquatic colloids and particles ? a comparison of conventional high vacuum and environmental scanning electron microscopy

In situ speciation measurements. Using diffusive gradients in thin films (DGT) to determine inorganically and organically complexed metals

Further evidence of elemental composition as an indicator of the bioavailability of humic substances to bacteria

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