Development of a Line Source Dispersion Model for Gaseous Pollutants by Incorporating Wind Shear near the Ground under Stable Atmospheric Conditions

Abstract

Transportation sources are a major contributor to air pollution in urban areas. The role of air quality modelling is vital in the formulation of air pollution control and management strategies. Many models have appeared in the literature to estimate near-field ground level concentrations from mobile sources moving on a highway. However, current models do not account explicitly for the effect of wind shear (magnitude) near the ground while computing the ground level concentrations near highways from mobile sources. This study presents an analytical model based on the solution of the convective-diffusion equation by incorporating the wind shear near the ground for gaseous pollutants. The model input includes emission rate, wind speed, wind direction, turbulence, and terrain features. The dispersion coefficients are based on the near field parameterization. The sensitivity of the model to compute ground level concentrations for different inputs is presented for three different downwind distances. In general, the model shows Type III sensitivity (i.e. the errors in the input will show a corresponding change in the computed ground level concentrations) for most of the input variables. However, the model equations should be reexamined for three input variables (wind velocity at the reference height and two variables related to the vertical spread of the plume) to make sure that that the model is valid for computing ground level concentrations.

Development of an Analytical Line Source Dispersion Model to Predict Ground Level Concentrations for Particulate Matter (PM) of Different Particle Size Ranges

“…The surprising result is that the variables related to dispersion coefficients show very little sensitivity. This result is different than the one reported by Harsha and Kumar [16,[25][26][27] using the ASTM method and the Sensitivity-Index method. The analysis performed using Crystal Ball should be re-examined.…”

Development and Evaluation of SLINE 1.0, a Line Source Dispersion Model for Gaseous Pollutants by Incorporating Wind Shear Near the Ground under Stable and Unstable Atmospheric Conditions

“…Figure 6 represents the changes in predicted concentration (also called model results) and calibration residuals for all the input variables/parameters. Note that the type of sensitivity (Type I, Type II, Type III, and Type IV) was determined for each variable/parameter depending on changes to the calibration residual values and predicted concentration values by studying the model runs [55,56]. The model runs for SLINE 1.0, varying the input variables/parameters, are plotted in Figure 6.…”