Kiyoshi Tsutsuki

Chemical studies on soil humic acids: II. Composition of oxygen-containing functional groups of humic acids

The levels of alcoholic and phenolic hydroxyl, methoxyl, carboxyl, and carbonyl groups of 33 to 38 humic acids obtained from various types of soils were determined to analyze the relationships between the amounts of these functional groups and the degree of humification or the types of soils. The amounts of various oxygen-containing functional groups examined were all proven to be significantly different among the various types of humic acids by analyses of variance. During humification. generally, the carboxyl and carbonyl groups increased while alcoholic and phenolic hydroxyl and methoxyl groups decreased. Linear and logarithmic regression analyses of carboxyl group contents on RF values (optical density of the alkaline solution of humic acids at 600 nm) gave very significant positive correlations. The carboxyl group contents of Rp type humic acids and humic acids from calcareous soils were largely distributed in the upper side of the regression curve. The carbonyl group contents showed a very ...

Molecular size distribution of humic acids as affected by the ionic strength and the degree of humification

Molecular size distribution of soil humic acids was investigated by permeation chromatography on porous silica (µBondagel) and porous glass (Controlled Pore Glass, CPG) which enabled rapid analysis. Humic acid molecule was fully expanded at low ionic strength at pH 7.5, but it shrank considerably with increasing ionic strength. This behavior of humic acid molecule was analogous to that of linear polyelectrolyte molecule. Molecular size of humic acids decreased with increasing RF value and carboxyl group content and with decreasing 41og K value (namely with the increasing degree of humification). This phenomenon was attributed to oxidative depolymerization and intramolecular condensation during the process of humification. Based on the fractionation experiments on CPG, the fraction with the highest RF value and the lowest Δlog K value had an intermediate molecular size among the fractions. The excluded large molecular size fraction contained both highly humified components and a large amount of non-colored...

Bomb-carbon, 14C-dating and 13C — Measurements as tracers of organic matter dynamics as well as of morphogenetic and turbation processes

Abstract Organic matter dynamics can be traced by the thermonuclear-bomb-test induced rise of natural C-14, the “bomb-C”, in the whole photosynthesis - nutrition - organic decomposition chain. Layerwise C-14 dated soil profiles from 1965–1980 and past 1980 are evaluated for bomb-C depth penetration. The problem of soil rejuvenation or aging by Bomb-C or fossil fuel-C in conjunction with nutrient pool transfer and enhancement of organic matter production is described. C-dynamics is reflected also by D 14 C and δ 13 C levels in thin layerwise sampled soil profiles of different climates. These measurements can contribute to clarify the C-dynamics in morphogenetic processes, such as our examples of peloturbation and bioturbation.

CHEMICAL STUDIES ON SOIL HUMIC ACIDS : IV. Amino Acid, Phenol, and Sugar Composition in the Acid Hydrolysable Fraction of Humic Acids

The levels of amino acids, phenolic substances, sugars, and total hydrolysable organic matter of 37 humic acids obtained from various types of soils were determined after acid-hydrolysis. The levels of amino acids, hydrolysable phenols and hydrolysable organic matter increased from Rp(2) type to RP(l) type, and decreased with increasing RF values among Rp(l), Po. B, and A type humic acids. Very significant positive linear correlations were found among the levels of these acid hydrolysates. Hexose an duronic acid contents decreased with increasing RF values. The linear correlations between the hexose and uronic acid contents and RF values were very high for calcareous soil humic acids but low for the humic acids from other soils. Amino acids, phenols, and sugars were the main constituents in the acid hydrolysable fraction in humic acids. It was found that absorbance at 210 nm of the acidic supernatant of the hydrolysate was useful for determining the total organic matter content.

CHEMICAL STUDIES ON SOIL HUMIC ACIDS : VII. pH-Dependent Nature of the Ultraviolet and Visible Absorption Spectra of Humic Acids

The pH-dependent nature of the ultraviolet and visible absorption spectra of 39 humic acids (HAs) was investigated. Two kinds of difference absorbance, △E(pH 12.4-7) and JE(pH 7-3.5), were compared...

