22 Sep 2022
22 Sep 2022
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Evaluation of open and closed path sampling systems for determination of emission rates of NH3 and CH4 with inverse dispersion modelling

Yolanda Maria Lemes1, Christoph Häni2, Jesper Nørlem Kamp1, and Anders Feilberg1 Yolanda Maria Lemes et al.
  • 1Department of Engineering, Aarhus University, Gustav Wieds Vej 10D, 8000 Aarhus, Denmark
  • 2School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Länggasse 85, 3052 Zollikofen, Switzerland

Abstract. The gas emission rates of ammonia (NH3) and methane (CH4) from an artificial source covering a surface area of 254 m2 were determined by inverse dispersion modelling (IDM) from point and line-integrated concentration measurements with closed and open-path analyzers. Eight controlled release experiments were conducted with different release rates ranging from 3.8 ± 0.21 to 17.4 ± 0.4 mg s-1 and from 30.7 ± 1.4 to 142.8 ± 2.9 mg s-1 for NH3 and CH4, respectively. The distance between the source and concentration measurement positions ranged from 15 m to 60 m. Our study consisted of more than 200 fluxes averaged intervals of 10 min or 15 min. The different releases cover a range of different climate conditions: cold (< 5 °C), temperate (< 13 °C) and warm (< 18 °C). As the average of all releases with all instrument types, the CH4 recovery rate QbLS/Q was 0.95 ± 0.08 (n = 19). There was much more variation in the recovery of NH3, with an average of 0.66 ± 0.15 (n = 10) for all the releases with the line-integrated system. However, with an improved sampling line placed close to the source an average recovery rate of 0.82 ± 0.05 (n = 3) was obtained for NH3. Under comparable conditions, the recovery rate obtained with an open-path analyzer was 0.91 ± 0.07 (n = 3). The effects of measurement distance, physical properties of the sampling line, and deposition are discussed.

Yolanda Maria Lemes et al.

Status: open (until 01 Nov 2022)

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Yolanda Maria Lemes et al.

Yolanda Maria Lemes et al.


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Short summary
The implementation of the new method, line-average concentration measurement with a closed-path analyzer, will enable measurement of fluxes of multiple gases from different types of sources and evaluate the effects of mitigation strategies on emissions. In addition, this method allows for continuous online measurements that resolve temporal variation in ammonia emissions and the peak emissions of methane.