Fulvic extraction

In this work a novel five-step leaching scheme for HM has been developed addressing exchangeable, acid soluble (carbonate), easily reducible (bound to Mn oxides), easily oxidizable (bound to humic and fulvic acids), and moderately reducible (bound to amorphous Ee oxides) fractions extractable by 0.05 M Ca(N03), 0.43 M CH3COOH, 0.1 M NH,OH-HCl (non-acidified), 0.1 M K/,03 (pH 11), and 0.1 M (NH4),C,04 (pH 3), respectively. The sequence of extractants was chosen according to recent studies on the selectivity of leachants toward dissolved phases of soils. 

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

Soil extracts are usually very complex. In water samples, humic and fulvic acids make analysis difficult, especially when polar substances are to be determined. Multidimensional chromatography can also make a significant contribution here to this type of analysis. 

NOTE There are various types of organic contaminants that can be present in boiler FW, including trace amounts of pesticides and naturally occurring humic, fulvic, and tannic acids, and solvent-extractable oily matter, such as nonvolatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and the like. 

Metabolites may also play a role in the association of the substrate with humic and fulvic acid components. Two illustrations are given (a) naphth-l-ol, an established fungal metabolite of naphthalene, may play a role in the association of naphthalene with humic material (Burgos et al. 1996) and (b) it has been shown that C-labeled metabolites of [9- C]-anthracene including 2-hydroxyanthracene-3-carboxylate and phthalate were not extractable from soil with acetone or dichloromethane, and required alkaline hydrolysis for their recovery (Richnow et al. 1998). 

Soils Trichoderma viride, extracts of soil humic fulvic acids stim d plant growth nodule mass dec d nodule no. 120... 

Many researchers have attempted to unravel the mystery of the structure of humus. One approach has been to isolate fractions by extracting humus using various extraction procedures. These procedures result in the isolation of three or more fractions humic acid, fulvic acid, and humin. Humic material is isolated from soil by treating it with alkali. The insoluble material remaining after this treatment is called humin. The alkali solution is acidified to a pH of 1.0 and the precipitate is called humic acid, while the soluble... 

Negrin MA, Espino-Mesa M, Hernandez-Moreno JM. Effect of water soil ratio on phosphate release P, aluminium and fulvic acid associations in water extracts from Andisols and Andie soils. Eur. J. Soil Sci. 1996 47 385-393. 

Klenke et al. [5] described a technique for extraction of humic and fulvic acids from stream sediments and outlined methods for their determination. By means of flame atomic absorption spectrometry, the levels of environmentally important heavy metals (cadmium, copper, chromium, cobalt, nickel and lead) in the fulvic and humic acid extracts were compared with those in the original sediment samples. The pattern distribution of the respective metals in the two cases showed very close agreement, suggesting that the combined extract of humic and fulvic acids could be used as an indicator of the level of heavy metal pollution in flowing waters. 

At present, soil derived humic matter and fulvic acids extracted from freshwater are available commercially and are commonly used to test techniques for DOM detection and also used as model compounds for trace metal chelation studies. The results obtained using these model compounds are frequently extrapolated to the natural environment and measurements on "real" samples provide evidence that this DOM is a good model compound. In the past, some investigators also made available organic matter isolated from marine environments using C18 resins. While these compounds come from aquatic sources, this isolation technique is chemically selective and isolates only a small percentage of oceanic DOM. Reference materials are not currently available for these compounds, which inhibits study of the role they play in a variety of oceanographic processes. 

The humates present in soil are polyelectrolytes and bear some similarity to polyacrylic acid and polymethacrylic acid (49, 50). The molecular weight distribution for the humates is considerable fulvic acid fractions of 1,000 daltons have been isolated (51) while humic acid molecular weights obtained by gel chromatography are in the range 17,000 to 100,000 daltons according to the type of soil from which it was extracted (52). However, ultracentrifugation analysis indicates a molecular range of 2,000 to 1,500,000 daltons for humic acids (55). 

