Quantifying methane emission from fugitive sources by combining tracer release and downwind measurements - a sensitivity analysis based on multiple field surveys.
Using a dual species methane/acetylene instrument based on cavity ring down spectroscopy (CRDS), the dynamic plume tracer dispersion method for quantifying the emission rate of methane was successfully tested in four measurement campaigns: (1) controlled methane and trace gas release with different trace gas configurations, (2) landfill with unknown emission source locations, (3) landfill with closely located emission sources, and (4) comparing with an Fourier transform infrared spectroscopy (FTIR) instrument using multiple trace gasses for source separation. The new real-time, high precision instrument can measure methane plumes more than 1.2 km away from small sources (about 5 kg h(-1)) in urban areas with a measurement frequency allowing plume crossing at normal driving speed. The method can be used for quantification of total methane emissions from diffuse area sources down to 1 kg per hour and can be used to quantify individual sources with the right choice of wind direction and road distance. The placement of the trace gas is important for obtaining correct quantification and uncertainty of up to 36% can be incurred when the trace gas is not co-located with the methane source. Measurements made at greater distances are less sensitive to errors in trace gas placement and model calculations showed an uncertainty of less than 5% in both urban and open-country for placing the trace gas 100 m from the source, when measurements were done more than 3 km away. Using the ratio of the integrated plume concentrations of tracer gas and methane gives the most reliable results for measurements at various distances to the source, compared to the ratio of the highest concentration in the plume, the direct concentration ratio and using a Gaussian plume model. Under suitable weather and road conditions, the CRDS system can quantify the emission from different sources located close to each other using only one kind of trace gas due to the high time resolution, while the FTIR system can measure multiple trace gasses but with a lower time resolution.
Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark. Electronic address: jagm@env.dtu.dk.
Jacob G
JG
Mønster
Chalmers University of Technology/FluxSense AB, SE-41296 Göteborg, Sweden.
Jerker
J
Samuelsson
Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Peter
P
Kjeldsen
Picarro Inc., Santa Clara, CA, USA.
Chris W
CW
Rella
Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Charlotte
C
Scheutz
D000114:Acetylene / Q000737:chemistry*; D000393:Air Pollutants / Q000032:analysis*; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods*; D005740:Gases; D005843:Geography; D008697:Methane / Q000032:analysis*; D016011:Normal Distribution; D012037:Refuse Disposal / Q000379:methods*; D015203:Reproducibility of Results; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D064091:Waste Disposal Facilities; D014887:Weather; D014919:Wind
D000393:Air Pollutants; D005740:Gases; D000114:Acetylene; D008697:Methane
Greenhouse gases; Tracer dispersion method; Whole landfill emission measurement