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Dive into the research topics where Christian Di-Giovanni is active.

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Featured researches published by Christian Di-Giovanni.


Organic Geochemistry | 2003

Soil organic matter (SOM) characterization by Rock-Eval pyrolysis : scope and limitations

Jean-Robert Disnar; Bernard Guillet; Didier Kéravis; Christian Di-Giovanni; David Sebag

Application of Rock-Eval pyrolysis to soil organic matter (SOM) quantitation and characterization has been explored by the study of about 100 soil samples taken from a variety of soil profiles from different ecosystems at different latitudes. A straightforward illustration of these possibilities can be obtained from a Hydrogen Index (HI in mg hydrocarbons g−1 TOC) vs. Total Organic Carbon (TOC) diagram that effectively allows one to follow simultaneously the main qualitative (SOM hydrogen richness given by HI values) and quantitative (TOC) changes that affect SOM with increasing depth and humification, in the soil profiles. In addition, abnormally high Oxygen Index (OI in mg CO, CO2 or O2 g−1 TOC) values are fully diagnostic of extensive SOM alteration, as frequently observed in podzol B horizons. More detailed information on the heterogeneity of SOM and on its degree of evolution, can be gained from the shape of the pyrolysis S2 peak recorded in the course of programmed pyrolysis in an inert atmosphere (N2) and/or from its maximum temperature “Tpeak”. All these parameters and others, all determined rapidly and automatically, are particularly useful to screen major SOM variations within large sets of samples.


Global and Planetary Change | 2002

Estimation of the annual yield of organic carbon released from carbonates and shales by chemical weathering

Christian Di-Giovanni; Jean Robert Disnar; Jean Jacques Macaire

The aim of this paper is to propose an initial estimation of the annual organic matter yield induced by chemical weathering of carbonates and shales, considering their global surface at outcrop and their organic matter content. The calculation also uses data on river fluxes resulting from carbonate rocks and shales weathering in major world watersheds, published by numerous authors. The results obtained from the studied watersheds have then been extrapolated to a global scale. Despite rather large uncertainty to such an approach, the calculated value of ca. 0.1 Gt implies that the annual organic carbon yield related to carbonates and shales chemical weathering might be a non-negligible component of the global carbon cycle. The individual contributions of different watersheds necessarily depend on the organic matter content of altered rocks. They are also obviously controlled by climatic parameters. The calculated yields do not constitute a direct supply to soils and rivers because of mineralisation when organic carbon is brought in contact with the atmosphere. Even so, the release of fossil organic matter would have implications for the global carbon cycle through the efficiency of the global chemical weathering as a carbon sink. Whatever the chosen hypothesis, the results of this study suggest that the recycled organic yield is a neglected component in the global organic carbon cycle assessment. Because it exists and, in addition, because it might represent a non-negligible carbon pool, fossil organic carbon deserves to be taken into account for a better evaluation of the organic stocks in soils and rivers presently only based on climatic data and current vegetal production.


The Holocene | 2006

Quantification and regulation of organic and mineral sedimentation in a late-Holocene floodplain as a result of climatic and human impacts (Taligny marsh, Parisian Basin, France)

Jean-Jacques Macaire; Jacques Bernard; Christian Di-Giovanni; Florent Hinschberger; Nicole Limondin-Lozouet; Lionel Visset

Quantification in grams per metres squared per year of the sediment accumulation in a flood plain (‘marsh’) located in the southwestern Parisian basin showed that there is no close relationship between the accumulation of organic matter (OM) and mineral matter (MM) during the late Holocene, and provided an accurate view of the distinct yield and storage conditions of both sediment components. Endogenic OM accumulation in peaty sediments is not related to the climate but to felling of the alder forest and its substitution by Cyperaceae and paludal taxa in the marsh (Iron Age and Middle Ages). MM accumulation expresses mainly the sediment yield on the slopes, determined by landuse. During an initial phase (from the late Neolithic to the early Middle Ages), land-use change from crop cultivation to pastureland, possibly related to climate deterioration, led to a decrease in the sediment yield. During a second phase, since the early Middle Ages, the considerable development of crop cultivation over pasturing, even during periods of climate deterioration (such as the ‘Little Ice Age’), led to a sharp increase in sediment yield. However, although sediment yield was high, the hydrodynamics in the fen did not favour particle retention. Thus, since the Neolithic, yield and storage of OM and MM sediment have been marked by human activities, initially with high climatic stress, but since the Middle Ages without significant climatic stress.


