Abstract
The United States Environmental Protection Agency (USEPA) has proposed a method that will be used to quantify fugitive emissions from large area sources such as landfills. The method is presented in the USEPA’s Other Test Method-10 (OTM-10) manual. The method utilizes non-intersecting multiple-beam paths, scanning equipment, and Optical Remote Sensing (ORS) instruments in a variety of radial configurations. The use of an ORS instrument to scan in a radial configuration introduces radial plume mapping (RPM) to the OTM-10. There are several RPM methods discussed in the OTM-10, such as horizontal radial plume mapping (HRPM), vertical radial plume mapping (VRPM), and 1-D radial plume mapping (1D-RPM). The VRPM is the only method discussed in the OTM-10 that is capable computing pollutant flow rates for a large area source such as a landfill, so this study looks into the reliability of the VRPM’s ability to quantify methane emissions from a landfill setting. The VRPM is used as a tool to quantify pollutant concentrations measured in the vertical plane downwind from the emissions source. In conjunction with the concentration data, which is computed by the vertical plane, wind speed and direction data is monitored to convert pollutant concentration values to pollutant flow rates by multiplying the concentration data to a trigonometric function of the wind speed.
The objective of this study was to investigate uncertainties associated with the use of the VRPM method in a landfill setting. Once deficiencies in the method are found, users of the VRPM in a landfill setting will be provided with accurate guidelines on the reliability of the method under a variety of conditions. Several uncertainties associated with the VRPM method in a landfill setting include; the location of hot spots in comparison to vertical plane location, the reliability of the of the optimization algorithm used in quantification to correctly compute emission concentration when multiple hot spots are present, and the area contributing to flux (ACF). Through this study it was found that the spatial variability of emissions in the emitting domain can lead to uncertainties of -34 to 190% in the measured flux value when idealistic scenarios were simulated. The level of uncertainty can be reduced by improving the vertical planes location in comparison to the hot spots. The variability in wind direction during VRPM testing can introduce an uncertainty of 20% of the measured flux value. This study also provides an estimate to the ACF for each meteorological stability class defined in the field and has an
uncertainty of 10 to 30% associated with it.
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