Calibration and field testing of cavity ring-down laser spectrometers measuring CH4, CO2, and δ13CH4 deployed on towers in the Marcellus Shale region

Natasha Lynn Miles, Douglas K. Martins, Scott James Richardson, Christopher W. Rella, Caleb Arata, Thomas Claude Yves Lauvaux, Kenneth James Davis, Zachary Robert Barkley, Kathryn McKain, Colm Sweeney

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Abstract

Four in situ cavity ring-down spectrometers (G2132-i, Picarro, Inc.) measuring methane dry mole fraction (CH4/, carbon dioxide dry mole fraction (CO2/, and the isotopic ratio of methane (δ13CH4/ were deployed at four towers in the Marcellus Shale natural gas extraction region of Pennsylvania. In this paper, we describe laboratory and field calibration of the analyzers for tower-based applications and characterize their performance in the field for the period January-December 2016. Prior to deployment, each analyzer was tested using bottles with various isotopic ratios, from biogenic to thermogenic source values, which were diluted to varying degrees in zero air, and an initial calibration was performed. Furthermore, at each tower location, three field tanks were employed, from ambient to high mole fractions, with various isotopic ratios. Two of these tanks were used to adjust the calibration of the analyzers on a daily basis. We also corrected for the cross-interference from ethane on the isotopic ratio of methane. Using an independent field tank for evaluation, the standard deviation of 4 h means of the isotopic ratio of methane difference from the known value was found to be 0.26% δ13CH4. Following improvements in the field tank testing scheme, the standard deviation of 4 h means was 0.11 %, well within the target compatibility of 0.2 %. Round-robin style testing using tanks with near-ambient isotopic ratios indicated mean errors of -0.14 to 0.03‰ for each of the analyzers. Flask to in situ comparisons showed mean differences over the year of 0.02 and 0.08 %, for the east and south towers, respectively. Regional sources in this region were difficult to differentiate from strong perturbations in the background. During the afternoon hours, the median differences of the isotopic ratio measured at three of the towers, compared to the background tower, were -0.15 to 0.12‰ with standard deviations of the 10 min isotopic ratio differences of 0.8 %. In terms of source attribution, analyzer compatibility of 0.2% δ13CH4 affords the ability to distinguish a 50 ppb CH4 peak from a biogenic source (at -60 %, for example) from one originating from a thermogenic source (-35 %), with the exact value dependent upon the source isotopic ratios. Using a Keeling plot approach for the non-afternoon data at a tower in the center of the study region, we determined the source isotopic signature to be -31.2-1.9 %, within the wide range of values consistent with a deep-layer Marcellus natural gas source.

Original languageEnglish (US)
Pages (from-to)1273-1295
Number of pages23
JournalAtmospheric Measurement Techniques
Volume11
Issue number3
DOIs
StatePublished - Mar 5 2018

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isotopic ratio
shale
cavity
spectrometer
laser
calibration
methane
measuring
ethane
natural gas
carbon dioxide
perturbation
air

