Influence of Land Use on the Structural Feature of Sedimentary Humic Acids in Rivers in Northwest Hokkaido, Japan

Abstract

Colloidal organic matter is an important factor in our understanding of the transport of trace metals by rivers to coastal areas and the characteristics of organic matter in the sediment, including the effect of humic substances on the transport of such metals. The structural features of humic acids (HAs) derived from surface sediments collected from the mouths of four rivers in northwest Hokkaido, Japan, were evaluated from the perspective of land use in their basins. The sediments in two rivers (referred to as NS and SK) were lacking in HAs, but the sediments of the others (referred to as SM and PO) contained relatively high levels of HAs. UV-vis spectroscopic characteristics suggested that the HAs in SM and PO contained components derived from humified materials. The PO and SM basins contain rice paddy fields, and TMAH-py-GC/MS analysis showed that the pyrograms of paddy soil HA had a similar character to those of PO-HA and SM-HA samples. Thus, the differences of the structural features can be attributed to the land use in river basins. The findings indicate that the properties of organic river sediments are heavily influenced by the type of land use in the river basins.

Mechanism of the Elution of Iron from a Slag-Compost Fertilizer for Restoring Seaweed Beds in Coastal Areas—Characteristic Changes of Steelmaking Slag and Humic Acids Derived from the Fertilizer during the Elution Process

“…HAs were extracted from the freeze-dried samples based on the protocols of the International Humic Substances Society (IHSS), details of which are described elsewhere. 11,12,23 The extracted and purified HAs were freeze-dried to obtain powdered samples. The yields of the HAs were calculated from the dryweight of powdered HA divided by that of the initial sample taken for extraction.…”

High-heat Effects on the Physical and Chemical Properties of Soil Organic Matter and Its Water-soluble Components in Japan’s Forests: A Comprehensive Approach Using Multiple Analytical Methods

“…The C, H, and N concentrations in the thermally treated and untreated soil samples were determined using a Micro Corder JM-10 CHN analyzer (J-Science Lab Co. Ltd., Japan) at The TMAH-py-GC/MS technique provides useful information on detailed structural characterization of SOM. [22][23][24] TMAH can be used to cleave ester and ether-linkages via thermochemolysis, with the formation of methyl esters of phenols and carboxylic acids. 25 Therefore, TMAH-py-GC/MS was applied to the soil samples before and after thermal treatment to take the detail information of their structure.…”