Metrology for low-cost CO2 sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO2 fluxes observations.

Soil CO 2 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 CO 2 flux measurements from soil could help reduce uncertainty in the global carbon budgets. In the present study, the design, assembly, and calibration of low-cost air enquirer kits, including CO 2 and environmental parameters sensors, is presented. Different types of calibrations for the CO 2 sensors and their associated errors are calculated. In addition, for the first time, this type of sensor has been applied to design, develop, and test a new steady-state through-flow (SS-TF) chamber for simultaneous measurements of CO 2 fluxes in soil and CO 2 concentrations in air. The sensors' responses were corrected for temperature, relative humidity, and pressure conditions in order to reduce the uncertainty in the measured CO 2 values and of the following calculated CO 2 fluxes based on SS-TF. CO 2 soil fluxes measured by the proposed SS-TF and by a standard closed non-steady-state non-through-flow (NSS-NTF) chamber were briefly compared to ensure the reliability of the results. The use of a multiparametric fitting reduced the total uncertainty of the CO 2 concentration measurements by 62 %, compared with the uncertainty that occurred when a simple CO 2 calibration was applied, and by 90 %, when compared to the uncertainty declared by the manufacturer. The new SS-TF system allows the continuous measurement of CO 2 fluxes and CO 2 ambient air with low cost (EUR ∼1200), low energy demand (<5 W), and low maintenance (twice per year due to sensor calibration requirements). [ABSTRACT FROM AUTHOR]