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

@article{d2f717a6c38645ac97d28bcfa8901827,
title = "Calibration and field testing of cavity ring-down laser spectrometers measuring CH4, CO2, and δ13CH4 deployed on towers in the Marcellus Shale region",
abstract = "Four in situ cavity ring-down spectrometers (G2132-i, Picarro, Inc.) measuring methane dry mole fraction (CH4/, carbon dioxide dry mole fraction (CO2/, and the isotopic ratio of methane (δ13CH4/ were deployed at four towers in the Marcellus Shale natural gas extraction region of Pennsylvania. In this paper, we describe laboratory and field calibration of the analyzers for tower-based applications and characterize their performance in the field for the period January-December 2016. Prior to deployment, each analyzer was tested using bottles with various isotopic ratios, from biogenic to thermogenic source values, which were diluted to varying degrees in zero air, and an initial calibration was performed. Furthermore, at each tower location, three field tanks were employed, from ambient to high mole fractions, with various isotopic ratios. Two of these tanks were used to adjust the calibration of the analyzers on a daily basis. We also corrected for the cross-interference from ethane on the isotopic ratio of methane. Using an independent field tank for evaluation, the standard deviation of 4 h means of the isotopic ratio of methane difference from the known value was found to be 0.26{\%} δ13CH4. Following improvements in the field tank testing scheme, the standard deviation of 4 h means was 0.11 {\%}, well within the target compatibility of 0.2 {\%}. Round-robin style testing using tanks with near-ambient isotopic ratios indicated mean errors of -0.14 to 0.03‰ for each of the analyzers. Flask to in situ comparisons showed mean differences over the year of 0.02 and 0.08 {\%}, for the east and south towers, respectively. Regional sources in this region were difficult to differentiate from strong perturbations in the background. During the afternoon hours, the median differences of the isotopic ratio measured at three of the towers, compared to the background tower, were -0.15 to 0.12‰ with standard deviations of the 10 min isotopic ratio differences of 0.8 {\%}. In terms of source attribution, analyzer compatibility of 0.2{\%} δ13CH4 affords the ability to distinguish a 50 ppb CH4 peak from a biogenic source (at -60 {\%}, for example) from one originating from a thermogenic source (-35 {\%}), with the exact value dependent upon the source isotopic ratios. Using a Keeling plot approach for the non-afternoon data at a tower in the center of the study region, we determined the source isotopic signature to be -31.2-1.9 {\%}, within the wide range of values consistent with a deep-layer Marcellus natural gas source.",
author = "Miles, {Natasha Lynn} and Martins, {Douglas K.} and Richardson, {Scott James} and Rella, {Christopher W.} and Caleb Arata and Lauvaux, {Thomas Claude Yves} and Davis, {Kenneth James} and Barkley, {Zachary Robert} and Kathryn McKain and Colm Sweeney",
year = "2018",
month = "3",
day = "5",
doi = "10.5194/amt-11-1273-2018",
language = "English (US)",
volume = "11",
pages = "1273--1295",
journal = "Atmospheric Measurement Techniques",
issn = "1867-1381",
publisher = "Copernicus Gesellschaft mbH",
number = "3",

}

Calibration and field testing of cavity ring-down laser spectrometers measuring CH4, CO2, and δ13CH4 deployed on towers in the Marcellus Shale region. / Miles, Natasha Lynn; Martins, Douglas K.; Richardson, Scott James; Rella, Christopher W.; Arata, Caleb; Lauvaux, Thomas Claude Yves; Davis, Kenneth James; Barkley, Zachary Robert; McKain, Kathryn; Sweeney, Colm.

In: Atmospheric Measurement Techniques, Vol. 11, No. 3, 05.03.2018, p. 1273-1295.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Calibration and field testing of cavity ring-down laser spectrometers measuring CH4, CO2, and δ13CH4 deployed on towers in the Marcellus Shale region

AU - Miles, Natasha Lynn

AU - Martins, Douglas K.

AU - Richardson, Scott James

AU - Rella, Christopher W.

