Gray humic acid

Gray humic acid Coagulated in the presence of electrolyte Grauhumin- saure... 

Crenlc acid (Berz Apocrenic acid elius) Brown humic acids Gray humic acids (Springer)... 

FIGURE 8. Distribution of humus forms in grassland and forest soils. FA = fulvic acid GHA = gray humic acid BHA = brown humic acid. Adapted from Stevenson (1982). 

Alfisols, Spodosols, and Ultisols) are characterized by a high content of fulvic acids that of peat and grassland soils (Mollisols) contains high amounts of humic acid. The humic acids of forest soils are mostly of the brown humic acid type those of grassland soils are of the gray humic acid type, as illustrated in Figure 8. 

FIGURE 10.6 IR spectra of a humic acid at different pH values. Inset, detail of the carboxylic band region. (Reprinted from Chemosphere, 59, no. 5, Alvarez-Puebla, R. A. and Garrido, J. J., Effect of pH on the aggregation of a gray humic acid in colloidal and solid states, 659-667. Copyright 2005, with permission from Elsevier.)... 

Figure 5.4. 13C CPMAS TOSS NMR spectra of free and bound fulvic and humic acids extracted from the woodland and stubbed sections of the Broadbalk experiment before and after incubation for about 5 months at 25 °C. Areas in black and gray indicate, respectively, a decrease and an increase of the corresponding signals after incubation. Reprinted from De Nobili, M., Contin, M., Mahieu, N., Randall, E. W., and Brookes, R C. (2008). Assessment of chemical stabilization of organic C in soils from the long-term experiment at Rothamsted (UK). Waste Management 28, 723-733, with permission from Elsevier.

Figure 15.3. Overlaid HSQC spectra of biopolymers on IHSS peat. (A) Biopolymers lignin (gray), amylopectin (red), albumin (blue) and cuticle (green) overlaid on each other. (B) All biopolymers are illustrated in black. (C) IHSS humic acid extract from peat. (D) Biopolymers (black) overlaid on IHSS peat (green). The highlighted areas in 2D are those not well represented by biopolymers in the HA, namely complex carbohydrates and p- ydroxybcnzoatcs from lignin [see Kelleher and Simpson (2006) for more details]. See color insert. Reprinted from Kelleher, B. R, and Simpson, A. J. (2006). Humic substances in soils Are they really chemically distinct Environ. Sci. Technol. 40,4605-4611, with the permission of the American Chemical Society.

Three different compounds make up HSs Humin (defined as insoluble), humic acid (HA, insoluble at a pH of 1) and fulvic acid (FA, soluble at any pH). Other names used to describe HS are ulmic, h5rmatomelanic, gray humic, brown humic, crenic, apocrenic or 5fellow acid (Swift (1985)),... 

Campbell (1965) made an extensive study of the carbon-dating method as applied to the study of problems in soil organic matter investigations and found it to be very satisfactory. The mean residence times of humus ftom the Ap-horizon of 5 Saskatchewan soils ranged from 250 years for a gray-wooded podzolic soil to 1000 years for black chernozemic soils the humus from chernozems from Alberta was even older. The calcium humates and non-hydrolyzable humic acids of the chernozems had an age of 1,400 years, whereas the age of the humic acid hydrolysate was only 25 years. This hydrolysate, which was a small fraction of the total humus, accounted for 80% of the nitrogen released per annum the major portion of the soil humus was found to be inert. In general, the humus of podzolic soils was much more labile than that of chernozems. 

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