A simple diffusion model for calculating concentrations from line sources in Nairobi

Abstract

A simple physically realistic model is used for estimating carbon monoxide(CO) from highway in Nairobi using motor vehicle data for 1989. The year 1989 was chosen because it was the most recent year with motor vehicle count data for majority of the streets. Data for 1988 was also sought for comparison purposes. Average motor vehicles speeds in Nairobi were measured for a period of two months using Range master, which uses the ''Doppler effect'' principle. The speeds were used to determine the sources strength or these streets. A simple diffusion equation was then used to estimate concentration of CO at various distances downwind of the streets. The meteorological data used was from previous studies in Nairobi. Streets on which trafffic was slow constituted strong sources strength for carbon monoxide. Concentration was found to be a strong function of distance from the source and depended on wind speed. The pick traffic hours in Nairobi city were noted to be between 7 a.m. and 9 a.m. in the morning and 4 p.m. to 7 p.m. in the evening on most streets. A smaller traffic volum was also observed during lunch hours