Degradation and stabilization of humus in buried volcanic ash soils I. Humus composition, molecular size distribution of humic acids, and sugar composition of soils

Changes in the characteristics of the humus of buried volcanic ash soils were investigated in relation to the soil age attaining up to 30,000 YBP. With increasing soil age, the ratios of humin C/total C and Na4P2O7-extractable C/NaOH-extractable C increased. The initial decrease of the ratio of sugar C/total C in the recent layers (<10,000 YBP) was followed by the increase in this ratio in the buried layers older than 10,000 YBP. These phenomena suggested that the humus and polysaccharides of buried volcanic ash soils are stabilized in bound forms with mineral components. The treatment of the Na4P2O7-extracted residue with NaBH4 solubilized the HA exhibiting an intense visible absorption of Pg. The molecular size of HA increased in the recent layers with age, but partially decreased in the buried layers. It is inferred from these results that the decomposition of the easily decomposable organic components and the formation of humic substances took place in the recent layers, while the decomposition of unp...

Characterization of humin-metal complexes in a buried volcanic ash soil profile and a peat soil

Abstract Humin was prepared from samples of a buried humic volcanic ash soil profile and a peat soil by the HF/HCl treatment method as well as by the DMSO extraction method. Recovery of humin carbon was 35-86% by HF/HCl treatment and 9-22% by DMSO extraction. With respect to the elementary composition, DMSO-humin was characterized by higher H/C and N/C ratios and a lower degree of unsaturation compared with HF-humin. The elementary composition of the humin from the peat soil was similar to that of lignin. Both HF-humin and DMSO-humin contained a large amount of ash. In HF-humin, aluminum was the predominant metal accompanied by small amounts of magnesium and calcium. In DMSO-humin, iron was the predominant metal accompanied by a small amount of titanium. Other elements were contained in trace amounts in both humin preparations. Though both HF-humin and DMSO-humin were insoluble in aqueous alkaline solution, a large part of them could be sohibilized in alkaline solution by treatment with Chelex 100, a chel...

13C-NMR investigation of humic and fulvic acids obtained from some typical Japanese soils

Abstract 13 C-NMR spectra of humic acids (HAs), fulvic acids (FAs), and PVP-adsorbed and non-adsorbed fractions of FAs were measured quantitatively. The spectra indicated that more aromatic-C and less carbohydrate-C were contained in the order of HA, PVP-adsorbed fraction of FA, and PVP-non-adsorbed fraction of FA. 13 C-NMR spectra and the composition of carbon species also differed considerably between A-type HA and Rp-type HA obtained from an ando soil and a grey lowland soil, respectively. When compared among different types of soils, PVP-adsorbed as well as non-adsorbed fractions of FAs showed similar spectra and compositions of carbon species. Furthermore, it was suggested that saccharides in FAs were predominantly linked by 1–4 bonds.

CHEMICAL STUDIES ON SOIL HUMIC ACIDS : VI. Absorbance-pH Curves of Humic Acids

The relationship between the ultraviolet and visible absorbance and the pH value of solution of each 3 samples of A, B, and Rp type humic acids and the Pg fraction of a P type humic acid was invest...

Determination of molecular weights of humic acids by osmotic pressure measurement and by permeation chromatography on controlled pore glass

Number-average molecular weights (M n) of humic acids (HAs) were determined by osmometry and by permeation chromatography on controlled pore glass with a pore size of 500 A. M n value of dialyzed HAs tended to decrease in the order of Rp(2)>Rp(l)>P0 type, and increase in the order of P0<B<A type. M n value of non-dialyzed HAs did not show any remarkable difference among the HA types, which was considered to be due to the predominance in the number of species with lower molecular weight (< 10,000) in HAs. M n value calculated from the permeation chromatograms showed a similar trend to that of M n obtained by osmometry, but the values differed depending on the detection methods. Ultraviolet absorption gave a smaller value for M n while the differential refractive index gave a larger value for M n than that by osmometry. It was shown that both the decrease and increase in the molecular weight take place during the humiflcation process of HAs, where the decrease was considered to be associated with the...