On estimating emissions through horizontal fluxes

This paper examines a popular method of estimating emissions from fugitive sources, which consists of computing horizontal fluxes using measured vertical profiles of velocities and concentrations at several locations downwind of a source. The horizontal flux is the height integral of the product of the velocity normal to the source and the concentration. If the losses between the source and the measurement location are small, the emission rate per unit length of the source is the horizontal flux. The calculation of horizontal flux is not straightforward because we need to make assumptions about the behavior of the concentration profile; the concentration measurements only suggest a plausible profile. We show that this uncertainty in the calculation can be reduced by using a dispersion model to interpret the data. We then provide a quantitative basis for the discussion by comparing horizontal flux calculations presented by Veranth et al. (Atmospheric Environment 37 (2003) 2295) with emissions inferred from a dispersion model applied to the same data set.