Contribution à l'étude structurale par PY/CG-SM de la matière organique liée aux particules fines (0-50 µm) dans quelques sols sous formations naturelles de longue durée au Burkina Faso

Contribution to the study by PY/GC-MS of organic matter linked to fine particles (0-50 µm) in some soils under long-term natural formations in Burkina Faso. The study aims to enhance the knowledge on organic matter of Arenosols, Ferralsols, and Cambisols in Burkina Faso. It deals with the distribution of C and N in three particles size fractions and is focused on the structures of organic matter linked to the (0-50 µm) fraction. The results showed that total organic matter was lower than 2% in all soil units. More than 70% of total carbon were held by the finest fraction. The main products released by PY/GC-MS technique of the (0-50 µm) fraction were lignin derived compounds, non lignin derived aromatic compounds, carbohydrates derived compounds, fatty acids methyl esters and nitrogen derived compounds. The aliphatic compounds ranged from C12 to C18, C16 being the dominant one. The aliphatic compounds were negatively correlated with the aromatic compounds. A positive correlation was observed between the nitrogen derived compounds and the amounts of clay. On the other hand, the carbohydrates derived compounds were negatively correlated with clay particles. Furthermore, the study pointed out some different structures of lignin such as syringyl, guaiacyl, and p.hydrophenyl. Depending on the nature of wood (hard wood, soft wood and grasses), they reflected the composition of vegetation on the studied sites. Therefore, PY/GC-MS technique was efficient for structural characterization of low amounts of soil organic matter

Micromorphological and chemical investigation of late-Viking age grave fills at Hofstaðir, Iceland

Grave fills from seven human burials from a late-Viking age - early medieval cemetery at Hofstaðir, Mývatnssveit (Iceland) were examined by soil micromorphology and organic chemical analysis. Detailed analysis of the weathering of the mineral constituents of the grave fills demonstrates a relationship between the extent of weathering of volcanic silicates within the fills and the presence of buried human remains. Gas chromatography-mass spectrometry (GC–MS) of extracts from the fills and controls of two graves revealed organic signatures dominated by plant-derived organic matter, with no evidence of degradation products of the body tissues. Transformation of n-alkanes into n-alkan-2-ones provides evidence for microbial activity within the fills. GC–MS analysis of the organic extract from under one of the skulls and pyrolysis gas chromatography of wood fragments found in that grave provide compelling evidence for the former presence of a conifer wood coffin. The use of this non-native wood in the burial provides evidence for either the import of foreign lumber or the utilisation of driftwood, most likely originating from Russia/Siberia

Structural study of the Moroccan Timahdit (Y-layer) oil shale kerogen using chemical degradations

International audienceThis paper deals with the structural characterization of the Moroccan Timahdit (Y-layer) oil shale kerogen. For this purpose, the kerogen concentrate was submitted to stepwise hydrolysis under phase transfer catalysis conditions. The results show that aliphatic and aromatic dicarboxylic acids are involved in the cross-linking of the kerogen matrix, acting as bridges, while aliphatic and aromatic monocarboxylic acids, and alcohols represent monosubstituents of the matrix. Aliphatic mono- and dicarboxylic acids are produced on ruthenium tetroxide oxidation of the kerogen. These acids arise from a variety of reactions including cleavage of ester linkages. 17α(H),21β(H)- and 17β(H),21α(H)-hopanoic acids, probably bound to the kerogen by ether groups, were identified in the oxidation products

Structure elucidation of soil macromolecular lipids by preparative pyrolysis and thermochemolysis

International audienceThe structure of macromolecular lipids from an acid anmoor soil was investigated using preparative pyrolysis and thermochemolysis. The matrix is formed by cross-linked aliphatic chains. Alkanols, triterpenoid alcohols e.g. a-amyrin, sterols, stanols can be bound to the matrix via ether or ester groups. Fatty acids can be incorporated through ester- i®cation. Dicarboxylic acids and other compounds such as hydroxyacids represent alkyl bridges between the poly- methylene chains. Various components are trapped in the macromolecular network. The two techniques give complementary results. Despite higher yields, thermochemolysis does not permit one to distinguish between methyl ester groups present in the structure and methyl ester groups formed on degradation