Kyoung Ro, Melvin Johnson, and Patrick Hunt. USDA-ARS, 2611 West Lucas Street, Florence, SC 29501-1241
The U.S. EPA recently developed an open-path remote sensing method to identify hot spots and estimate fugitive gas emissions from closed landfills. The method measures several path-integrated concentrations (PICs) of gases using open-path optical instruments. These PICs are then processed using a computer algorithm called radial plume mapping method (RPM). Vertical RPM (VRPM) reconstructs vertical plume maps of a vertical plane downwind of an area source based on several PICs measured in the plane. Multiplying the vertical concentration plume map with the wind speeds perpendicular to the vertical plane, the emission rate of the gas could be estimated. This method is listed under the USEPA Technology Transfer Network Emission Measurement Center Category C which may be considered for use in federally enforceable state and local programs once approved by an EPA Regional State Implementation Plans (SIP) process. The objective of this research is to investigate the applicability of this VRPM method for estimating methane emission from agricultural sites. The optical remote sensing (ORM) system consists of an open-path tunable diode laser CH4 gas detector and retroreflectors, computer controlled automatic positioning device for precise scanning of PICs, a portable 10-m weather mast, wind sensors, and a custom designed VRPM software fully integrated to interface with the ORM system components. This method is currently being validated with a distribution source of known emission rates.