Characteristics of Humic Acids Extracted with Acidified DMSO Solvent and Alkali Solution from Soils of Jilin, China

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  • 中国吉林省の土壌のDMSO抽出腐植酸とアルカリ抽出腐植酸の特徴
  • 中国吉林省の土壌のDMSO油出腐植酸とアルカリ油出腐植酸の特徴
  • チュウゴク キツリンショウ ノ ドジョウ ノ DMSOユシュツフショクサン ト アルカリユシュツフショクサン ノ トクチョウ

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Abstract

Humic substances (HS) were extracted from 5 soils of Jilin province, northeast China, and brown forest soils of Japan using acidified dimethyl-sulfoxide (DMSO) solvent. Humic acid (HA) was separated from the HS and analyzed on E_<600> (absorbance coefficient of 1% HA solution at 600nm), elemental and functional groups composition, component distribution separated with XAD-8 resin, and hexose, pentose, amino acids, and lignin contents. DMSO extractable HS from Jilin soils were 74〜85% of alkaline extractable HS. Black soils showed highest rate of extraction of HS with DMSO, and Solonetz showed lowest one. The HA extracted with DMSO were ca. 85% of those extracted with alkali solution. In case of brown forest soils, DMSO extractable HS and HA were ca. 50% of alkaline extractable HS and HA. DMSO extractable HA showed high values of E_<600>, high contents of carbon, carboxyl and carbonyl groups, and carboxylic component, and low contents of hydrogen, alcoholic hydroxyl group, and aliphatic component. These characteristics were remarkable on Solonetz and brown forest soils but not marked on Black soils. Protonated sulphoxide in acidified DMSO solvent could form strong associations with carboxyl groups in the HS by hydrogen bonding, which would promote solvation. Hence, part of the HS containing high amount of carboxylic groups would selectively extracted with acidified DMSO. From atomic H/C versus O/C diagram and functional groups composition on DMSO extractable and alkaline extractable HA, most of the HA of Black soils would be highly subject to dehydration and carboxylation. Major part of the HA of Lessive and Chernozem would be subject to demethanation, and only the part, which showed high value of E_<600>, could be introduced many carboxyl groups. In case of Solonetz and brown forest soils, demethanation and carboxylation would not take place in most of the HA. Carbohydrates, amino acids, and lignin contents in DMSO extractable HA were lower than those of alkaline extractable HA. Part of polysaccharides and amino compounds were soluble in neutralized DMSO solvent, hence, these compounds would be separated from the HS which was insoluble in the neutralized DMSO. Acidified DMSO extraction procedure provides acceptable and efficient preparation of the HS which is less contaminated with non-humic substances.

Journal

  • Pedologist

    Pedologist 43 (2), 98-107, 1999-12-31

    Japanese Society of Pedology

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