WP 2- Degassing from the continental geobiosphere

The central topic of this WP is the evaluation of greenhouse gases (GHG) and volatile organic volatile compounds (VOOVCs) emissions from two three main continental settings: peatlands, and cultivated lands, and polluted sites. We primarily uses data gathered from monitored natural sites of the PIVOTS>PESA platforms (Tourbières and OS2 see https://plateformes-pivots.eu/), belonging to national or international networks, ensuring data integration on a global scale. The WP uses extensively the various platforms so far developed, notably HELIOS, and those of PIVOTS platform’s project (PESAa/t, PRIME, PRAT, O_ZNS). Modeling the measured fluxes of GHGGE/VOCsOVC is a key priority and this will be achieved using established models (ORCHIDEE-PEAT, LMDZ), which will be modified to fit the new data. The end goal is to constrain the GHG share on the global climate change of these specific land settings.

In detail the priority targets of WP2 are:

  • 1 In peatland settings, we aim at disentangling the role of hydric factors on the dynamic of degassing. We also study the reactivity of OVC VOCs and their reaction path once in the atmosphere, either in situ on in the field land or in the laboratory (e.g., using HELIOS, the largest and most equipped atmospheric simulation chamber in France and which is an ACTRIS experimental platformCIMS and ToF-CIMS)).
  • 2 In both settings, we aim at quantifying the fluxes of indirect emissions of GHG related to distal hydrosystems (degassing of water after their transit across production zones) using in particular isotopes to track the source.
  • 3 Equally, in both settings, we aim at evaluating the role of changing redox conditions of the soils on GHG and on the biotransformation of organic matter. The role of microbial activity in the rhizosphere zone is studied as well. More largely, the exact influence of biomass composition and activities to build reactive localized interfaces wherein geochemical gradients accumulate is one main axis of reflection. The concept of critical interface is the leading term to structure a deep conceptualization of how water, air, and biomass cooperate to result into unexpected behaviors.
  • 4 The characterisation of GHG and OVC VOCs needs a good understanding of the functioning of the the critical zone. Progress in this area is achieved by combining environmental monitoring with geophysical sensors on specific dedicated sites (by using the PESAa, PESAt, and O_ZNS PIVOTS platforms) and dedicated laboratory simulations, including the geological lab-on-a-chip techniques associated to high resolution spectroscopic measurements initiated in VOLTAIRE. The PESAa and PESAt platforms are dedicated to the measurements of GHG and VOCs, where the hydric functioning of the soil-atmosphere interface is continuously monitored over the 0 to 1 m depth. In particular, the O_ZNS instrument is devoted to the description of fluids exchanges over the whole unsaturated zone -– say down to 20 meters depth – and harness geophysical sensors (as the spontaneous potential, georadar and electrical imagings) to geochemical dynamical purposes characterisations, like the monitoring of following the unsaturated transfert signals, capillary fringe or and the delineating of the redox-active biomass zonation. This part is directly linked to the more macroscopic and mesoscale approaches developed in WP1 for the simulation and modelling of reactive transfer of fluids in porous and fissured media.

Knowledge gained from peatlands functioning under the drive of global warming will be useful for the evaluation of biomass burning (see WP3 below), which affects intensively each year Siberian peats.

Economic Impacts: valuing environmental damages and services
The earth-atmosphere exchanges due to human activities contribute widely to the emissions of GHG, but their economic valuation is still marginal, the only CO2 emissions to be priced coming from energy and industrial sectors through cap-and-trade-markets and carbon taxes. The main tool used in order to promote more environment-friendly practices are regulations, that are more or less stringent worldwide and can exert effects on international trade in resources that have been documented in VOLTAIRE 1. InAlong the same line, we document that international aid can also have a role to play in signing international environmental treatieses and trading natural resources worldwide. Another key issue is linked to the effect of agricultural practices and land use on GHG emissions that has also been studied during VOLTAIRE 1. These research strands will be continued and extended, through cooperation with the laboratories involved in the WP2. The main issue at stake in this field is linked to the valuation of ecosystemic services, and the development of circular economy, that involves also the WP1.