Mediterranean Peatland Water, Gas, and Soil content (Moltifau peatland, Corsica Island, France)
Description
The present dataset is part of a research that aims to status the carbon storage function of a Mediterranean peatland in changing climate conditions. The scientific strategy relies on a seasonal geochemical survey sourcing the carbon origin in peatland water and interfaces with the atmosphere. This research on a representative Mediterranean peatland reveals the seasonality of hydrochemical processes and dissolved carbon inputs from primary production, organic matter oxidation, and time-changing recharge components within the catchment (atmospheric water, river water, shallow groundwater, deep groundwater). Mixing proportions of all recharge components known (Santoni et al., 2021), the study applies a “reverse” end-member mixing analysis to define the theoretical peat water δ13C-DIC value and compare it to the measured one. The model explains 65 % of the data, demonstrating the watershed's influence on peatland carbon content—such terrestrial carbon fluxes toward a peatland needed to be reported and quantified. Furthermore, in 35% of the cases, peatland processes such as primary production and organic matter oxidation drive the peat water's carbon content. Then, δ18O, δ2H, peat organic and inorganic properties, δ13C-TOC, and 13C-CO2 data demonstrate the dominance of primary production, evidencing the role of groundwater in CO2 production and carbon storage capacity of the Mediterranean peatland. This research proves the relevance of geochemistry and isotope hydrology tools to disentangle and rank peatland water and carbon processes. Thus, it constitutes an innovative methodology designed to provide the key elements to consider in order to set up a carbon balance diagnosis of peatlands worldwide. Overall, the present research reveals the necessity to consider the interactions between water and carbon cycle processes, with particular consideration for groundwater as a CO2 source at the peatland-atmosphere interface, to build better models for the future evolution of the global climate. (Publication in process)
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Water physic-chemical parameters (EC, T, pH, Eh, DO) measured in situ with a Cond 3310 meter (WTW GmbH, Weilheim, Germany). Alkalinity determined in situ with a titrator (Hach Company, Loveland, USA). Major ions determined using a Dionex ICS 1100 chromatography (Thermo Fisher Scientific, Waltham, USA) at the University of Avignon, France. Precision better than 5 %. δ18O and δ2H determined with a liquid-water stable isotope analyzer DLT-100 (Los Gatos Research, San Jose, USA) at the University of Corsica, France. Precision better than 0.1 ‰ for δ2H and 0.01 ‰ for δ18O%. 3H determined by electrolytic enrichment and liquid scintillation counting method at the University of Avignon, France. Precision better than 5 % DIC content was determined from field alkalinity and pH measurements, DOC and TOC determined using a TOC 700 analyzer (Bioritech Industry, France) at the University of Avignon, France. Precision better than 5 % The CO2 from water samples was extract by acid etching, the CO2 from soils by in situ vacuum extraction. The δ13C of the CO2 fractions ( δ13C-DIC, 13C-CO2) were measured using Thermo Fischer Scientific (Bremen, Germany) Delta S isotope ratio mass spectrometer at the University of Avignon, France. Precision better than 10 %. Peat total nitrogen, hydrogen and carbon abundances (%) were determined using a CHNS Flash EA 1112 elemental analyzer (Thermo Scientific, Milan, Italy) at the University of Lausanne (ISTE-UNIL), Switzerland. The type and amount of organic matter were determined at ISTE-UNIL using a Rock-Eval ® 6 thermal analysis device according to Espitalie et al. (1985) and Behar et al. (2001). The calculated parameters included TOC (wt.%), hydrogen index (HI, mg hydrocarbons g-1 TOC), oxygen index (OI, mg CO2 g-1 TOC), and temperature of maximum pyrolysis yield (Tmax, ºC). The calibration was performed with the IFP 160000 standard (IFP, French Institute of Petroleum, Paris, France), with a precision better than 0.1%. The whole-peat mineralogy was determined by X-ray diffractometry (XRD) using a X-TRA Thermo-ARL Diffractometer (Thermo Fischer Scientific, Waltham, USA) according to the Kübler’s procedure (Kübler, 1997) at ISTE-UNIL. The semi-quantitative estimation (in %) of the grain minerals had a precision of 5% and 5–10% for phyllosilicates. The files generated are transformed into calculated files by the software WinXRD 2.0-6 (ThermoFischer program, Lausanne) using a fast Fourier noise filter, background subtraction and Ka2 stripping. The peat organic carbon δ13C values were determined in decarbonated samples using an elemental Carlo Erba 1108 EA analyzer (Fisons Instruments, Milan, Italy) connected to a Delta V Plus isotope ratio mass spectrometer (Thermo Fischer Scientific, Bremen, Germany) at the IDYST-UNIL.