Title: Measuring gas emissions from animal waste lagoons with an inverse-dispersion technique Authors
Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2012
Publication Date: January 5, 2013
Citation: Ro, K.S., Johnson, M.H., Stone, K.C., Hunt, P.G., Flesch, T., Todd, R.W. 2013. Measuring gas emissions from animal waste lagoons with an inverse-dispersion technique. Atmospheric Environment. 66:101-106. Interpretive Summary: Measuring gas emissions from animal waste treatment lagoons is very important. Yet, the lagoons are typically located in non-ideal locations surrounded by trees and crops. These settings are not desirable for existing micrometeorological gas measuring techniques. This study investigated the accuracy of the inverse-dispersion technique for measuring gas emissions from waste lagoons. It used a fabricated emission source floating on a lagoon. The inverse-dispersion technique was evaluated during spring, summer, and fall seasons. Although a lagoon environment is challenging and clearly violates some of the assumptions made in the technique development, our results had an accuracy level of 88%. This was similar to desired results found in much more ideal environments. This suggests that the inverse-dispersion technique is very robust even in non-ideal settings. It is particularly encouraging for researchers and regulatory agencies studying gas emissions from lagoons. The inverse-dispersion technique presents a simple and economical measurement tool for these challenging environments.
Technical Abstract: Measuring gas emissions from treatment lagoons and storage ponds poses challenging conditions for existing micrometeorological techniques due to non-ideal conditions such as trees and crops surrounding the lagoons, and short fetch to establish equilibrated microclimate conditions within the water boundary. This study evaluated the accuracy of an emerging backward Lagrangian stochastic (bLS) inverse-dispersion technique to measure gas emissions from lagoons. It used a fabricated floating emission source with known emission rates from an irrigation lagoon that resembled typical treatment lagoon environments. The measured parameters were wind statistics via 3-dimensional anemometers and downwind path-integrated concentrations. The anemometers were located either on the upwind, downwind, or side berm parallel to wind. Additionally, the berm surface was deliberately roughened during the summer by placing pine straw bales along the berms to simulate vegetation growth. Regardless of the surface roughness, using an anemometer located on the upwind berm produced the most accurate results (0.93 ± 0.19) when its fetch (i.e., corn field) was clear and uniform during spring and fall. However, during the summer, the adjacent corn crop grew more than 2 m high, and the anemometer had to be moved to the side berm. Yet this resulted in a decrease in accuracy to only 0.81 ± 0.18. Thus, even with less than idealized conditions, the bLS inverse-dispersion technique still produced reasonably accurate emission rates. This demonstrated the robustness of this easy-to-use bLS inverse-dispersion technique for complex agricultural emission measurements.