Composición y propiedades de la materia orgánica de las principales turberas españolas

Tesis Univ. Complutense de Madrid.Fac. de Ciencias BiológicasTRUEProQuestpu

Response of humic acid structure to soil tillage management as revealed by analytical pyrolysis

8 páginas.-- 5 figuras.-- 2 tablas.-- 34 referencias.-- 5 graficos suplementarios.The effects on the structural features of humic acids (HA) from dryland farming soils under long term management practices have been approached by analytical pyrolysis (Curie-point pyrolysis-gas chromatography/mass spectrometry, Py-GC/MS). The field experiments (started in 1987) include conventional, minimum and no-tillage plots, as well as non cultivated plots. The HAs isolated from the various plots showed significant differences in their pyrolytic behavior, in particular regarding the total abundances of alkyl pyrolysis compounds (fatty acids, alkenes and alkanes). The occurrence of very short-chain fatty acids (C5-C11) in uncultivated plots could be indicative of constitutional alkyl structures in the relictual HA from undisturbed soil. The effect of soil tillage managements substantially increased total abundances of fatty acids in plots under conservation practices (mainly no-tillage).The HAs from uncultivated soils showed the greatest percentages of alkanes and alkenes. This was associated to the increased proportions of even C-numbered alkene homologues from C12 to C18, possibly related to the incorporation of microbial compounds during the humification process. High percentage of alkylbenzenes and catechols were also characteristic of the uncultivated plots. The increased proportions of methoxyphenols, in special of the syringyl (dimethoxyphenyl) type, in HAs from plots subjected to conventional tillage pointed out to humification processes based on progressive alteration of plant lignins. From the viewpoint of soil quality, the results suggest comparatively advanced transformation stages of the HA from uncultivated plots, which means that conservation tillage practices seems to lead to increasing soil C levels, at expenses of the accumulation of comparatively recent organic matter derived either from altered lignins and/or microbial biomass. © 2015 Elsevier B.V.This work has been supported by the Spanish Ministry of Economy and Competitiess (Project CGL2013-43845-P) and the J CC Castilla-La Mancha (Project POII-2014-001-A).Peer reviewe

La oxidación con perborato como método para el estudio de la composición de biopolímeros orgánicos y de las sustancias húmicas del suelo

Comunicación presentada a la citada Bienal, celebrada del 16-20 de septiembre, 1985, en Barcelona, España.Se propone un método degradativo aplicable a las sustancias de tipo húmico basado en la des polimerización progresiva de la muestra por acción del peróxido de hidrógeno generado por un exceso de NaB02.H202 que reacciona simultáneamente con los propios grupos carboxilos del sustrato.Peer reviewe

Estudio de la naturaleza de las fracciones alteradas de lignina mediante degradación secuencial de la húmina heredada de los suelos

Comunicación presentada a la citada Bienal, celebrada del 16-20 de septiembre, 1985, en Barcelona, España.Es bien conocido que la elevada resistencia a la biodegradación de las ligninas se traduce en un largo periodo de residencia media incluso en los ecosistemas biológicamente más activos. Mientras que una parte de la lignina se convierte en compuestos de bajo peso molecular, también se acumula una fracción alterada que difiere del material de partida por la pérdida de grupos metoxilo e incorporación de grupos oxigenados y nitrogenados. En el caso del humus de los suelos, dichos procesos se conocen como de humificación directa, y conducen a la formación de la húmina heredada.Peer reviewe

Pyrolysis-GC-MS analysis of the formation and degradation stages of charred residues from lignocellulosic biomass

The structural transformations undergone by lignocellulosic biomass (freeze-dried rye grass, Lolium rigidum) subjected to progressive isothermal heating (burning at 350°C under oxidizing conditions for 30, 45, 60, 75, and 90 s) have been monitored by Curie-point pyrolysis-gas chromatographymass spectrometry (Py-GC-MS). The pyrograms suggest that even charred residues after severe heating (carbon loss ca. 50%) still contain substantial concentrations of some resistant plant structural components. Several trends were observed when monitoring the relative concentrations of the different groups of pyrolysis compounds released during successive charring stages: (i) the tetrapyrrole moiety of chlorophylls is rapidly destroyed as indicated by the decreasing yields of pyrroles and pyrrolines, whereas the phytol backbone is comparatively more resistant, leading to phytadienes after dehydration and reduction; (ii) the increasing yields of imidazoles from progressively heated samples (maximum at 45 s stage) suggest accumulation of newly formed nitrogen-containing compounds that may survive natural fires; (iii) the lignin backbone shows a relative resistance, the yields of aromatic products pointing to progressive demethoxylation; and, (iv) a selective accumulation of recalcitrant alkyl material occurred, which is interpreted as the result of thermal condensation of hydrocarbons and fatty acids into macromolecular materials in the charred residue. In terms of the intensity of the isothermal heating, the yields of the different classes of alkyl compounds follow the order phytadienes < fatty acids < alkanes < wax esters < sterols.Peer Reviewe

