Landfill odour: assessment of emissions by the flux footprint method

摘要

This paper will focus on the development of an innovative method for estimating odour fluxes and the contributing source areas from a Municipal Solid Waste (MSW) landfill site. A micrometeorological model has been developed based on the estimation of footprints of scalar odour concentration measurements in the atmospheric surface layer. The model is based on an analytical solution of the Eulerian adyection-diffusion equation for vertical diffusion; model parameters include the location of the odour sensor and standard surface layer scaling factors. Lindvall Hoods are commonly used for measuring odour fluxes from ground based fugitive sources. However these cannot replicate the real atmospheric conditions. Common micrometeorological techniques for determining fluxes, such as vertical gradient measurements or eddy correlation methods, yield a flux magnitude but give practically no information about the source location. On the other hand the flux footprint describes the expansion and contraction of the required fetch under varying atmospheric stabilities. Preliminary results from the model are quite encouraging and agree well with those from Lindvall hood measurements. The accuracy of Lindvall hood measurements depends on how tightly the hood is positioned on the uneven landfill surface. It should prevent any air escaping out from the sides of the hood open to the atmosphere. Typical results show an average odour flux of +-25.91 (ou m~(-2) s~(-1)) from freshly tipped wastes for an upwind fetch of 45.0m and with the sensor at a height of 1.5m from the ground. The hood results have a geometric mean of +-29.35 (ou m~(-2) s~(-1)) based on the inlet air volume and a shade air temperature of 22.5℃.