The behaviour of diborane-reduced fulvic acids in flash pyrolysis

7 pages, 3 figures, 1 table, 25 references.-- Publicado en el capítulo: Session 1: Isolation, Fractionation, and Characterization.-- Humic Substances in the Aquatic and Terrestrial Environment, Proceedings of an International Symposium, celebrado del 21-23, agosto, 1989 en Linköping, Suecia.-- Este volumen 33, referido en la Citación, consta de 514 páginas, 150 figuras y 57 tablas.It is suggested that the striking structural changes introduced in humic substances by reduction with diborane may be useful in studying the role of carboxyl groups in the behaviour of these substances in flash pyrolysis. In the preliminary results shown in this communication, pyrograms of two fulvic acids of different origins and the corresponding diborane reduced substances are compared. It was found that the diborane reduction was responsible for both qualitative and quantitative changes in the pyrolytic patterns of the fulvic acids. These patterns feflect the changes in the reactivity and structural stability of the fulvic materials caused by the disappearance of the carboxyl groups.Peer reviewe

Fulvic acids from particulate matter of a water-logged peatland

6 pages, 3 figures, 2 tables, 29 references.The presence of aggregates of humic substances (HS) with inorganic adsorbates in a lagoon located in Huelva (south Spain) is reported. The chemical nature of the fulvic acid (FA) fraction, extracted from the natural aggregate by treatment with chelating resins, has been investigated by physical and chemical methods. The results suggest that these FA are similar to FA from other aquatic environments. As revealed by FT-IR and NMR spectroscopies and mild oxidation with potassium persulfate, the FA contain predominantly in their structure polysaccharides and components derived from lignin.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

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

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

Biomarkers in the bitominous fraction of a spanish brown coal

8 pages, 5 figures, 2 tables, 19 references.Molecular indicators such as diterpenoid and triterpenoid hydrocarbons and steroid alcohols and ketones have been identified in the bituminous fraction of the lignite from Arenas del Rey (AR), South Spain. Diterpenoid hydrocarbons consists mainly of kaurenes and are indicati ve of higher plant contributions, specially from conifer resins. Triterpenoids consist mainnly of 17beta(H),21beta{H)-hopanes derived from recent biogenic activity which indicates the geological immaturity of this lignite and implies that it has undergone only a mild thermal history. Sterols consist of cholesterol, carmpesterol, stigmasterol and beta-sitosterol and their distribution suggests a possible phytoplankton input, which should confirm the geological hypothesis that this sediment had an estuarine or deltaic origin. Occurrence of stanones with the biological 5alfa configuration was also observed.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

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

Targeted aspect-based emotion analysis to detect opportunities and precaution in financial Twitter messages

Microblogging platforms, of which Twitter is a representative example, are valuable information sources for market screening and financial models. In them, users voluntarily provide relevant information, including educated knowledge on investments, reacting to the state of the stock markets in real-time and, often, influencing this state. We are interested in the user forecasts in financial, social media messages expressing opportunities and precautions about assets. We propose a novel Targeted Aspect-Based Emotion Analysis (tabea) system that can individually discern the financial emotions (positive and negative forecasts) on the different stock market assets in the same tweet (instead of making an overall guess about that whole tweet). It is based on Natural Language Processing (nlp) techniques and Machine Learning streaming algorithms. The system comprises a constituency parsing module for parsing the tweets and splitting them into simpler declarative clauses; an offline data processing module to engineer textual, numerical and categorical features and analyse and select them based on their relevance; and a stream classification module to continuously process tweets on-the-fly. Experimental results on a labelled data set endorse our solution. It achieves over 90% precision for the target emotions, financial opportunity, and precaution on Twitter. To the best of our knowledge, no prior work in the literature has addressed this problem despite its practical interest in decision-making, and we are not aware of any previous nlp nor online Machine Learning approaches to tabea.Xunta de Galicia | Ref. ED481B-2021-118Xunta de Galicia | Ref. ED481B-2022-093Financiado para publicación en acceso aberto: Universidade de Vigo/CISU