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Open AccessCommunication

Assessment of Open-path Spectrometer Accuracy at Low Path-integrated Methane Concentrations

1
Former Graduate Student at School of Environmental Sciences, University of Guelph, 50 Stone Road E, Guelph, ON N1G2W1, Canada
2
School of Environmental Sciences, University of Guelph, 50 Stone Road E, Guelph, ON N1G2W1, Canada
3
Ottawa Research and Development Centre, Science and Technology Branch, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON K1A0C6, Canada
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(2), 184; https://doi.org/10.3390/atmos11020184
Received: 19 December 2019 / Revised: 1 February 2020 / Accepted: 4 February 2020 / Published: 10 February 2020
(This article belongs to the Special Issue 10th Anniversary of Atmosphere: Air Quality)
The accurate measurement of greenhouse gas emissions is a challenge for atmospheric science. Long-range open-path sensors are flexible enough to be applied to a variety of complex emission sources, and single devices are often used to measure both high and low path-integrated concentrations. As this technology develops, it is important to examine potential sources of inaccuracy. A GasFinder3 open-path laser was tested with a range of path-integrated concentrations from 11.7 to 182 ppm∙m CH4 using certified standard gases. The measured path-integrated concentrations had a positive bias which was higher than 10% at low path-integrated concentrations (<50 ppm∙m) with a declining trend expected to be under 2% at 200 ppm∙m. A linear equation was used to correct the measured path-integrated concentrations to fit the expected values. After correction, the average bias was reduced to −0.36% and there was no relationship with path-integrated concentration. A relative bias less than ±3% was achieved above ca. 150 ppm∙m with or without calibration. Measurement campaigns may reduce error by increasing path lengths to maximize path-integrated concentration. When low path-integrated concentrations are expected, calibration over the expected range is beneficial. View Full-Text
Keywords: open-path laser; methane; path-integrated concentration; GasFinder3 open-path laser; methane; path-integrated concentration; GasFinder3
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MDPI and ACS Style

DeBruyn, Z.J.; Wagner-Riddle, C.; VanderZaag, A. Assessment of Open-path Spectrometer Accuracy at Low Path-integrated Methane Concentrations. Atmosphere 2020, 11, 184.

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