Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/12/2011
Publication Date: 8/28/2011
Citation: Ro, K.S., Johnson, M.H., Hunt, P.G., Flesch, T. 2011. Comparing two micrometeorological techniques for estimating trace gas emissions from distributed sources [abstract]. American Chemical Society National Meeting and Exposition, August 28-September 1, 2011, Denver, Colorado.
Technical Abstract: Measuring trace gas emission from distributed sources such as treatment lagoons, treatment wetlands, land spread of manure, and feedlots requires micrometeorological methods. In this study, we tested the accuracy of two relatively new micrometeorological techniques, vertical radial plume mapping (VRPM) and backward Lagrangian stochastic (bLs) techniques. These techniques were combined with a path integrated optical remote sensing (PI-ORS) system consisting of a tunable diode absorption spectrometer mounted on an automatic positioning device. Integrated VRPM software (Arcadis Inc., North Carolina) controls the automatic positioning device to direct the laser beams to various retroreflectors on the ground and the tower. WindTrax software (Thunder Beach Scientific, Nanaimo, Canada) interfaces concentration and wind sensor data with the bLs dispersion model. Three different distributed emission sources were simulated; 3.1m and 27m squares of perforated PVC pipe networks, and soaker hoses stretching out to make a star-shaped circular emission source with diameter of 40m. Known rates of the CH4 gas were released during the validation studies. The actual masses of CH4 gas released were measured with a floor scale periodically. For single source emissions, the VRPM method measured CH4 emission rate at QVRPM/Q = 1.38 ± 0.28; the bLs method measured emission rate at QbLs/Q = 0.98 ± 0.24. The accuracy of the bLs technique improved with number of path integrated concentration (PIC) data. For double emission sources, the accuracy of the VRPM method decreased significantly (QVRPM/Q = 1.76 ± 0.28). The accuracy of bLs method decreased slightly for the double emission sources (QbLs/Q = 0.93 ± 0.23). The impact of number PICs and footprint on accuracy of these two techniques will also be discussed at the meeting.