ARS | Publication request: Greenhouse gas source identification and flux measurements using an optical remote sensing method and a photoacoustic multi-gas analyzer

Submitted to: USDA Greenhouse Gas Symposium
Publication Type: Abstract Only
Publication Acceptance Date: December 11, 2006
Publication Date: February 5, 2007
Citation: Ro, K.S., Johnson, M.H., Novak, J.M., Frederick, J.R., Watts, D.W. 2007. Greenhouse gas source identification and flux measurements using an optical remote sensing method and a photoacoustic multi-gas analyzer. Proceedings of 4th USDA Greenhouse Gas Conference, February 6-8, 2007, Baltimore, Maryland. CDROM

Technical Abstract: Soil properties such as particle size, soil organic carbon (SOC) and moisture contents, tillage operations and crop management practices influence greenhouse gas emission or consumption patterns from agricultural lands. Greenhouse gas (GG) emissions have been measured on small field plots, although minimal information is available on a landscape-scale. The objective of this research was to identify special differences of GG emissions and measure their fluxes from two 3.5-ha fields. The fields contain both well-drained upland and poorly-drained depressional soils in the middle Coastal Plain region of South Carolina. An optical remote sensing (ORS) technique was used to identify the regions of high GG emissions. The ORS system included open-path tunable diode lasers for CH4 and CO2 gas measurements, controlled by an automatic positioning device, to receive laser reflections from nine retroreflectors. The ORS system measured path-integrated concentrations (PICs) of the test fields, which were then used to generate concentration contour diagrams via new horizontal radial plum mapping (HRPM) computer algorithms. For ground truthing, fluxes of GG (i.e., CO2, CH4, and N2O) from multiple points across the test fields were also measured using a static flux chamber and a photoacoustic multigas analyzer. Sulfur hexafluoride was injected to estimate ventilation rate of the static chamber. Contour diagrams of the GG fluxes were generated and were compared with the contours of SOC and moisture contents. The effects of rainfalls and different tillage operations (both conservation and conventional) on the GG flux were also studied.