Koyo Yonebayashi

Characterization and grouping of aquatic fulvic acids isolated from clear-water rivers and lakes in Japan.

Characteristics of aquatic fulvic acids (FAs) from 10 clear waters in Japan (around the temperate zone) were revealed by several analytical techniques-high performance size exclusion chromatography (HPSEC), elemental analysis, liquid-state (13)C NMR spectroscopy, isotopic analyses (delta(13)C and delta(15)N), and compared with those of International Humic Substances Society (IHSS) standard samples including FAs from brown waters (Suwannee, Pony, and Nordic FAs). Generally clear-water FAs were different from brown-water FAs in chemical properties. Weight-average molecular weights (Mw) of the clear-water FAs were similar to each other, whereas their elemental compositions and carbon species distribution were different. The clear-water FAs all exhibited a high proportion of alkyl carbons, which may be attributed to microbial activity. delta(13)C and delta(15)N values of the FAs indicated that there would be a huge gap between origin and chemical structure of clear-water FA. Results of the chemical structural analyses described above were not always linked to those of the isotopic analyses (delta(13)C and delta(15)N). Multivariate statistical analysis, i.e. cluster and principal component analysis was applied to reveal differences or similarities in a more objective manner. The FAs were always classified into two clear-water groups and one brown-water group. Aryl-C and O-Alkyl-C contents were important for the grouping. We speculate that the grouping might depend on the differences of aquatic microbial activity caused by the differences of residence time of water.

Effects of heating on composition, degree of darkness, and stacking nanostructure of soil humic acids

Wildfires and prescribed burning can affect both the quality and the quantity of organic matter in soils. In this study, we investigated qualitative and quantitative changes of soil humic substances in two different soils (an Entisol from a paddy field and an Inceptisol from a cedar forest) under several controlled heating conditions. Soil samples were heated in a muffle furnace at 200, 250, or 300 °C for 1, 3, 5, or 12h. The humic acid and fulvic acid contents of the soil samples prior to and after heating were determined. The degree of darkness, elemental composition, carbon and nitrogen stable isotope ratios, (13)C nuclear magnetic resonance spectra, and X-ray diffraction patterns of humic acids extracted from the soils before and after heating were measured. The proportion of humic acids in total carbon decreased with increasing heating time at high temperature (300 °C), but increased with increasing heating time at ≤ 250 °C. The degree of darkness of the humic acids increased with increasing heating time and temperature. During darkening, the H/C atomic ratios, the proportion of aromatic C, and the carbon and nitrogen stable isotope ratios increased, whereas the proportions of alkyl C and O-alkyl C decreased. X-ray diffraction analysis verified that a stacking nanostructure developed by heating. Changes in the chemical structure of the humic acids from the heated soils depended on the type of soil. The major structural components of the humic acids from the heated Entisol were aromatic C and carboxylic C, whereas aliphatic C, aromatic C, and carboxylic C structural components were found in the humic acids from the heated Inceptisol. These results suggest that the heat-induced changes in the chemical structure of the humic acids depended on the source plant.

Seasonal characteristics of surface water fulvic acids from Lake Biwa and Lake Tankai in Japan

Seasonal characteristics of surface water fulvic acids (FAs) isolated from Japanese clear-water lakes were investigated. Qualitative changes in Lake Biwa and Lake Tankai FAs were determined and compared. Although the relative molecular weights determined by high-performance size-exclusion chromatography did not change remarkably, the elemental compositions,

Evaluation of stacking nanostructure in soil humic acids by analysis of the 002 band of their X-ray diffraction profiles

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Nitrogen uptake by sago palm (Metroxylon sagu Rottb.) in the early growth stages.

values and 1H- and 13C-NMR spectral properties varied with the season. Both the H/C and N/C ratios for Lake Biwa FAs tended to be higher than those for Lake Tankai FAs, but O/C ratios were lower and decreased from spring to winter. The

Effects of ecological succession on surface mineral horizons in Japanese volcanic ash soil

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