ATMOSPHERIC STABILITY AND SENSITIVITY ANALYSIS OF GAUSSIAN PLUME DISPERSION

Abstract

Air pollution is one of the major environmental challenges. It is generally measured in terms of mass or volume of the pollutants present in unit volume of air. Air quality models are designed to characterize primary pollutants that are emitted directly into the atmosphere. These models are widely used by regulatory authorities tasked with controlling air pollution. Air quality models use mathematical and numerical techniques to simulate the physical and chemical processes that affect air pollutants as they disperse and react in the atmosphere. Wind speed and environmental lapse rates directly influence the dispersion pattern. In the present work an investigation is done on various stability classes along with the forces acting on air parcel in the atmosphere, in order to understand the conditions for achieving maximum dispersion of pollutants. Stability in the atmosphere is usually described in terms of lapse rates. The most widely used model for estimating the ground level concentration is Gaussian Plume Model, Most USEPA dispersion models used in regulatory application are of the Gaussian type. Gaussian distribution implies that the pollutant concentration profile forms a bell-shaped curve centered about the plume centerline in both the horizontal and the vertical direction. The Gaussian plume models are sensitive to the input parameters. Selection of dispersion coefficients or sigma schemes is one of them. The present work deals with the sensitivity analysis of Gaussian plume model with two, widely used, dispersion coefficients or `sigmas', the horizontal dispersion coefficients and vertical dispersion coefficient. The ground level concentrations of two cases, one for open country conditions and other for urban conditions are analyzed for various sigma schemes and for each stability class. A MATLAB program is prepared for steady-state Gaussian distribution model of a single, continuous point source for its various conditions. i