Continuous and long-term measurement of the partial pressure of dissolved CO₂ (pCO₂) in aquatic environments—rivers, lakes, or groundwater—is essential to improve the quantification of carbon fluxes, particularly outgassing, but also ecosystem metabolism, as a complement to dissolved oxygen measurements.

Over the past decade, several developments have emerged, notably infrared sensors coupled with extraction systems—either passive, using gas measurement in a headspace behind a membrane, or “active,” involving air pumping and circulation through a silicone tube. Commercial sensors developed for oceanography are available but remain expensive. Current research is progressing toward the use of low-cost sensors (Bastviken et al., 2015 ; Fietzek et al., 2014), and even toward the use of optodes. The TERRA FORMA project supports advancements in these developments by evaluating several types of sensors :

• An autonomous commercial sensor with a flat membrane ensuring water–air equilibration,
• An atmospheric sensor integrated into a sintered Teflon casing for equilibration and sealing,
• A low-cost atmospheric sensor embedded in a 3D-printed housing with a membrane for equilibration.

The developments and tests conducted both in the lab and in the field will help establish a qualification protocol for dissolved gas sensors. These sensors and their dataloggers will be deployed at TERRA FORMA test sites and other catchments or study sites.

Themes : Water Resources, Pollution

Updated on 21 juin 2025