Humic substances fulvic acids

Humic substance Fulvic acid Brown Humic" "Black humic"... 

Ogner, G. and Schnitzer, M. (1970b). Humic substances Fulvic acid-diaklyl phthalate complexes and their role in pollution. Science 170, 317-318. 

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. 

Sarkar JM, Bollag J-M (1987) Inhibitory effect of humic and fulvic acids on oxi-doreductases as measured by the coupling of 2,4-dichlorophenol to humic substances. Sci Total Environ 62 367-377... 

Humic and fulvic acids contain various types of phenolic and carboxylic functional (hydrophilic) groups as well as aromatic and aliphatic moieties which import hydro-phobic properties to these substances. Fig. 4.12 gives a schematic idea on the composition of these substances. We refer to the book of Thurman (1985) and Aiken et al. (1985) for a description of the various properties of humic and fulvic acids in soils and waters and the book by Buffle (1988) for the coordinating properties of humus and humic acids. 

On the other hand, one needs to be aware that soluble humic and fulvic acids can form complexes with organic compounds and render these substances more mobile (cf. Davis, 1984). 

Naturally occurring substances compounds leached from the earths crust (calcium, heavy metals) and leachates from soils and sediments (humic and fulvic acids). 

EDR is typically used for demineralization of brackish water, which often contains poorly soluble minerals such as calcium bicarbonate and calcium sulfate, as well as colloids such as humic and fulvic acids and iron hydroxides The periodic reversal of the direction of the electric current avoids scaling and fouling of the membranes by such substances. 

A problem for both humic- and yellow substances is that for these groups of experimentally defined components of different sources, each analysis will be ambiguous in terms of relative composition and molecular weight distribution. Additionally it appears that almost every scientist working in this field has developed his own extraction procedure (Weber and Wilson, 1975 Mantoura and Riley, 1975 a Schnitzer, 1976 Stuermer and Harvey, 1977). Different extraction times and -procedures result in different compositions of the organic constituents (Laane and Kramer, 1984). Soil humic-and fulvic acids, often used for studies on the interaction with trace elements, and those derived from water have certainly not the same composition and contain not the same distribution of functional groups. Therefore, results should be compared with care (Buffle, 1980 Buffle et al., 1984). 

Chemical differences between these fractions of DOM are apparent, but there is considerable compositional overlap as well. Extraction of humic substances or ultrafiltration removes most of the colored DOM from water samples and most of the dissolved lignin (Ertel et al., 1986 Opsahl and Benner, 1998). This is consistent with the observation that many humic and fulvic acids have molecular masses greater than the cutoff (1000 Da) of the membranes used for DOM isolation by ultrafiltration (Thurman, 1985). 

Thermal analysis of humic-mineral complexes has shown there is an overall reduction in the decomposition temperatures of humic acid that has been com-plexed to a mineral surface. Changes in the exothermic peak temperatures of humic substances in the free and complexed state are well-documented for synthetic mineral complexes with humic and fulvic acid (Schnitzer and Kodama, 1972 Tan, 1977 Schnitzer and Ghosh, 1982) as well as for authentic soil complexes. 

Giusquiani, P. L., Gigliotti, G., Businelli, D., and Macchioni, A. (1994). Spectroscopic comparison between humic and fulvic acids from urban waste compost and soil. In Humic Substances in the Global Environment and Implications on Human Health, Senesi, N., and Miano,T. M., eds., Elsevier, Amsterdam, The Netherlands, pp. 1303-1310. 

De Nobili, M., Brookes, P. C., Contin, M., Mahieu, N., and Randall, E. W. (1999). Qualitative and quantitative changes in free and mineral bound humic and fulvic acids in the Broadbalk Classical Experiment at Rothamsted. Humic Substances Environ. 1, 17-21. 

Abbt-Braun, G. (1992). A Spectroscopic characterization of humic substances in the ultraviolet and visible region. B Interpretation of the pyrolysis products of isolated humic and fulvic acid. In Progress in Hydrogeochemistry, Matthess, G., Frimmel, F., Hirsch, P., Schulz, H. D., and Usdowski, H.-E., eds., Springer, Berlin, A pp. 24-36 B pp. 46-51. 

Scheinost, A. C., Kretzschmar, R., Christl, I., and Jacobsen, C. (2001). Carbon group chemistry of humic and fulvic acid A comparison of C-ls NEXAFS and 13C-NMR spectroscopies. In Humic Substances Structures, Models and Functions, Ghabbour, E. A., and Davies, G., eds., Royal Society of Chemistry, Gateshead, UK, pp. 39 47. 

GuctzloffT. F., and Rice, J. A. (1996). Micellar nature of humic substances. Humic and Fulvic Acids Isolation, Structure, and Environmental Roles, Clark, S. B., ed., American Chemical Society, Washington, D.C., p. 18. 

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