Hazera J., Kowalewski I., Sebag D., Verrecchia E., Ravelojaona H., Chevallier Tiphaine. (2025). Coupling infrared isotopic gas analysis and thermal ramped analysis to characterise soil organic and inorganic carbon. European Journal of Soil Science, 76 (1), p. e70041 [5 p.]. ISSN 1351-0754.
Titre du document
Coupling infrared isotopic gas analysis and thermal ramped analysis to characterise soil organic and inorganic carbon
Hazera J., Kowalewski I., Sebag D., Verrecchia E., Ravelojaona H., Chevallier Tiphaine
Source
European Journal of Soil Science, 2025,
76 (1), p. e70041 [5 p.] ISSN 1351-0754
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.
