Humin nitrogen

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. 

The relationship of humin to kerogen, and the role of these substances as precursors to coal and petroleum are discussed by Hatcher et al. in Chapter 11. Schnitzer discusses the nature of nitrogen in humic substances in the last chapter (Chapter 12) of the geochemistry section. 

As shown in Table 3, the carbon content of fulvic acid is lower than that of humic acid while nitrogen displays the opposite trend. Humin appears to show slightly higher carbon and lower nitrogen contents than humic acid. 

Gas chromatography was used to analyze amino acids in 6N HCl hydrolysates of fulvic acid, humic acid, and humin from lake sediments (Lakes Suwa, Nakanuma, Yunoko, Haruna, Shoji, Motosu, and Biwa) (Yamamoto, 1983). Table 8 gives an example of analytical results of amino acids (Lake Haruna). The total amino acids for the seven-lake sediments accounted for 3-16% of humin, 11-21% of humic acid, and 4-24% of fulvic acid. The percentage of amino nitrogen in the total nitrogen in each fraction was 20-44% for humin, 21-36% for humic acid, and 4-30% for fulvic acid. 

Bourbonniere and Meyers (unpublished) hydrolyzed humic substances from Lake Huron sediments with 5N NaOH at 170°C for 12 hours under a nitrogen atmosphere and found the following organic acids -Ci6 and n-Cig monocarboxylic acids lactic acid, 2-hydroxybutanoic acid, 3,4-dihydroxy-butanoic acid, oxalic acid, and succinic acid. It was proposed that the smaller organic acids were derived from cellulose-related materials. 2-Hy-droxybenzoic acid, 4-hydroxybenzoic acid, 2,5-dihydroxy-3-pentenoic acid, and vanillic acid were also observed. It was believed that 4-hydroxybenzoic acid and vanillic acid originated from lignin and that the ratio of 3,4-dihy-droxybutanoic acid to vanillic acid indicates the proportion of cellulose to lignin. The proportion was in the order of fulvic acid > humic acid > humin. 

A possibility of diagenetic conversion of lipids into humin by polymerization in sediments was claimed by Shioya and Ishiwatari (1983) on the basis of a laboratory heating experiment. Isolated lipids from Lake Haruna sediments were heated in a nitrogen atmosphere at 125-370°C for 1-7 days. A significant amount of lipids (maximum 50% of the initial weight) were poly-... 

Humic acids and humin contain between 2 and 6% nitrogen, while the nitrogen content of fulvic acids ranges from <1 to 3% (Schnitzer, 1976). Nitrogen... 

Table 5 presents data on the distribution of nitrogen in humic acids, fulvic acids, and humin extracted from tropical soils. Especially noteworthy are the relatively high proportions of amino acid nitrogen in all humic fractions, and the unusually high percentages of total nitrogen identified. Humin is especially rich in amino sugars. 

According to this scheme humus coal was similar to the earlier terms humin and ulmin. Humic acid was thought to be tetrabasic with the empirical formula C0OH52O2H (COOH)it, nitrogen being regarded as an impurity. 

Fe = 0.127%, and 0 (by difference) = 32.0%. Thus every molecule contains 416 atoms of nitrogen, 6.0 sulfur atoms, and 1.00 iron atom. On acid hydrolysis an insoluble humin residue of 18.4% appeared, probably deriving from acid carbohydrates in the molecule. 

Amino acid analyses of horse liver catalase have been carried out by Theorell and Akeson (78) and by Bonnichsen (13), who compared these values with those obtained on horse blood catalase. Bonnichsen s results largely confirmed the earlier values of Theorell and Akeson. Furthermore, he analyzed the catalase for glutamic and aspartic acids and cystine. Horse liver catalase, according to Bonnichsen, contains 3.86% histidine, 8.9% arginine, 7.1% lysine, 10.3% glutamic acid, 16.5% aspartic acid, and 1.85% cystine (mean values). The values for the horse blood catalase were, within the limits of error, the same. This applies to the nitrogen distribution on the fractions humin, anodic, neutral, and cathodic nitrogen as well. 

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