Characterization of humic and fulvic acids extracted with NaOH and NaOH‐Na‐pyrophosphate mixture from soils of arid and subhumid regions 1. analytical characteristics

Tomar, N.K.; Yadav, Rajpaul; Relan, P. S.

doi:10.1080/15324989209381312

Cited by 14 publications

(2 citation statements)

References 11 publications

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“…The FA sample extracted from the Ghentugachhi soil (FA 1 ) had the highest total acidity with the remaining samples arranged sequentially as follows: FA 1 > HA 2 > FA 2 > HA 1 > HA 3 . The range of total acidity of the given humic/fulvic substances agreed, in general, with those reported by Ghosh and Schnitzer (1980), Saha and Sanyal (1988), Tomar et al (1992a), and Datta et al (2001). Table 3 records the experimental B values (B expt. )…”

Section: Resultssupporting

confidence: 85%

Complexation and release isotherm of arsenic in arsenic-humic/fulvic equilibrium study

Mukhopadhyay

Sanyal

2004

Soil Res.

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Soil organic fractions were extracted from 2 surface soils of West Bengal, one of which was arsenic-contaminated, and were fractionated into fulvic and humic acid fractions following standard procedures. These, and one humic acid sample synthesised in the laboratory, were characterised by pH-potentiometric titrations, viscometric measurements, visible spectrophotometry, and surface tension determinations. The results have been correlated with coiling–decoiling behaviour, as well as aliphatic/aromatic balance of these acids. The stability constant (logK) of the complexes formed by these natural humic/fulvic and synthetic humic acids with arsenic in aqueous phase was evaluated by the ion-exchange method. These logK values tend to suggest that the organo-arsenic complexes were quite stable. Further, the logK values displayed an approximately inverse relationship with the viscosity-average molecular weight, excess time needed to attain a stable higher pH during the pH-potentiometric titration, and also the surface excess (in water) of the given humic/fulvic acid samples. These trends were explained in terms of the relative hydrophobic character of the acids, and their resultant tendencies to complex arsenic in the aqueous phase. The release potential of arsenic from the arsenic–humic/fulvic complexes by soluble phophate and nitrate salts was also examined in terms of the appropriate exchange isotherms. In general, phosphate demonstrated a greater degree of exchangeability with arsenic than did nitrate, at both the lower and higher concentrations.

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Section: Resultssupporting

confidence: 85%

Complexation and release isotherm of arsenic in arsenic-humic/fulvic equilibrium study

Mukhopadhyay

Sanyal

2004

Soil Res.

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“…Tomar et al . (1992) showed that the properties of soil humates, and therefore the properties of the humic–enzyme complexes extracted from soil, depended on the soil characteristics, the type of extractant and the conditions of extraction.…”

Section: Discussionmentioning

confidence: 99%

Characterization of β‐d‐glucosidase extracted from soil fractions

Busto

Pérez-Mateos

2000

European J Soil Science

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Summary One way to study the state in which stabilized extracellular enzymes persist and are active in the soil is by extraction from the soil, with subsequent fractionation of enzyme–organomineral complexes and characterization of such complexes. In order to investigate the location and characteristics of soil β‐glucosidase, three soil fractions were obtained both from real (undisturbed) soil aggregates and from structural (dispersed in water and physically disrupted) aggregates using two different granulometric procedures. The β‐glucosidase activity of the fraction was then assayed. When the aggregates were dispersed, more than 73% of activity was in the soil microaggregates with diameters of less than 50 μm (SF50). These aggregates were associated with strongly humified organic matter. Solutions of diluted pyrophosphate at neutral pH liberated active β‐glucosidase from all fractions, although the efficacy of extraction varied according to the type of fraction. The SF50 fraction and aggregates of 2000–100 μm obtained by sieving (SF2000) showed the greatest β‐glucosidase activity (34.5 and 36.0%, respectively). Micro‐ and ultrafiltration of SF50 extracts increased the total β‐glucosidase activity, whereas these procedures, applied to the RF2000 fraction, decreased it. Humus–β‐glucosidase complexes in the SF50 fraction, between 0.45 μm and 105 nominal molecular weight limit ( nmwl) (SF50II) and < 105nmwl (SF50III) showed an optimum pH at 5.4, and in the SF50I fraction (> 0.45 μm) the optimum was 4.0. The stability of β‐glucosidase in the aggregates of the smallest size SF50II and SF50III decreased at acid pHs. The presence of two enzymes (or two forms of the same enzyme) catalysing the same reaction with different values of Michaelis constant and maximum velocity was observed in all but one of the β‐glucosidase complexes extracted and partially purified from the SF50 aggregates.

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The chemical composition of soil organic matter in classical humic compound fractions and in bulk samples — a review

Beyer

1996

J Plant Nutrition & Soil

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In the present paper new findings in soil organic matter (SOM) research were reviewed with regard to non‐aromatic species in order to make evident the recent conception about the chemical nature of humic matter structure. The main purpose of this paper was to unravel the manifold information of SOM investigations in order to characterize the classical humic matter fractions (fulvic acids, humic acids, humins) and bulk soil samples. Such common state‐of‐the‐art information is missing in current SOM literature. In addition we focus on improvements in SOM research due to the application of the new instrumental methods such as NMR and pyrolysis‐MS and its problems of analysis.

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Characterization of humic and fulvic acids extracted with NaOH and NaOH‐Na‐pyrophosphate mixture from soils of arid and subhumid regions 1. analytical characteristics

Cited by 14 publications

References 11 publications

Complexation and release isotherm of arsenic in arsenic-humic/fulvic equilibrium study

Complexation and release isotherm of arsenic in arsenic-humic/fulvic equilibrium study

Characterization of β‐d‐glucosidase extracted from soil fractions

The chemical composition of soil organic matter in classical humic compound fractions and in bulk samples — a review

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