The Holocene | 2013

Recent climatic and anthropogenic imprints on lacustrine systems in the Pyrenean Mountains inferred from minerogenic and organic clastic supply (Vicdessos valley, Pyrenees, France)

Anaëlle Simonneau; Emmanuel Chapron; Thierry Courp; Kazuyo Tachikawa; Gaël Le Roux; Sandrine Baron; Didier Galop; Marta Garcia; Christian Di-Giovanni; Mikael Motelica-Heino; Florence Mazier; Anthony Foucher; Thomas Houet; Marc Desmet; Edouard Bard

High-resolution seismic profiling has been combined with geochemical analyses of both watershed samples and five lacustrine cores retrieved from two natural lacustrine basins of glacial origin: Lake Majeur and Lake Sigriou (1630 m a.s.l. and 1995 m a.s.l., respectively, Eastern French Pyrenees). Identifying specific minerogenic and organic markers of autochthonous and allochthonous supply, data allow documenting past climatic and anthropogenic pressures. Over the past century, the lacustrine sediment of Lake Majeur has been essentially composed of algae, drastically contrasting with the natural sedimentary infill of the basin, mainly resulting from soil erosion from the mid–late Holocene. Since ad 1907, the Lake Majeur has been used for hydroelectricity production. Human-induced lake-level regulations, affecting up to 37% of the lacustrine surface, have increased by fourfold the accumulation rate of the lake and favoured water enrichment. Rubidium abundance within the lacustrine sediments of the two lakes reflects the mid–late Holocene palaeohydrology. After dam construction in ad 1907, greater quantities of rubidium found in Lake Majeur sedimentary infills indicate drier climatic periods, such as from ad 1975 to ad 1982, during which water reservoirs were particularly in demand. Inversely, before the dam was built, rubidium fluctuations were correlated with wetter conditions and hydrological events were recorded as sandy layers deposited by canyon reactivation, synchronous with European climatic deterioration phases. We notably document that the Mediaeval Climate Anomaly was interrupted by some humid periods dated c. ad 940, ad 1080, ad 1100 and ad 1250. We also date the onset of the ‘Little Ice Age’ c. ad 1360 and identify that this period was wetter after c. ad 1500.


Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule A-sciences De La Terre Et Des Planetes | 2000

Application de l'étude de la matière organique à l'analyse de l'érosion : exemple du bassin versant du Moulin, dans les terres noires des Alpes-de-Haute-Provence (France)

Christian Di-Giovanni; Jean-Robert Disnar; Jean-Paul Bakyono; Didier Kéravis; François Millet; Jean-Emmanuel Olivier

Abstract The present study is based on the optical (palynofacies) and geochemical (pyrolyse Rock–Eval) characterization of the organic matter occurring both in bedrock, soils, river sediments (suspended matter and bedload) in a Draix Erosional Research Basin (Cemagref). Results confirm firstly the contribution of reworked organic matter in modern fluxes. Numerous previous studies have shown that organic matter analysis can be an accurate tool to provide information concerning past climates and past environments. Present results suggests that such analysis can also give information concerning the characterization of eroded bedrocks and of erosional processes such as river bank erosion and runoff.


Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule A-sciences De La Terre Et Des Planetes | 1999

Des particules charbonneuses, témoins des variations de l'érosion chimique d'un bassin versant calcaire durant l'holocène (bassin de chaillexon, doubs, France)

Christian Di-Giovanni; Michel Campy; Jean-Robert Disnar

Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of this paper is to characterize chemical weathering variations in the past using coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaillexon lake, Doubs, France). Results point out that chemical weathering was the predominant erosional process in the watershed, which may be due to the calcareous nature of the bedrock. The significant variability of this process relative to mechanical weathering during the Holocene period can be interpreted as a consequence of the development of the vegetal cover induced by climate changes and human activity (forest clearing and landuse). Results also suggest that there is no direct relationship between chemical weathering in the watershed and autochthonous carbonate precipitation in the lake.


