Fulvic Total acidity

Fulvic acid contains less H, N, and S but more 0 than HA and humin the total acidity and ratio of carboxyl to phenolic hydrohyl groups is almost 3 for FA but near 2 for two other fractions. 

Chemical Shift of Methoxyl Band, ppm Assignments % of Total OCH3 Area of Spectrum Fulvic Humic Acid Acid ... 

Table 1 shows the functional groups in water and soil humic and fulvic fractions. The major functional groups are carboxyl, phenolic hydroxyl, hydroxyl, and carbonyl. The sum of carboxyl and phenolic hydroxyl is total acidity. Total acidity of water fulvic acids is slightly higher compared to soil fulvic acids while total acidity of soil and water hiunic acids is comparable. 

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... 

Figure 6. Dissolution of 5pM Y-FeOOH on photolysis of a) pH 4.0, and b) pH 6.5 solutions containing either 10-1 M citrate, 10 mg/L aquatic fulvic acids, or no added organic agent. Light source simulated solar spectrum of total intensity 300 pEinsteins cm- min-1. (Reproduced from Ref. 32. Copyright 1985, American Chemical Society.)...

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. 

Goodman, B.A. Cheshire, M.V. (1987) Characterization of iron-fulvic acid complexes using Mossbauer and FPR spectroscopy. Sci. Total Fnviron. 62 229-240 Goodman, B.A. Lewis, D.G. (1981) Mossbauer spectra of aluminous goethites (a-FeOOH). J. Soil Sci. 32 351-363 Goodman, B.A. (1988) An introduction to physical and chemical principles. In Studd, J.W. Goodman, B.A. Schwertmann, U. (eds.) Iron in soils and day minerals. D. Reidel Publ. Co., Dordrecht, Holland, NATO ASI Sen 217 19-36... 

The weight of ash-free humic acid was derived from 10 g air-dry soil, therefore should be multiplied by 10 to convert to percent air-dry soil and further converted to percentage oven-dry soil. The fulvic and humic acid content may be expressed as a percentage of total soil organic matter, which is quantified as soil organic carbon (SOC). SOC is conveniently determined from the loss on ignition, where the correlation is ... 

SOM, soil organic matter HS, humic substances DH, degree of humification HAC, humic acid C FAC, fulvic acid C TEC, total extractable C HR, humification rate HI, humification index NHC, nonhumified C TOC, total organic C HA, humic acid FA, fulvic acids UV-Vis, ultraviolet-visible FT-IR, Fourier transform infrared NMR, nuclear magnetic resonance ESR, electron spin resonance EEM, excitation-emission matrix. 

Senesi, N., Miano,T. M., Provenzano, M. R., and Brunetti, G. (1989). Spectroscopic and compositional comparative characterization of IHSS reference and standard fulvic and humic acids of various origin. Sci. Total Environ. 81/82,143-156. 

Turner, D.R., Varney, M.S., Whitfield, M., Mantoura, R.F.C. and Riley, J.P (1987) Electrochemical studies of copper and lead complexation by fulvic acid. II. A critical comparison of potentiometric and polarographic measurements. Sci. Total Environ., 60, 17-34. 

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