New application of low cost sensors for continuous CO₂ flux measurements

Soil CO2 emissions are one of the largest contributions to the global carbon cycle, and a full understanding of processes generating them and how climate change may modify them is needed and still uncertain. Thus, a dense spatial and temporal network of CO2 flux measurements from soil could help reduce uncertainty in the global carbon budgets. In the present study, low cost Air Enquirer kits, including CO2 and environmental parameters sensors, have been designed, built and applied for the first time to design, develop and test a new Steady-State-Through-Flow (SS-TF) chamber for simultaneous measurements of CO2 fluxes in soil and CO2 concentrations in air. Sensor's responses were previously corrected for temperature, relative humidity, illumination and pressure conditions in order to reduce the uncertainty of measured CO2 values and of the following calculated CO2 fluxes. CO2 soil fluxes measured by the proposed SS-TF and by a standard closed Non-Steady-State-Non-Through-Flow (NSS-NTF) chamber were shortly compared. The use of a multi-parametric fitting reduced the total uncertainty of CO2 concentration measurements by 62 % compared with one where only a simple CO2 calibration was applied, and by a 90 % when compared to uncertainty declared by the manufacturer. The new SS-TF system allows continuous measurement of CO2 fluxes and CO2 ambient air with low cost (~1.2 k€), low energy demand (< 5 W) and low maintenance (twice per year due to sensor calibration requirements).