Determination of road traffic emissions from lidar data

Road transport is recognized as the major anthropogenic pollution source in urban areas worldwide. To predict the impact of emissions from automobiles on ambient air quality, different mathematical models have been developed, primarily based on the Gaussian plume equation. However there are few field data sets that could be used to evaluate these models. The lidar (Light Detection and Ranging) technique has been used to determine relative particle concentration over the streets of Iowa City, Iowa in December 2001. An important input to diffusion models is the emission rate of pollutants to the atmosphere, the so called emission inventory. Due to insufficient direct emission measurements, emission rates are usually estimated from mass balance calculations. A method has been developed for indirect determination of emission rates, mean wind speed and vertical diffusivity by inversion of the Gaussian model for diffusion from a line-source. To solve the inversion problem, a Newton-Raphson method has been used.