Determination of lateral dispersion of gaseous traffic emissions in an urban roadway
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Date
2011
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Publisher
University of Dar es Salaam
Abstract
The objective of this study was to model lateral concentration distribution of gaseous pollutant emitted by vehicles in an urban roadway. The General Finite Line Source Model (GFLSM), modified from the one developed by Venkatram and Horst (2006) was used. The modification has been made in the lateral diffusion parameter. The model uses as its inputs emission rates from motor vehicles and wind speed and direction. Wind speeds and directions were measured using anemometer and wind vane, and a Gas analyzer was used to measure the concentration distribution of CO and NOx in the study area. Calculated and measured CO and NOx concentration at three locations from the road side were compared. Measurements were made at distances 5 m, 20 m and 30 m from the roadside. Analysis of the data showed that the percentage difference between measured and predicted concentration was 26%, 33% and 49% at distances 5 m, 20 m and 30 m respectively for CO, and that of NOx was 13% and 27% at 5 m and 20 m respectively, from the roadside. The average index of agreement, i, indicated that the model prediction at 5 m from the roadside was good (i = 0.82 and i = 0.83) and decreases with increasing distance from the roadside i.e. at 20 m (i = 0.51 and i = 0.39) for CO and NOx respectively. The under predictions of the model was attributed mainly to uncertainty of the measured background concentration and emission rates. Further studies are recommended, particularly on determining background concentration and source emission rates.
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Available in print
Keywords
Air, Pollution, Gases, Traffic emission
Citation
Ferdinand, S. (2011) Determination of lateral dispersion of gaseous traffic emissions in an urban roadway