A fractionation procedure has been established and widely applied to studies of humic materials [42-44]. The procedure begins with natural OM (i.e., humus) and uses an aqueous basic solution (e.g., 0.1-0.5 mol/1 NaOH and Na2C03) to solubilize a fraction of the OM. The basic extract is then acidified which causes a precipitate to form, i.e., humic acids (HA). The fraction, which remains in solution, is called fulvic acids (FA). Humin is the name given to the insoluble organic fraction that remains after extraction of humic and fulvic acids. At nearneutral pH (pH 5 - 8), which is characteristic of most natural water, the FA are the most water soluble of these three fractions. HA are somewhat less soluble, with their solubility increasing as the pH increases. Humin is insoluble at all pH values. 

Organic matter extracted from earth materials usually is fractionated on the basis of solubility characteristics. The fractions commonly obtained include humic acid (soluble in alkaline solution, insoluble in acidic solution), fulvic acid (soluble in aqueous media at any pH), hymatomelamic acid (alcohol-soluble part of humic acid), and humin (insoluble in alkaline solutions). This operational fractionation is based in part on the classical definition by Aiken et al. (1985). It should be noticed, however, that this fractionation of soil organic matter does not lead to a pure compound each named fraction consists of a very complicated, heterogeneous mixture of organic substances. Hayes and Malcom (2001) emphasize that biomolecules, which are not part of humic substances, also may precipitate at a pH of 1 or 2 with the humic acids. Furthermore, the more polar compounds may precipitate with fulvic acids. 

Soil anomalies present in the raw element data from a variety of extractions are attributed to the effects of metal scavenging onto the surfaces of either Fe oxides or humic/fulvic acids. These metal... 

Data from the Na-pyrophosphate partial extractions and estimates of organic C contained in humic and fulvic acids from spectroscopic determinations show poor reproducibility over time. Analysis of data from re-sampling in September 2007 show significantly lower results over bedrock mineralisation than the original orientation survey conducted in April 2007, although the general pattern appears to be preserved. Re-analysis of the duplicate field samples in the same batch indicates that this variation largely reflects seasonal variations in metal content of the soils, possibly related to rainfall patterns, but also includes a component of laboratory variation between batches. 

Phenolic compounds have also been oxidatively polymerized to humic substances by clay minerals (29) and by the mineral fraction of a latasol (66). After a 10-day equilibration period, montmoril-lonite and illite clay minerals yielded 44 to 47% of the total added phenolic acids as humic substances whereas quartz gave only 9%. Samples of a latasol yielded over 63% of the total amount, from mixtures in varied proportion, of mono-, di- and trihydroxy phenolic compounds as humic substances (66). Extractions of the reaction products yielded humic, fulvic, and humin fractions that resembled soil natural fractions in color, in acid-base solubility, and in infrared absorption spectra. Wang and co-workers (67) further showed that the catalytic polymerization of catechol to humic substances was, enhanced by the presence of A1 oxide and increased with pH in the 5.0 to 7.0 range. Thus the normally very reactive products of Itgnin degradation can be linked into very stable humic acid polymers which will maintain a pool of potentially reactive phytotoxins in the soil. 

Preparation of Fulvic and Humic Acids. Waxes, resins, and other substances soluble in organic solvents were removed by successive extractions with petroleum ether (35-60°), chloroform, and ethyl acetate. These extractions removed of the original material. 

The insoluble material was removed by centrifuging at 5000 rpm for 15 min in a Beckman Model No J-6B centrifuge. This extraction with alkali was repeated twice more and the solutions of sodium salts of acids were collected. Humic acids were precipitated from the combined NaOH solutions by adjusting the pH to 1 with 2N HCl slowly with stirring and the mixture was left overnight. The precipitated humic acids were collected by filtration through Whatman IMM paper and washed with O.IN HCl. The filtrates were extracted three times with ethyl acetate and the extracts dried over sodium sulfate and evaporated, the residue constituting the fulvic acids. Buth fulvic and humic acids (precipitates) were air-dried, and then dried in a vacuum desiccator over phosphorus pentoxide at room temperature. 

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