Mobile methane measurements : Effects of instrument specifications on data interpretation, reproducibility, and isotopic precision

Takriti, M. and Wynn, P.M. and Elias, D.M.O. and Ward, S.E. and Oakley, S. and McNamara, N.P. (2021) Mobile methane measurements : Effects of instrument specifications on data interpretation, reproducibility, and isotopic precision. Atmospheric Environment, 246: 118067. ISSN 1352-2310

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Abstract

Recent research has used mobile methane (CH4) measurements to identify and quantify emissions, but the effect of instrument response time on concentration measurements is rarely considered. Furthermore, stable isotope ratios are increasingly used in mobile measurements to attribute sources, but the precision of mobile isotopic measurements depend on a combination of instrument and measurement conditions. Here we tested the effect of instrument speed on concentration measurements by outfitting a vehicle with isotopic and concentration-only gas analysers with different response times and conducting multiple mobile surveys. Additionally, we performed a sensitivity analysis for the isotopic precision achievable under different conditions by programming a physical model, validated with empirical data from our mobile surveys. We found that slower response time led to a greater underestimation of measured CH4 concentration, during both driving and stationary measurements, while the area under peaks in concentration is consistent and provides a robust means of comparing data between instruments. We also explore the use of an algorithm to improve instrument response. Our sensitivity analysis showed that the precision of isotopic measurements increases with the concentration range and the duration of the measurement following a power law. Our findings have important implications for the reporting and comparability of results between surveys with different instrumental setups and provide a framework for optimising sampling strategies under given objectives, conditions, and instrument capabilities.

Item Type:

Journal Article

Journal or Publication Title:

Atmospheric Environment

Additional Information:

This is the author’s version of a work that was accepted for publication in Atmospheric Environment. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Atmospheric Environment, 246, 2021 DOI: 10.1016/j.atmosenv.2020.118067

Uncontrolled Keywords:

/dk/atira/pure/subjectarea/asjc/2300/2300

Subjects:

?? cavity ring-down spectroscopyfugitive emissionsgreenhouse gasesnatural gasimportance samplingmethanesensitivity analysissurveysconcentration measurementconcentration rangesinstrument response timeisotopic measurementmeasurement conditionsmobile measuremen ??

Departments:

Faculty of Science and Technology > Lancaster Environment Centre

ID Code:

151424

Deposited By:

ep_importer_pure

Deposited On:

05 Feb 2021 12:05

Refereed?:

Yes

Published?:

Published