Baseline Subsoil Co2 Gas Measurements And Micrometeorological Monitoring: Above Canopy Turbulence Effects On The Subsoil Co2 Dynamics In Temperate Deciduous Forest

Featured ApplicationThis work emphasizes the importance of the deep soil zone and above groundwater that can be applied to create a CO2 baseline for a wide range of geological storage applications.Accurate and continuous measurement of the subsoil CO2 is critical to better understand the terrestrial and atmosphere gas transfer process. This work aims to develop and field test a specific flow system to continuously measure the soil gas concentration (chi c) and understand its main physical drivers. Hourly data measured in situ were collected through two dedicated wells at 1 m and 6 m depth coupled with micrometeorological measurement. Our study shows that chi c at -1 m was at the lowest in winter and highest in summer. Meanwhile, the seasonal variation of chi c at -6m is somewhat unclear. While it is inevitable that temperature plays a significant role, this factor related to biological activity cannot fully explain the variation. The decrease in chi c at both depths in summer coincides with an increase of friction velocity, especially during dry periods with R-2 of 0.68, which shows strong empirical evidence that wind turbulence plays a significant role in driving the deep soil CO2. A monitoring strategy for gas measurement combining borehole and micrometeorological measurement offers excellent long-term monitoring possibilities to derive the vertical distribution of CO2 and better understand the main physical drivers of gas exchange.