Por favor, use este identificador para citar o enlazar a este item:
http://hdl.handle.net/10261/174008
COMPARTIR / EXPORTAR:
SHARE CORE BASE | |
Visualizar otros formatos: MARC | Dublin Core | RDF | ORE | MODS | METS | DIDL | DATACITE | |
Título: | Selective effects of forest fires on the structural domains of soil humic acids as shown by dipolar dephasing 13C NMR and graphical-statistical analysis of pyrolysis compounds |
Autor: | Almendros Martín, Gonzalo CSIC ORCID ; Tinoco, Pilar CSIC ORCID; Rosa Arranz, José M. de la; Knicker, Heike CSIC ORCID ; González Pérez, José Antonio ; González-Vila, Francisco Javier CSIC ORCID | Palabras clave: | Humic substance Nuclear magnetic resonance Curie-point pyrolysis Dipolar dephasing Forest fires damage levels Humic acid structural changes NMR |
Fecha de publicación: | abr-2018 | Editor: | Springer Nature | Citación: | Journal of Soils and Sediments 18(4): 1303–1313 (2018) | Resumen: | Purpose: Data management strategies of pyrolysis results and NMR acquisition modes were examined in humic acids (HAs) from control soils and fire-affected soils. The information supplied by dipolar dephasing (DD) 13C NMR spectroscopy and Curie-point pyrolysis were used to assess chemical structures hardly recognizable and measurable, or of unclear interpretation, when using 13C NMR under standard acquisition pulses (cross-polarization/magic angle spinning, CPMAS). Materials and methods: The HAs were isolated from two forest soils under Pinus halepensis and Pinus sylvestris in control and burned sites affected by medium or severe-intensity wildfires. For NMR analyses, during DD acquisition conditions, a 180° 13C pulse was inserted to minimize phase shifts. Curie-Point pyrolysis was carried out at 510 °C for 5 s, and the pyrolysis fragments were analyzed by GC/MS. The total abundances of the major pyrolysis products were compared by an update of the classical Van Krevelen’s graphical-statistical approach, i.e., as surface density values in the space defined by the compound-specific H/C and O/C atomic ratios. Results and discussion: The DD 13C NMR experiments displayed significant differences in the HA spectral profiles as regards to the standard CPMAS 13C NMR acquisition conditions, mainly in the chemical shift region of alkyl structures as well as for tannin- or carbohydrate-like O-alkyl structures. In fact, the comparison between DD and CPMAS solid-state NMR suggested shortening of alkyl chains and generation of carbohydrate-derived, unsaturated structures—viz. furans—which adds to the aromatic domain. Pyrolytic results showed fire-induced specific changes in HAs chemical structure and its molecular diversity. The changes were evident in the location and sizes of the different clusters of pyrolysis compounds defined by their atomic ratios. Conclusions: The DD 13C NMR provided specific information on the fate of aliphatic structures and the origin of unsaturated HA structures, which could be helpful in differentiating “inherited” from “pyrogenic” aromatic structures. This is further confirmed by the analysis of the molecular assemblages of pyrolytic products, which showed accumulation of condensed polyaromatic domains in the HAs after the high-intensity fire, accompanied by a recalcitrant alkyl hydrocarbon domain. Medium-intensity fire led to aromaticity increase due to a selective accumulation of lignin-derived phenols concomitant to the depletion of aliphatic hydrocarbon constituents | Descripción: | 11 págnas.-- 2 figuras.-- 4 tablas.-- 37 referencias.-- Electronic supplementary material The online version of this article (doi:10.1007/s11368-016-1595-y) contains supplementary material, which is available to authorized users | Versión del editor: | http://dxdoi.org/10.1016/10.1007/s11368-016-1595-y | URI: | http://hdl.handle.net/10261/174008 | DOI: | 10.1007/s11368-016-1595-y | ISSN: | 1439-0108 |
Aparece en las colecciones: | (MNCN) Artículos (IRNAS) Artículos |
Ficheros en este ítem:
Fichero | Descripción | Tamaño | Formato | |
---|---|---|---|---|
Natural_organic_matter_chemistry_2018_Postprint.pdf | 1,18 MB | Adobe PDF | Visualizar/Abrir |
CORE Recommender
SCOPUSTM
Citations
22
checked on 18-mar-2024
WEB OF SCIENCETM
Citations
15
checked on 23-feb-2024
Page view(s)
383
checked on 27-mar-2024
Download(s)
301
checked on 27-mar-2024
Google ScholarTM
Check
Altmetric
Altmetric
NOTA: Los ítems de Digital.CSIC están protegidos por copyright, con todos los derechos reservados, a menos que se indique lo contrario.