Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES European Journal of Soil Science e70041 [5 p.] biogenic carbonate calcareous soils isotopic signature lithogenic carbonate Mediterranean soils FRANCE ZONE MEDITERRANEENNE 2025 fdi:010092695 ENG European Journal of Soil Science 1351-0754 ISI:001408449100001 1 10.1111/ejss.70041 https://www.documentation.ird.fr/hor/fdi:010092695 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-03/010092695.pdf 76 Horizon (IRD) Studying the soil organic and inorganic carbon (SOC and SIC) dynamics is essential to assess the carbon (C) sequestration potential of calcareous soils. Isotopic signatures (delta C-13) are used to assess the C origin of SOC or SIC. However, as measuring SOC and SIC contents, measuring delta C-13(SOC) and delta C-13(SIC) on a non-pretreated aliquot remains a challenge. Thermal analyses, like the Rock-Eval (RE) analysis, are promising to quantify SOC and SIC in a single analysis, but, to our knowledge, no development was conducted to assess delta C-13(SOC) and delta C-13(SIC). We coupled a RE device to an isotopic gas analyser (Picarro) to continuously measure delta C-13(CO2) and approach delta C-13(SOC) and delta C-13(SIC). We hypothesised that different carbonate mineralogies and/or crystal sizes in SIC involve fluctuations of the delta C-13(CO2). Two calcareous soils, a lithogenic (calcite) and a biogenic (snail shell) carbonate, and five calcite/shell mixes were analysed with the RE-Picarro setup. Two distinct delta C-13(CO2) values were obtained before and after 650 degrees C and were consistent with the delta C-13(SOC) and delta C-13(SIC) obtained by EA-IRMS. The fluctuations of delta C-13(CO2) above 650 degrees C were higher with calcite/shell mixes than with pure carbonates. A delta C-13(CO2) fluctuation > +/- 0.2 parts per thousand could be a pertinent indicator to detect mixes of carbonate with different delta C-13 in soils. The RE-Picarro setup is promising to assess SOC and SIC contents, delta C-13(SOC) and delta C-13(SIC) and detect mixes of carbonate with different origin on a non-pretreated aliquot. Development is needed (i) on more soil and carbonate samples and (ii) to improve the precision and accuracy of the RE-Picarro setup. 068 UR210