Recent advances in the application of stable isotope ratio analysis in forensic chemistry

This review paper updates the previous literature in relation to the continued and developing use of stable isotope ratio analysis in samples which are relevant to forensic science. Recent advances in the analysis of drug samples, explosive materials, and samples derived from human and animal samples are discussed. The paper also aims to put the use of isotope ratio mass spectrometry into a forensic context and discuss its evidential potential

Efficient organic carbon burial in the Bengal fan sustained by the Himalayan erosional system

Author Posting. © Nature Publishing Group, 2007. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 450 (2007): 407-410, doi:10.1038/nature06273.Continental erosion controls atmospheric carbon dioxide levels on geological timescales through silicate weathering, riverine transport and subsequent burial of organic carbon in oceanic sediments. The efficiency of organic carbon deposition in sedimentary basins is however limited by the organic carbon load capacity of the sediments and organic carbon oxidation in continental margins. At the global scale, previous studies have suggested that about 70 per cent of riverine organic carbon is returned to the atmosphere, such as in the Amazon basin. Here we present a comprehensive organic carbon budget for the Himalayan erosional system, including source rocks, river sediments and marine sediments buried in the Bengal fan. We show that organic carbon export is controlled by sediment properties, and that oxidative loss is negligible during transport and deposition to the ocean. Our results indicate that 70 to 85 per cent of the organic carbon is recent organic matter captured during transport, which serves as a net sink for atmospheric carbon dioxide. The amount of organic carbon deposited in the Bengal basin represents about 10 to 20 per cent of the total terrestrial organic carbon buried in oceanic sediments. High erosion rates in the Himalayas generate high sedimentation rates and low oxygen availability in the Bay of Bengal that sustain the observed extreme organic carbon burial efficiency. Active orogenic systems generate enhanced physical erosion and the resulting organic carbon burial buffers atmospheric carbon dioxide levels, thereby exerting a negative feedback on climate over geological timescales

Contribution à l'étude des saisies d'Ecstasy par spectrométrie de masse de rapports isotopiques (apport du rapport 15N/14N)

Illicit drugs have always been used by humans. With scientific progress, new drugs appear each year. At the present time, in France, Ecstasy is the most widespread illicit synthetic drug. The term Ecstasy generally refers to tablets containing 3,4-méthylendioxy-methamphetamine (MDMA). In order to struggle against traffics of drugs of abuse, many methods can be employed. In this study, 13C/12C and 15N/14N ratios of MDMA samples were measured by isotopic techniques, in particular by using a Gas chromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS). The aim of such analyses was to confirm that links exists between precursors, synthetic pathways and MDMA, and in the same way to establish links between drug seizures...NANTES-BU Sciences (441092104) / SudocSudocFranceF

Evolution of paleoclimatic conditions and vegetation change in Himalaya from compound specific hydrogen and carbon analyses

Supplied by the Ganga–Brahmaputra fluvial system, the Bengal Fan provides an integrated record of the Himalayan basin history through time. The active channel-levee system of the middle fan documents the last glacial/interglacial cycle. Organic geochemistry studies have shown that the organic matter contained in the Bengal Fan sediments is mainly of terrestrial origin. We analysed terrestrial n-alkanes (C27–C33) from Bengal Fan sediments and modern Ganga–Brahmaputra sediments. Comparison of compound specific hydrogen and carbon isotopic ratios in these samples allow us to follow the evolution of paleoenvironmental conditions since the Last Glacial Maximum. Carbon molecular isotopic data on the odd-HMW n-alkanes show a shift of 4&, corresponding to an evolution in the Himalayan system from a C4-dominated vegetation at LGM to a C3- dominated vegetation during the Holocene. It is now well known that C4 plants are more adapted than C3 plants to low atmospheric CO2 concentrations and to relatively hot and dry climate. In the same time, molecular D/H isotopic ratios measured on the same samples show an increase of the deuterium content of about 20& during the Holocene, which is consistent with lower temperature at the end of the LGM in the Himalaya. As low temperature should favored C3 plants, the predominance of a C4 vegetation have to be linked with dryer conditions at the end of the LGM. Afterwards, the increase of the C3/C4 ratio in the Himalayan system is related to a concomitant increase of humidity and pCO2 during the Holocene

Methoxylated fatty acids in Blumeria graminis conidia

International audienceThe total fatty acids (FA) composition of Blumeria graminis f.sp. tritici conidia, the causal agent of wheat powdery mildew, was analyzed as a function of their age. A total of 19 FA (C 12–C 24 saturated and unsaturated) and unusual methoxylated fatty acids (mFA) were detected in young, intermediate and old conidia. Two very long chain methoxylated FA were identified by GC–MS as 3-methoxydocosanoic and 3-methoxytetracosanoic acids. Medium chain FA were predominant in young conidia (75%, including 13% of mFA) while very long chain fatty acids constituted the major compounds in old conidia (74%, including 30% of mFA). We have shown for the first time that the total FA composition is strongly correlated with the age of B. graminis f.sp. tritici (Bgt) conidia

Karelianite and vanadian phlogopite from the merelani hills gem zoisite deposits, Tanzania.

International audienc

C4 plants decline in the Himalayan basin since the Last Glacial Maximum

The Bengal Fan turbiditic system, supplied by the Ganga-Brahmaputra river system, provides an integrated record of Himalayan system erosion. Thanks to minor inputs of marine organic matter and almost complete preservation of riverine organic carbon, organic matter buried in Bengal Fan sediments is a proxy of Himalayan basin paleo-vegetation. The active channel-levee system of the middle fan documents the last 19 ka and allows the reconstruction of vegetation change in the Himalayan basin since the Last Glacial Maximum (LGM). We measured delta C-13 of organic carbon (C-org) in order to track changes in the proportions of C3 and C4 plants in the Himalayan basin. From LGM to mid-Holocene, delta C-13 of bulk C-org shifts of 3-4%. towards more negative values. Relative abundance of individual n-alkanes reveals that terrestrial higher plant inputs represent a dominant fraction of C-org buried in Bengal Fan sediments. delta C-13 of higher plants biomarkers mimic that of bulk C-org showing that the later can be used as continental paleo-vegetation proxy. delta C-13 negative shift from LGM to mid-Holocene, mostly indicates the transition from a dominant input of C4 plants to a dominant input of C3 plants and therefore reveals that C4 plants were more abundant in the basin under glacial conditions. Vegetation repartition in the basin simulated using the CARAIB dynamic vegetation model is consistent with C-org data. The model indicates a dominance of C4 plants in the Gangetic plain during the LGM while eastern part of the basin remains dominated by C3 plants. The comparison between our data and proxies of regional paleo-climate suggests that the large decline of C4 plants after the LGM was due to combined increase of atmospheric CO2 and humidity levels. Integrated record of Himalayan basin paleo-vegetation suggests more and conditions during the LGM than during the mid-Holocene and agrees with reconstructions of the monsoon indicating stronger SW monsoon during interglacial and stronger NE monsoon during glacial periods. (C) 2008 Elsevier Ltd. All rights reserved