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    Rights statement: 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

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    Embargo ends: 12/11/21

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

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Mobile methane measurements : Effects of instrument specifications on data interpretation, reproducibility, and isotopic precision. / Takriti, M.; Wynn, P.M.; Elias, D.M.O.; Ward, S.E.; Oakley, S.; McNamara, N.P.

In: Atmospheric Environment, Vol. 246, 118067, 01.02.2021.

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@article{3260507cf4814e17b6e16dcfddb58a6d,
title = "Mobile methane measurements: Effects of instrument specifications on data interpretation, reproducibility, and isotopic precision",
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. ",
keywords = "Cavity ring-down spectroscopy, Fugitive emissions, Greenhouse gases, Natural gas, Importance sampling, Methane, Sensitivity analysis, Surveys, Concentration Measurement, Concentration ranges, Instrument response time, Isotopic measurement, Measurement conditions, Mobile measurements, Sampling strategies, Stable isotope ratios, Isotopes",
author = "M. Takriti and P.M. Wynn and D.M.O. Elias and S.E. Ward and S. Oakley and N.P. McNamara",
note = "This is the author{\textquoteright}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",
year = "2021",
month = feb,
day = "1",
doi = "10.1016/j.atmosenv.2020.118067",
language = "English",
volume = "246",
journal = "Atmospheric Environment",
issn = "1352-2310",
publisher = "PERGAMON-ELSEVIER SCIENCE LTD",

}

RIS

TY - JOUR

T1 - Mobile methane measurements

T2 - Effects of instrument specifications on data interpretation, reproducibility, and isotopic precision

AU - Takriti, M.

AU - Wynn, P.M.

AU - Elias, D.M.O.

AU - Ward, S.E.

AU - Oakley, S.

AU - McNamara, N.P.

N1 - 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

PY - 2021/2/1

Y1 - 2021/2/1

N2 - 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.

AB - 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.

KW - Cavity ring-down spectroscopy

KW - Fugitive emissions

KW - Greenhouse gases

KW - Natural gas

KW - Importance sampling

KW - Methane

KW - Sensitivity analysis

KW - Surveys

KW - Concentration Measurement

KW - Concentration ranges

KW - Instrument response time

KW - Isotopic measurement

KW - Measurement conditions

KW - Mobile measurements

KW - Sampling strategies

KW - Stable isotope ratios

KW - Isotopes

U2 - 10.1016/j.atmosenv.2020.118067

DO - 10.1016/j.atmosenv.2020.118067

M3 - Journal article

VL - 246

JO - Atmospheric Environment

JF - Atmospheric Environment

SN - 1352-2310

M1 - 118067

ER -