Metrology for low-cost CO 2 sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO 2 fluxes observations

<p>Soil CO<span class="inline-formula">₂</span> 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<span class="inline-formula">₂</span> flux measurements from soil could help reduce uncertainty in the global carbon budgets.</p> <p>In the present study, the design, assembly, and calibration of low-cost air enquirer kits, including CO<span class="inline-formula">₂</span> and environmental parameters sensors, is presented. Different types of calibrations for the CO<span class="inline-formula">₂</span> 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<span class="inline-formula">₂</span> fluxes in soil and CO<span class="inline-formula">₂</span> 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<span class="inline-formula">₂</span> values and of the following calculated CO<span class="inline-formula">₂</span> fluxes based on SS-TF. CO<span class="inline-formula">₂</span> 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.</p> <p>The use of a multiparametric fitting reduced the total uncertainty of the CO<span class="inline-formula">₂</span> concentration measurements by 62 %, compared with the uncertainty that occurred when a simple CO<span class="inline-formula">₂</span> 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<span class="inline-formula">₂</span> fluxes and CO<span class="inline-formula">₂</span> ambient air with low cost (EUR <span class="inline-formula">∼1200</span>), low energy demand (<span class="inline-formula">&lt;5</span> W), and low maintenance (twice per year due to sensor calibration requirements).</p>

Abstract licence: CC BY

A person counts once a day per paper. We keep no cookie and no address: a reader is a hash that changes every day. Any month under five reads shows no number.