Spectral Characteristics and Molecular Weight Distribution of Humic Acid and Fulvic Acid Derived from Different Composts
Humic substances(HSs)were separated from the chicken manure compost supplemented with Herb Residue(HR),Wheat Straw(WS)and Rice Husk(RH)as additives,respectively.The HSs were subjected to comprehensive characterization on chemical composition and structures.UV-vis spectra analysis show that all compost-derived humic acid(HA)exhibited stronger aromaticity than folvic acid(FA),with HR-HA and RH-HA displaying more pronounced aro-maticity than WS-FA.Regional volume integration of fluorescence excitation-emission matrix spectra indicate that HA con-tained a higher proportion of humic-like substances(Ⅲ+Ⅴ,86%-91%)than FA(56%-64%),while FA comprised a higher percentage of protein-like substances(Ⅰ+Ⅱ,28%-37%)than HA(5%-9%).These findings suggest that HA exhibits a higher humification degree and larger molecular weight.In addition,RH-FA and WS-FA were enriched in hu-mic-like acids and fulvic-like acids,respectively,while HR-FA exhibited abundance in tyrosine-like organic compounds.Fourier transform infrared spectroscopy analysis reveal that FA contained more amide and carboxylic acid structures than HA.In comparison,HR-FA,WS-FA and RH-FA exhibited a higher content of aromatic carboxylic acid,amide and poly-saccharide structures,respectively.Elemental analysis results indicate that HA exhibited a higher C/N ratio and lower O/C ratio than FA,suggesting a higher presence of unsaturated groups in the former and a higher proportion of O-containing groups in the latter.In addition,HSs in WS compost owned a higher aliphatic degree.High performance size exclusion chromatography analysis demonstrates that HA present a broader distribution of high-molecular weight component(＞2×104 Da)than FA.Consequently,HA exhibited 2.7-3.1 and 1.5-1.6 times higher Mw and Mn than FA,respectively.The molecular weight distributions of compost HSs varied with different additives.Notably,the Mn of compost HSs followed the order of HR＞RH＞WS,indicating that HSs in compost with herb residue addition owned the largest molecular weight and humification.In total,the consistent differences in composition and structure were found between HA and FA across different types of organic manure.Moreover,various additives had a significant impact on the composition and structure of same type of manure HSs(i.e.,HA or FA).
composthumic acidfulvic acidspectral characteristicsmolecular weight distribution
万方数据
维普
