Pedosphere 15(1): 1--8, 2005
ISSN 1002-0160/CN 32-1315/P
©2005 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Extraction and characterization of humic acids and humin fractions from a black soil of China |
XING Bao-Shan1,2 , LIU Ju-Dong1, LIU Xiao-Bing1,2 and HAN Xiao-Zeng1 |
1 Northeast Institute of Geography and Agro-ecology, Chinese Academy of Sciences, Harbin 150040 (China). Email: bx@pssci.umass.edu;
2 Department of Plant, Soil and Insect Sciences, University of Massachusetts, MA 01003 (USA) |
| ABSTRACT |
| Twenty-three progressive extractions were performed to study individual humic acids (HAs) and humin fractions from a typical black soil (Mollisol) in Heilongjiang Province, China using elemental analysis and spectroscopic techniques. After 23 HA extractions the residue was separated into high and low organic carbon humin fractions. HA yield was the highest for the first extraction and then gradually decreased with further extractions. Organic carbon (OC) of the humin fractions accounted for 58% of total OC even after 23 successive HA extractions. In addition, the atomic C/H ratio decreased during the course of extraction while C/O increased; the E4/E6 ratio from the UV analysis decreased with further extraction while E2/E3 increased; the band assigned to aliphatic carbon (2930 cm-1) in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra gradually increased with progressive extraction; the calculated ratio of the sum of aromatic carbon peak heights to that of aliphatic carbon peak heights from DRIFTS spectra declined with extractions; and nuclear magnetic resonance (NMR) data suggested that HA aliphatic carbons increased with extractions while aromatic carbons decreased. Thus, hydrophobicity and aliphaticity of HAs increased with extractions while polarity and aromaticity decreased. These data showed substantial chemical, structural, and molecular differences among the 23 HAs and two humin fractions. Therefore, these results may help explain why soil and sediment humin fractions have high sorption capacity for organic contaminants. |
| Key Words: elemental composition, humic acid, humin, soil organic matter, spectroscopic analysis |
| Citation: Xing, B. S., Liu, J. D., Liu, X. B. and Han, X. Z. 2005. Extraction and characterization of humic acids and humin fractions from a black soil of China. Pedosphere. 15(1): 1-8. |
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