Submitted to: Atmosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2011
Publication Date: 9/23/2011
Citation: Ro, K.S., Johnson, M.H., Hunt, P.G., Flesch, T.K. 2011. Measuring trace gas emission from multi-distributed sources using vertical radial plume mapping (VRPM) and backward Lagrangian stochastic (bLS) techniques. Atmosphere. 2:553-566.
Interpretive Summary: This study investigates the accuracy of two recently developed micrometeorological techniques in measuring gas emission rate from multiple emission sources. Both techniques utilize line concentration of gas. The vertical radial plume mapping (VRPM) technique was originally developed by the US Environmental Protection Agency in order to measure methane gas emission from closed landfills. The backward Lagrangian stochastic (bLS) technique was developed for idealized conditions where the wind can be adequately described by simple statistical relationships. While some accuracy of these methods in simple situations involving a single emission source was reported in the literature, we were interested in finding out the accuracy of these methods in more complex situations that are often seen in agricultural applications. We tested the accuracy of these techniques measuring emission rates from two distinct area sources located adjacent to one another such as two constructed wetland cells for animal wastewater treatment. We used synthetic area emission sources with known emission rates to compare with the measured emission rates using these techniques. We found that the bLS technique could produce emission rates with higher accuracy than the VRPM technique. In addition, the fewer number of path integrated concentration data required by the bLS technique significantly reduced the effort in setting up of instrumentation.
Technical Abstract: Two micrometeorological techniques for measuring trace gas emission rates from distributed area sources were evaluated using a variety of synthetic area sources. The accuracy of the vertical radial plume mapping (VRPM) and the backward Lagrangian (bLS) techniques with an open-path optical spectroscopic sensor was evaluated for multiple emission source and sensor configurations. The VRPM method yielded relative accuracies as high as 1.38±0.28 for a single area source, while the bLS method resulted in relative accuracies as high as 0.98±0.24. Relative accuracies for dual source emissions for the VRPM and bLS techniques were as high as 1.23±0.17 and 0.98 ±0.33, respectively. Results suggest that the bLS method may provide more accurate greenhouse gas emission rates from multi-distributed sources than the VRPM method. In addition, the bLS technique yield relative accuracy of 1.08 ± 0.44 using multiple point sensors in a horizontal line instead of the open-path optical spectroscopic sensor.