On the estimation of impact of vehicular emissions

Abstract It is suggested a method for estimating the carbon monoxide (CO) concentration levels in various zones of an urban area caused by vehicular emissions. The method is based on using the adjoint operator and adjoint transport equation and can be used by any pollution transport model. It is illustrated here with a simple two-dimensional pollution transport model and its adjoint applied to Guadalajara City. The car emissions are described by linear sources located along the main city roadways. Each of the models is well posed, that is, has unique solution continuously depending on the CO emission rates and initial CO distribution in the area. Two equivalent (direct and adjoint) mean CO concentration estimates in an ecologically important zone are given. The sensitivity of these estimates with respect to vehicular emission rates along the main city roads, as well as to the wind and initial CO distribution is examined. Compatible, balanced, and absolutely stable second-order finite-difference schemes based on the splitting method are used to simulate CO transport in the Guadalajara City Metropolitan Area (GCMA). It is shown that the adjoint model solutions serve as influence (Green) functions providing valuable information on the contribution of various parts of the roadways in polluting the zone selected.