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Dynamics of soil organic matter amino acids : a carbon isotope approach / Dynamique des acides aminés des matières organiques des sols : approche par les isotopes stables du carboneKheir Beik, Louay 10 May 2017 (has links)
Cette thèse aborde un point clé du couplage entre ces cycles: la dynamique des molécules azotées (AAs) des matières organiques du sol (MOS). Par des expériences d'incubation, nous avons estimé que les flux de biosynthèse des AAs par les micro-organismes du sol lors du processus de décomposition sont de l'ordre de 25% de la biomasse nouvellement formée. Le profil des AAs individuels biosynthétisés de novo est plus dépendant du type de sol que de la nature du substrat. Dans chaque sol, il est très similaire à celui des AAs des MOS. La biodégradation de matériaux végétaux marqués en 13C a révélé la transformation rapide des protéines végétales en matériaux microbiens. Ces résultats montrent que les AAs des MOS sont d'origine microbienne. Nous avons mesuré le renouvellement du C des AAs à long terme dans les horizons de surface de neuf sites présentant des végétations, climats et types de sol variés, en utilisant la technique de traçage par les abondances naturelles en 13C. L'âge moyen du carbone des AAs varie de 50 à 200 ans. Un modèle simple permet de discuter les hypothèses du recyclage des AAs des MOS par les micro-organismes. Les rapports isotopiques stables des AAs individuels ont été mesurés par chromatographie en phase gazeuse couplée à la spectrométrie de masse isotopique. À cette fin, nous avons développé une méthode d'étalonnage générique pour la détermination du rapport isotopique des composés spécifiques, par analyse de cultures microbiennes uniformément marquées. Au-delà des résultats présentés, l'étude apporte un large ensemble de données des AAs et examine les variations de l'abondance naturelle en 13C entre les AAs individuels. / We analyzed the coupled dynamics of C and N in Soil Organic Matter (SOM) through the dynamics of N-containing soil organic compounds (amino acids (AAs)) by tracing their carbon atoms. Stable isotope ratios of individual amino acids were measured by gas chromatography coupled with isotope ratio mass spectrometry. For this purpose, we developed a generic calibration method for compound-specific stable isotope ratio analysis, based on the analysis of uniformly labelled microbial cultures. We quantified the biosynthesis of AAs associated with the biodegradation process in four contrasted topsoils through short-term incubation experiments of 13C-labelled substrates. Amino acids-C accounts for ca. 25% of the newly-formed microbial biomass-C. The composition of the de novo biosynthesized individual amino acids was dependent on the soil type, and in each soil was similar to that of SOM amino acids. Biodegradation of 13C-labelled plant materials revealed the rapid conversion of plant proteins into microbial materials. These results together demonstrate that SOM amino acids are of microbial origin. We measured the dynamics of amino acids-C on the long term (decades to centuries) in nine sites using the natural 13C-labelling technique. On average, the age of AAs was equal or slightly inferior to that of bulk soil organic carbon, with mean ages ranging from 50 to 200 years. We built a conceptual model of AAs dynamics to discuss various hypotheses of AAs stabilization. Beyond these perspectives on C and N coupling in soil processes, the overall study brings a broad dataset of amino acids, as well as discuses variations of 13C natural abundance (δ13C) in-between individual amino acids.
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Beyond the vessel: Organic residue analysis of Late Bronze and Early Iron Age south-east European potteryBastos, Beatriz I.F. de January 2019 (has links)
The Encounters and Transformations in Iron Age Europe project (ENTRANS) aims to expand our knowledge regarding the nature and impact of cultural encounters during the European Iron Age. The study of ceramic vessels was included in the project, in order to further understand cultural practices in the south-east Alpine region. Organic residue analysis is an important tool in archaeological research for determining the presence of food and other organic substances associated with ceramic vessels. It has the potential to significantly improve our understanding of Iron Age societies and the interactions between them. This research focuses on the analysis of visible and absorbed organic residues from 377 ceramic vessels, from Late Bronze Age and Early Iron Age sites in Slovenia and Croatia, by gas-chromatography mass spectrometry. Two methods of lipid extraction were compared in a pilot study compressing 30 potsherds from Kaptol (solvent vs. acid extraction). This study revealed that more information was obtained by acid extraction, thus it was selected as the main method of extraction for this project.
Differences between settlement, funerary and ritual sites were observed, suggesting that the vessels placed in the graves were not previously used or carried foodstuff with low lipid content, such as liquids and dry foods/cereals. Some types of residues were only identified in funerary vessels, specifically potential castor oil in Kaptol, mixed with other fats and oils. Lipid biomarkers and lipid ratios revealed significant differences between contexts and different sites, suggesting that the differences in cultural practices can also be identified in the use of ceramic vessels. Some residues were also sampled for gas-chromatography compound-specific isotope ratio mass spectrometry and bulk isotope analysis (only visible residues), which identified potential dairy fats in two potsherds from Poštela.
