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

Abstract

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.

Full-Scale Investigation of Methane and Ammonia Mitigation by Early Single-Dose Slurry Storage Acidification

“…The overall uncertainty of the emissions estimated with the bLS model is complex to evaluate due to the uncertainties of the model itself, the concentration measurements, and the wind statistics. However, the bLS model has been proved to be an acceptable method with relatively small uncertainty (∼10%) (Harper et al and Lemes et al) and good recovery in controlled release experiments. ,− …”

“…The inlets consist of critical orifices (0.25 mm ID polyetheretherketone (PEEK)) that ensure uniform flow at each point. Lemes et al 30 presented the sampling line system in detail. One of the lines (line 1) was connected to two CRDS instruments, Picarro model G2103 and Picarro model G4301 (Picarro Inc., Santa Clara, CA, USA), to measure NH 3 and CH 4 , respectively.…”

“…The overall uncertainty of the emissions estimated with the bLS model is complex to evaluate due to the uncertainties of the model itself, the concentration measurements, and the wind statistics. However, the bLS model has been proved to be an acceptable method with relatively small uncertainty (∼10%) (Harper et al 34 and Lemes et al 30 ) and good recovery in controlled release experiments. 33,35−38 The Monin−Obukhov similarity theory (MOST) was applied to characterize wind profile, including the friction velocity (u * ), Monin− Obukhov stability length (L), surface roughness length (z 0 ), the standard deviation of the wind components (σ u , σ v , and σ w ) normalized by the friction velocity, and WD in half-hour intervals in the software Matlab (Mathworks Inc., Natick, MA, USA).…”