Humic extraction

The difference in values of iCD0M for a solute with different types of fractionated humic materials has been explained in terms of the polarity, molecular size, and molecular configuration of the humic materials. It gives a reasonable estimate of the relative enhancing effects among humic extracts. 

Gramss, G., Ziegenhagen, C., and Sorge, S. (1999). Degradation of soil humic extract by wood-and soil-associated fungi, bacteria and commercial enzymes. Microbial Ecol. 37,140-151. 

Fluka-Tridom humic acid Calcasieu River humic extract, Chiou et al. 1987)... 

Aldrich humic acidNa salt, Fluka-Tridon humic acid, Calcasieu River humic extract, Suwannee River water sample, Sopchoppy River water sample, Chiou et al. 1987)... 

One must even be careful in the preparation of humic extracts for NMR studies. Hatcher and Wilson(28) showed that even a small amount of water in fulvic acids can significantly affect the spectral characteristics. This is due to the fact that the added water induces added molecular mobility to the humic substances, especially fulvic acids, and this added mobility affects the spin dynamics in CPMAS spectra, degrading the ability to obtain quantitative C NMR spectra. The effect is most pronounced for carboxyl carbons, presumably because they associate with water more strongly. 

This work was carried out with the support of the Office of Naval Research under Navy Grant N00014-85C-0020. We thank Dr. G.R.Harvey for kindly supplying some of his humic extracts. We also thank Dr. C.H.Langford for making the results of his studies available to us and for his helpful comments on the manuscript. 

BLANC D. 1958. (The effect of humic extracts on the nitrogen metabolism of plants). Comptes rendus de I Academie des sciences, Paris, 247, 1649-1651. 

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