Climate of The Past Discussions | 2012

Multidisciplinary distinction of mass-movements and flood induced deposits in lacustrine environments : implications for Holocene palaeohydrology and associated natural hazards (Lake Ledro, Southern Alps, Italy)

Annaëlle Simonneau; Emmanuel Chapron; Boris Vannière; Stefanie B. Wirth; A. Gilli; Christian Di-Giovanni; Flavio S. Anselmetti; Marc Desmet; Michel Magny

A. Simonneau, E. Chapron, B. Vannière, S. B. Wirth, A. Gilli, C. Di Giovanni, F. S. Anselmetti, M. Desmet, and M. Magny ISTO, UMR7327, CNRS; Univ. Orléans; BRGM, 1A rue de la Férollerie, 45071 Orléans Cedex 2, France Laboratoire de Chrono-Environnement, UMR6249, CNRS; UFR des Sciences et Techniques, 16 route de Gray, 25030 Besançon, France Geological Institute, ETH Zurich, Sonneggstrasse 5, 8092 Zurich, Switzerland Eawag, Department of Surface Waters, Überlandstrasse 133, 8600 Dübendorf, Switzerland 3205


Earth Surface Processes and Landforms | 2018

Badlands as a hot spot of petrogenic contribution to riverine particulate organic carbon to the Gulf of Lion (NW Mediterranean Sea): POC flux from badlands to the NW Mediterranean sea

Yoann Copard; Frédérique Eyrolle; Olivier Radakovitch; Alain Poirel; Patrick Raimbault; Stéphanie Gairoard; Christian Di-Giovanni

Determining the riverine carbon fluxes to oceans is critical for an improved understanding of C budgets and biogeochemical cycles (C, O) over a broad range of spatial and time scales. Among the particulate organic carbon (POC) involved in these fluxes, those yielded by sedimentary rocks (petrogenic POC: pPOC) remain somewhat uncertain as to their source on continental surfaces. Based on time series from long‐term observatories, we refine the POC and sediments flux of the Rhone River, one of the major tributaries to the Mediterranean Sea. Radiocarbon measurements on a set of riverine samples and forward modelling were used to (i) determine a modelled pPOC content and pPOC/POC ratio for each sample set, (ii) assess pPOC flux delivered to the NW Mediterranean Sea, and (iii) estimate the badlands contribution from the Durance catchment to both the pPOC and to sediment discharges. The weighted pPOC flux contributes up to 26% of the POC flux (145 Gg yr‐1) discharged into the Mediterranean Sea, whereas the weighted pPOC content reaches 0.31 wt%. Despite their low contributive surface area (0.2%), badlands provide, respectively, 12, 3.5 and 14% of the pPOC, POC and sediment fluxes to the Rhone River. Consequently, such rocks can be considered as a major source of pPOC and sediments for the NW Mediterranean Sea and potentially for oceans. We suggest that river‐dominated ocean margins, such as the Rhone River, with badlands in their catchment could export a significant amount of pPOC to the oceans.


Earth-Science Reviews | 2006

Palynofacies as useful tool to study origins and transfers of particulate organic matter in recent terrestrial environments: Synopsis and prospects

David Sebag; Yoann Copard; Christian Di-Giovanni; A. Durand; B. Laignel; S. Ogier; Elisabeth Lallier-Vergès


Earth Surface Processes and Landforms | 1998

Geochemical characterization of soil organic matter and variability of a postglacial detrital organic supply (chaillexon lake, france)

Christian Di-Giovanni; Jean Robert Disnar; Vincent Bichet; Michel Campy; Bernard Guillet

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Claude Le Milbeau

François Rabelais University

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Jean-Jacques Macaire

François Rabelais University

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