title: Application of a set of complementary techniques to understand how varying the proportion of two wastes affects humic acids produced by vermicomposting.
abstract: A better understanding of how varying the proportion of different organic wastes affects humic acid (HA) formation during vermicomposting would be useful in producing vermicomposts enriched in HAs. With the aim of improving the knowledge about this issue, a variety of analytical techniques [UV-visible spectroscopic, Fourier transform infrared, fluorescence spectra, solid-state cross-polarization magic-angle spinning (CPMAS) (13)C nuclear magnetic resonance (NMR) spectra, and thermal analysis] was used in the present study to characterize HAs isolated from two mixtures at two different ratios (2:1 and 1:1) of tomato-plant debris (TD) and paper-mill sludge (PS) before and after vermicomposting. The results suggest that vermicomposting increased the HA content in the TD/PS 2:1 and 1:1 mixtures (15.9% and 16.2%, respectively), but the vermicompost produced from the mixture with a higher amount of TD had a greater proportion (24%) of HAs. Both vermicomposting processes caused equal modifications in the humic precursors contained in the different mixtures of TD and PS, and consequently, the HAs in the vermicomposts produced from different waste mixtures exhibited analogous characteristics. Only the set of analytical techniques used in this research was able to detect differences between the HAs isolated from each type of vermicompost. In conclusion, varying the proportion of different wastes may have a stronger influence on the amount of HAs in vermicomposts than on the properties of HAs.
authors.affiliation: Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, 18008 Granada, Spain. Electronic address: manuelj.fernandez@eez.csic.es.
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Fernández-Gómez
authors.affiliation: Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, 18008 Granada, Spain.
authors.forename: Rogelio
authors.initials: R
authors.lastname: Nogales
authors.affiliation: Department of Earth and Environmental Science, University of Pennsylvania, Hayden Hall, 240 S. 33rd Street, Philadelphia, PA 19104, USA.
authors.forename: Alain
authors.initials: A
authors.lastname: Plante
authors.affiliation: Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas, Serrano 115, 28006 Madrid, Spain.
authors.forename: César
authors.initials: C
authors.lastname: Plaza
authors.affiliation: Department of Earth and Environmental Science, University of Pennsylvania, Hayden Hall, 240 S. 33rd Street, Philadelphia, PA 19104, USA; Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas, Serrano 115, 28006 Madrid, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Fernández
mesh_terms: D006812:Humic Substances / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D012987:Soil; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D018505:Waste Management / Q000379:methods*; D014866:Waste Products / Q000032:analysis
chemical_list: D006812:Humic Substances; D012987:Soil; D014866:Waste Products
keywords: Humic acid; Nuclear magnetic resonance; Spectroscopic analysis; Thermal analysis; Vermicomposting; Waste mixture