Continuous methane concentration measurements at the Greenland ice sheet–atmosphere interface using a low-cost, low-power metal oxide sensor system

Abstract

Abstract. In this paper, the performance of a low-cost and low-power methane (CH4) sensing system prototype based on a metal oxide sensor (MOS) sensitive to CH4 is tested in a natural CH4-emitting environment at the Greenland ice sheet (GrIS). We investigate if the MOS could be used as a supplementary measurement technique for monitoring CH4 emissions from the GrIS with the scope of setting up a CH4 monitoring network along the GrIS. The performance of the MOS is evaluated on the basis of simultaneous measurements using a cavity ring-down spectroscopy (CRDS) reference instrument for CH4 over a field calibration period of approximately 100 h. Results from the field calibration period show that CH4 concentrations measured with the MOS are in very good agreement with the reference CRDS. The absolute concentration difference between the MOS and the CRDS reference values within the measured concentration range of approximately 2–100 ppm CH4 was generally lower than 5 ppm CH4, while the relative concentration deviations between the MOS and the CRDS were generally below 10 %. The calculated root-mean-square error (RMSE) for the entire field calibration period was 1.69 ppm (n=37 140). The results confirm that low-cost and low-power MOSs can be effectively used for atmospheric CH4 measurements under stable water vapor conditions. The primary scientific importance of the study is that it provides a clear example of how the application of low-cost technology can enhance our future understanding on the climatic feedbacks from the cryosphere to the atmosphere.

Reconstruction of high-frequency methane atmospheric concentration peaks from measurements using metal oxide low-cost sensors

“…A similar approach was employed by (Jørgensen et al, 2020) to compensate for effects of micro turbulent mixing of subglacial air with atmospheric observations. Before applying this temporal smoothing on the CRDS data, we resampled both signals, the reference CRDS and the TGS, from their original time resolutions (1s and 2s, respectively) to a common time resolution of 5s.…”

“…Low cost sensors such as low power metal oxide semiconductor (MOS) sensors for methane are an alternative. Recent studies (Riddick et al, 2020;Casey et al, 2019;Collier-Oxandale et al, 2018;Jørgensen et al, 2020;Rivera Martinez et al, 2021;Eugster et al, 2020) tested the ability of MOS sensors to monitor methane concentrations in natural and controlled conditions and showed a fair agreement between the concentrations derived from the sensors and those from high precision reference instruments. MOS sensors are composed of a semiconducting metal oxide sensing element heated at a temperature between 200 • to 400 • C (Özgür Örnek and Karlik, 2012;Barsan et al, 2007).…”

Determining methane mole fraction at a landfill site using the Figaro Taguchi gas sensor 2611-C00 and wind direction measurements

“…58 For example, several studies have conducted TGS eld characterisations, using a high-precision reference instrument (HPR) for model training and renement. 38,47,48,54,55 Most of these previous studies modelled [ CH 4 ] directly using raw TGS resistance, without deriving a baseline resistance representative of sampling at a xed (predened) reference [CH 4 ] level. The ability to derive a robust baseline TGS resistance at a reference [CH 4 ] level, and from eld sampling, would be a valuable asset in estimating [CH 4 ] at a desired ±1 ppm [CH 4 ] accuracy, by taking the resistance ratio between measured TGS resistance and this reference resistance.…”

“…The ability to derive a robust baseline TGS resistance at a reference [CH 4 ] level, and from eld sampling, would be a valuable asset in estimating [CH 4 ] at a desired ±1 ppm [CH 4 ] accuracy, by taking the resistance ratio between measured TGS resistance and this reference resistance. 31,34,55 Furthermore, using a resistance ratio is recommended by the manufacturer, 39,40 although this fundamental approach is less easy to implement if baseline resistance is inuenced by varying (nongas mole fraction) environmental conditions. 30,31 As far as we are aware only Jørgensen et al 55 successfully derived [CH 4 ] using a baseline resistance during eld sampling (where they set their reference [CH 4 ] level to 0 ppm), although their baseline resistance was assigned a constant value specic to a certain set of environmental conditions.…”

Use of metal oxide semiconductor sensors to measure methane in aquatic ecosystems in the presence of cross‐interfering compounds

“…Continental aquatic ecosystems, especially shallow water bodies (wetlands, ponds, small lakes) are a significant component of the global carbon budget and biogeochemists are starting to implement MOS technology to study methane fluxes at the water-atmosphere interface (Jørgensen et al 2020) using floating flux chambers (Bastviken et al 2020).…”