AU - Arata, Caleb

AU - Lauvaux, Thomas Claude Yves

AU - Davis, Kenneth James

AU - Barkley, Zachary Robert

AU - McKain, Kathryn

AU - Sweeney, Colm

PY - 2018/3/5

Y1 - 2018/3/5

N2 - Four in situ cavity ring-down spectrometers (G2132-i, Picarro, Inc.) measuring methane dry mole fraction (CH4/, carbon dioxide dry mole fraction (CO2/, and the isotopic ratio of methane (δ13CH4/ were deployed at four towers in the Marcellus Shale natural gas extraction region of Pennsylvania. In this paper, we describe laboratory and field calibration of the analyzers for tower-based applications and characterize their performance in the field for the period January-December 2016. Prior to deployment, each analyzer was tested using bottles with various isotopic ratios, from biogenic to thermogenic source values, which were diluted to varying degrees in zero air, and an initial calibration was performed. Furthermore, at each tower location, three field tanks were employed, from ambient to high mole fractions, with various isotopic ratios. Two of these tanks were used to adjust the calibration of the analyzers on a daily basis. We also corrected for the cross-interference from ethane on the isotopic ratio of methane. Using an independent field tank for evaluation, the standard deviation of 4 h means of the isotopic ratio of methane difference from the known value was found to be 0.26% δ13CH4. Following improvements in the field tank testing scheme, the standard deviation of 4 h means was 0.11 %, well within the target compatibility of 0.2 %. Round-robin style testing using tanks with near-ambient isotopic ratios indicated mean errors of -0.14 to 0.03‰ for each of the analyzers. Flask to in situ comparisons showed mean differences over the year of 0.02 and 0.08 %, for the east and south towers, respectively. Regional sources in this region were difficult to differentiate from strong perturbations in the background. During the afternoon hours, the median differences of the isotopic ratio measured at three of the towers, compared to the background tower, were -0.15 to 0.12‰ with standard deviations of the 10 min isotopic ratio differences of 0.8 %. In terms of source attribution, analyzer compatibility of 0.2% δ13CH4 affords the ability to distinguish a 50 ppb CH4 peak from a biogenic source (at -60 %, for example) from one originating from a thermogenic source (-35 %), with the exact value dependent upon the source isotopic ratios. Using a Keeling plot approach for the non-afternoon data at a tower in the center of the study region, we determined the source isotopic signature to be -31.2-1.9 %, within the wide range of values consistent with a deep-layer Marcellus natural gas source.

AB - Four in situ cavity ring-down spectrometers (G2132-i, Picarro, Inc.) measuring methane dry mole fraction (CH4/, carbon dioxide dry mole fraction (CO2/, and the isotopic ratio of methane (δ13CH4/ were deployed at four towers in the Marcellus Shale natural gas extraction region of Pennsylvania. In this paper, we describe laboratory and field calibration of the analyzers for tower-based applications and characterize their performance in the field for the period January-December 2016. Prior to deployment, each analyzer was tested using bottles with various isotopic ratios, from biogenic to thermogenic source values, which were diluted to varying degrees in zero air, and an initial calibration was performed. Furthermore, at each tower location, three field tanks were employed, from ambient to high mole fractions, with various isotopic ratios. Two of these tanks were used to adjust the calibration of the analyzers on a daily basis. We also corrected for the cross-interference from ethane on the isotopic ratio of methane. Using an independent field tank for evaluation, the standard deviation of 4 h means of the isotopic ratio of methane difference from the known value was found to be 0.26% δ13CH4. Following improvements in the field tank testing scheme, the standard deviation of 4 h means was 0.11 %, well within the target compatibility of 0.2 %. Round-robin style testing using tanks with near-ambient isotopic ratios indicated mean errors of -0.14 to 0.03‰ for each of the analyzers. Flask to in situ comparisons showed mean differences over the year of 0.02 and 0.08 %, for the east and south towers, respectively. Regional sources in this region were difficult to differentiate from strong perturbations in the background. During the afternoon hours, the median differences of the isotopic ratio measured at three of the towers, compared to the background tower, were -0.15 to 0.12‰ with standard deviations of the 10 min isotopic ratio differences of 0.8 %. In terms of source attribution, analyzer compatibility of 0.2% δ13CH4 affords the ability to distinguish a 50 ppb CH4 peak from a biogenic source (at -60 %, for example) from one originating from a thermogenic source (-35 %), with the exact value dependent upon the source isotopic ratios. Using a Keeling plot approach for the non-afternoon data at a tower in the center of the study region, we determined the source isotopic signature to be -31.2-1.9 %, within the wide range of values consistent with a deep-layer Marcellus natural gas source.

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