Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2008
Publication Date: 8/1/2008
Citation: He, Z., Ohno, T., Wu, F., Olk, D.C., Honeycutt, C.W., Olanya, O.M. 2008. Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Spectroscopy for Characterization of Humic Substances. Soil Science Society of America Journal. 72:1248-1255. Interpretive Summary: Because organic matter (OM) influences many processes in soils and natural waters, increased knowledge of OM may shed light on its function in nutrient cycling and nutrition. Two advanced instrumental analyses, Capillary Electrophoresis and Fluorescence Spectroscopy, have been used in natural OM studies. However, investigation of OM using the two methods together has not been reported so far. Therefore, in this project, we characterized 13 OM samples obtained from the International Humic Substances Society (IHSS) using the two methods, and analyzed the relationship between the two sets of data. The mutual relevance of data collected from each of the two methods provided novel insight into the correlation of complex OM fluorescence characteristics to specific OM fractions. As the combination of the two methods together provided a novel approach in characterizing OM, application of this approach in soil chemistry will enhance our ability to explore the characteristics of soil OM in relation to different management practices or ecosystems.
Technical Abstract: Capillary electrophoresis (CE) and fluorescence spectroscopy have been used in natural organic matter (NOM) studies. In this study, we characterized five fulvic acids, six humic acids and two unprocessed NOM samples obtained from the International Humic Substances Society (IHSS) using these two analytical methods. The electropherograms of all samples revealed three peak features. The first and third peaks were sharp. The second peak had a broad, hump-shaped feature. The pattern and shapes of these peaks were different among the fulvic acid, humic acid, and unprocessed NOM samples. Excitation-emission matrix (EEM) fluorescence spectroscopic analysis revealed that each of the 13 NOM samples contained four components. However, the relative amounts of the four components varied with sample origin. Autoclaving these samples for 1 hour (heat decomposition) produced additional CE peaks and changed portions of the four fluorophore components, indicating that both methods can be used to investigate the dynamics of NOM decomposition. Although four fluorophore components were present in each of the three CE fractions, their relative abundances varied among the three CE fractions. Specifically, Fraction 1 and 2 were rich in Component 1 and 4, but sparse in Component 2, compared to their original samples. Fraction 2 also contained less Component 3. The distribution of the four components in Fraction 3 was similar to that of the original samples. The mutual relevance of data collected from each of the two methods provided novel insight into the correlation of complex NOM fluorescence spectra to specific NOM fractions.