Humin fraction

Soil microorganisms degrade methoprene rapidly and extensively (27). The hydroxy ester was isolated as a minor metabolite over 50% of the applied dose was evolved as 1 C02. Radioactivity from [5-1 0]methoprene incorporated into the humic acid, fulvic acid, and humin fractions of soil. 

The chemical structures of the amino acids found in soil-solids are shown in Fig. 6 [25] while the quantities of amino acids found in HS extracted from various solid phases are represented in Fig. 7 (data were collected from Ghosh and Schnitzer [37] and Schnitzer et al. [38]). High levels of amino acid nitrogen were found in HA, FA, and humin fractions, indicating incorporation of common acidic and some neutral amino acids, particularly glycine, alanine, and valine. 

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. 

Chiou, C. T., D. E. Kile, D. W. Rutherford, G. Shung, and S. A. Boyd, Sorption of selected organic compounds from water to a peat soil and its humic-acid and humin fractions Potential sources of the sorption nonlinearity , Environ. Sci. Technol., 34,1254-1258 (2000). 

Banerjee, S. K. (1979). Humin fraction of soil humus. J. Indian Chem. Soc. 56,1094-1097. Baron, M. H., Revault, M., Servagent-Noinville, S., Abadie, J., and Quiquampoix, H. (1999). Chymotrypsin adsorption on montmorillonite Enzymatic activity and kinetic FTIR structural analysis. I. Coll. Interface Sci. 214, 319-332. 

Gouveia, S. E. M., Pessenda, L. C. R., and Aravena, R. (1999). Dating of the humin fraction of soil organic matter and its comparison with 14C ages of fossil charcoal, QJIM Nova 22, 810-814. 

Besides applications with whole soils, LIF can be applied to study physical and insoluble chemical fractions of soil. Gonzalez-Perez et al. (2006b) carried out studies about fractions of SOM under sewage sludge application. In this work, the high fluorescence contribution of humin fraction to the fluorescence of whole soils was... 

Humic and flilvic acids are traditionally extracted from soils and sediment samples as the sodium salts by using sodium hydroxide solution. The material that remains contains the insoluble humin fraction (Figure 3). The alkaline supernatant is acidified to pH 2 with HCl. The humic acid precipitates and the fulvic acid remains in solution with other small molecules such as simple sugars and amino acids. These molecules can be separated by passing the solution through a hydrophobic resin, such as the methacrylate cross-linked polymer, XAD-8. The fulvic acids will sorb to the resin while the more hydrophilic molecules pass through the column. The fulvic acid can be removed with dilute base. 

Polysaccharides are present in fulvic acid, humic acid, and humin fractions of soil organic matter. Extractants remove only a small percentage of the total present and hence determinations must be made by means of hydrolysis followed by analysis of the products. These include hexoses, pentoses and uronic acid. There seems to be no doubt that soil polysaccharides are important constituents of soil organic matter. They have a role in... 

Insight into the nature of NOM as a sorbent of organic compounds can be obtained by examining sorption on derivative materials. We have studied sorption on humic acid particles, as well as on the resulting insoluble humin fraction left after extraction (11). 

Humic substances are high-molecular-mass, polyelectrolytic macromolecules. Molecular masses range from a few hundred for fulvic acid to tens of thousands for the humic acid and humin fractions. 

---