Carbon storage and stability of soil organic matter in a coffee agroecosystem in Sierra Sur de Oaxaca, Mexico

We evaluated the ability of the soils in a shade coffee agroecosystem under different handling conditions to accumulate stable forms of carbon in the Sierra Sur of Oaxaca, for this we quantify the soil carbon store and performed the isolation and chemical characterization of soil organic matter by chemical fractionation, UVvisible and infrared spectroscopy in the first 40 cm depth. Results showed no significant differences in carbon stores between handling conditions, reaching mean values 150 Mg C ha-1 . Humification patterns are consistent for all soils and indicate that over 50% of soil organic matter found in the insolubilization humins and between 15 and 20% are humic acids. This fraction, presumably the most stable, is made up of molecules whose aromatic and maturation has a positive relationship with increasing altitude and clay content. According to the above confirms the ability of shade-coffee agroecosystems to accumulate high carbon content associated with stable forms of soil mineral fraction.Se evaluó la capacidad de los suelos de un agroecosistema cafetalero de sombra bajo diferentes condiciones de manejo para acumular formas estables de carbono, en la Sierra Sur de Oaxaca; para ello, se cuantificó el almacén de carbono edáfico y se realizó el aislamiento y caracterización química de la materia orgánica del suelo mediante fraccionamiento químico, espectroscopía UV-visible e infrarroja en los primeros 40 cm de profundidad. Los resultaron no mostraron diferencias significativas para los almacenes de carbono entre condiciones de manejo, situándose en valores promedio de 150 Mg C ha-1. Los patrones de humificación son consistentes para todos los suelos e indican que más del 50 % de la materia orgánica del suelo se encuentra en las huminas de insolubilización y entre el 15 y 20 % corresponde a los ácidos húmicos. Esta fracción, presumiblemente la más estable, está conformada por moléculas cuya aromaticidad y maduración tiene una relación positiva con el incremento de altitud y el contenido de arcillas en el suelo. De acuerdo a lo anterior se corrobora la capacidad de los agroecosistemas cafetaleros bajo sombra para acumular elevados contenidos de carbono en formas estables asociadas con la fracción mineral del suelo.Consejo Nacional de Ciencia y Tecnología Posgrado en Ciencias Biológicas, UNA

Comparative analysis of the alkyl breakdown products from soil humic acids by thermal and wet chemical degradation methods

6 pages. Comunicación presentada al citado simposio, celebrado del 17-20 de septiembre, 2002, en Leoben (Austria).Total amounts and distribution patterns of alkyl degradation compounds were analyzed in soil humic acids isolated from a variety of continental Mediterranean ecosystems in Central Spain. Soil physical and chemical characteristics, humic acid composition and biomarker assemblages were studied in 16 representative, undisturbed or degraded forest ecosystems including broad-leaved autochthonous forests, bush formations, cultures, pastures and pine forests. The humic acid fraction of these soils was previously characterized by routine spectroscopic methods (UV-visible, FTIR, 13C and 15N CPMAS NMR). In the present study qualitative and quantitative features of the alkyl domain of humic acids are examined by comparing the structural information provided by independent destructive techniques, with special emphasis on the mild alkaline degradation (sodium perborate) and thermal degradation by Curie-point pyrolysis.Peer reviewe

StructuraI correlation between soil humins and kerogens as seen by analyticaI pyrolysis

3 pages, 1 figure, 1 table, 10 references. Publicación incluida en: Select papers from the 17th International Meeting on Organic Geochemistry. 4-8/09/1995, San Sebastián, España.The possibility of the accumulation in soils of stable aliphatic materials has been postulated as a non-exclusive altemative to classical models for humus formation, based on the selective preservation of aromatic biomacromolecules. Such a hypothesis represents an actualistic approach to the formation process of fossil organic sediments and conforms to recent findings regarding the humification process in specific compartments in active terrestrial soils. In order to bring sorne light into this possible connection we investigated the pyrolytic behaviour of humin preparations isolated by two physical methods.Peer reviewe

Melanins and lipids in Lycoperdon perlatum fruit bodies

5 pages, 1 figure, 3 tables, 27 references.After sequential degradation with sodium persulphate and potassium permanganate, the characteristics of the dark pigments from the soil gasteromycete Lycoperdonperlatum were described. Several aromatic acids (phenolic and benzenecarboxylic) were detected by glc-ms of the degradation products, but the aliphatic content of these polymer fractions was predominant, containing a high proportion of protein and showing fatty acids similar to those previously found in the lipid fraction. An acid soluble fraction of melanin, of a highly aliphatic nature, was also present in Lycoperdon fruit bodies.Peer reviewe