Technical note: Facilitating the use of low-cost methane (ch4) sensors in flux chambers-calibration, data processing, and an open-source make-it-yourself logger

Abstract

A major bottleneck regarding the efforts to better quantify greenhouse gas fluxes, map sources and sinks, and understand flux regulation is the shortage of low-cost and accurate-enough measurement methods. The studies of methane ( CH4)-a long-lived greenhouse gas increasing rapidly but irregularly in the atmosphere for unclear reasons, and with poorly understood source-sink attribution-suffer from such method limitations. This study presents new calibration and data processing approaches for use of a low-cost CH4 sensor in flux chambers. Results show that the change in relative CH4 levels can be determined at rather high accuracy in the 2-700 ppm mole fraction range, with modest efforts of collecting reference samples in situ and without continuous access to expensive reference instruments. This opens possibilities for more affordable and time-effective measurements of CH4 in flux chambers. To facilitate such measurements, we also provide a description for building and using an Arduino logger for CH4, carbon dioxide ( CO2), relative humidity, and temperature.