The results were also compared with the contextual information, mainly the faunal remains, and the data obtained from the osteology and diet study preformed with individuals from the same area and chronology as the ceramic vessels. / Encounters and Transformations in Iron Age Europe Project (ENTRANS);
Humanities in the European Research Area (HERA);
Institute Life Sciences Research (ILSR) University of Bradford.
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Distinguishing wild ruminant lipids by gas chromatography/combustion/isotope ratio mass spectrometryCraig, O.E., Allen, R.B., Thompson, A., Stevens, R.E., Steele, Valerie J., Heron, Carl P. January 2012 (has links)
No / RATIONALE: The carbon isotopic characterisation of ruminant lipids associated with ceramic vessels has been crucial for elucidating the origins and changing nature of pastoral economies. delta(13)C values of fatty acids extracted from potsherds are commonly compared with those from the dairy and carcass fats of modern domesticated animals to determine vessel use. However, the processing of wild ruminant products in pottery, such as deer, is rarely considered despite the presence of several different species on many prehistoric sites. To address this issue, the carbon isotope range of fatty acids from a number of red deer (Cervus elaphus) tissues, a species commonly encountered in the European archaeological record, was investigated. METHODS: Lipids were extracted from 10 modern red deer tissues obtained from the Slowinski National Park (Poland). Fatty acids were fractionated, methylated and analysed by gas chromatography/combustion/isotope ratio mass spectrometry (GCCIRMS). The delta(13)C values of n-octadecanoic acid and n-hexadecanoic acid, and the difference between these values (Delta(13)C), were compared with those from previously published ruminant fats. RESULTS: Nine of the ten deer carcass fats measured have Delta(13)C values of less than -3.3 per thousand, the threshold previously used for classifying dairy products. Despite considerable overlap, dairy fats from domesticated ruminants with Delta(13)C values less than -4.3 per thousand are still distinguishable. CONCLUSIONS: The finding has implications for evaluating pottery use and early pastoralism. The processing of deer tissues and our revised criteria should be considered, especially where there is other archaeological evidence for their consumption.
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Analysis of partially carbonised residues from the Chiseldon Cauldrons by gas chromatography-mass spectrometry and gas chromatography-combustion-isotope ratio mass spectrometrySteele, Valerie J. January 2017 (has links)
No / During the micro-excavation of the cauldrons, residues were identified which appeared different from the surrounding soil and metal corrosion products. Thirty-seven of these residues from nine cauldrons and two significant fragments of incomplete cauldrons were analysed by gas chromatography-mass spectrometry (GC-MS) along with two samples of soil from the micro-excavation for comparison. The aim of the analysis was to determine whether these residues contained any organic material related to the use of the cauldrons, specifically lipids (fats, waxes, resins etc.) from the preparation of food or drink. Two of the samples from the cauldrons were also sent for compound specific carbon stable isotope analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) to give a more precise identification of the residues.
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Structure of and carbon flux through soil food webs of temperate grassland as affected by land use managementLemanski, Kathleen 24 October 2014 (has links)
No description available.
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Olive oil or lard? Distinguishing plant oils from animal fats in the archaeological record of the eastern Mediterranean using gas chromatography/combustion/isotope ratio mass spectrometrySteele, Valerie J., Stern, Ben, Stott, A.W. 15 December 2010 (has links)
Yes / Distinguishing animal fats from plant oils in archaeological residues is not straightforward. Characteristic plant sterols, such as ¿-sitosterol, are often missing in archaeological samples and specific biomarkers do not exist for most plant fats. Identification is usually based on a range of characteristics such as fatty acid ratios, all of which indicate that a plant oil may be present, none of which uniquely distinguish plant oils from other fats. Degradation and dissolution during burial alter fatty acid ratios and remove short chain fatty acids, resulting in degraded plant oils with similar fatty acid profiles to other degraded fats.
Compound specific stable isotope analysis of ¿13C18:0 and ¿13C16:0, carried out by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS), has provided a means of distinguishing fish oils, dairy fats, ruminant and non-ruminant adipose fats but plant oils are rarely included in these analyses. For modern plant oils where C18:1 is abundant, ¿13C18:1 and ¿13C16:0 are usually measured. These results cannot be compared with archaeological data or other modern reference fats where ¿13C18:0 and ¿13C16:0 are measured, as C18:0 and C18:1 are formed by different processes resulting in different isotopic values.
Eight samples of six modern plant oils were saponified releasing sufficient C18:0 to measure the isotopic values, which were plotted against ¿13C16:0. The isotopic values for these oils, with one exception, formed a tight cluster between ruminant and non-ruminant animal fats. This result complicates the interpretation of mixed fatty residues in geographical areas where both animal fats and plant oils were in use. / AHRC
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