Soil carbon dioxide fluxes to atmosphere: The role of rainfall to control CO2 transport

Highlights: • Soil CO₂ gas concentration and fluxes were monitored before and after artificial rainfall event. • Results show significant effect of rainfall on CO₂ surface fluxes. • The recovery processes of soil CO₂ fluxes were very slow after rainfall event. In order to observe the relationships between the temporal variations of CO₂ surface fluxes and the CO₂ soil gas transport in soil profile before and during rainfall events, two experiments were conducted in a controlled natural environment at different time periods. These experiments consisted in injecting pure CO₂ in a lysimeter at 160 cm depth and simulating heavy rainfall event at its surface for 2 weeks. During the whole experiments, CO₂ soil gas concentrations and surface fluxes were continuously monitored. These measurements showed that the flux measured through the flux chamber were consistent with the concentration profiles. During simulated rainfall events, the concentrations and fluxes showed a clear change linked to the presence of water on the top of the water profile. The results clearly show a significant decrease of CO₂ flux to atmosphere induced by rainfall infiltration and consequential wash-out of the CO₂ present in the soil.