Dispersion Gaussian plume model

Air Pollution Dispersion Application of air dispersion modeling principles and EPA tools to assessing environmental impacts from stack and area releases of pollutants Dispersion theory Gaussian plume model Ground-level concentrations Worst case scenarios Air quality impact assessments Stationary source emissions... 

The earliest and still widely used dispersion model to compute pollutant concentration profiles is the Gaussian plume model for single or multiple source pollution problems. Box-type model techniques, which can take into account nonlinear interactions among different species arising from chemical reactions, have been used in longer-range dispersion computations. 

The Gaussian Plume Model is the most well-known and simplest scheme to estimate atmospheric dispersion. This is a mathematical model which has been formulated on the assumption that horizontal advection is balanced by vertical and transverse turbulent diffusion and terms arising from creation of depletion of species i by various internal sources or sinks. In the wind-oriented coordinate system, the conservation of species mass equation takes the following form ... 

Software for dispersion modeling uses Gaussian plume model. Phe system calculates concentration or deposition values for inputed time periods. May be used in conjunction with "Breeze Air."... 

The modeling package, delivered to the EPA, includes nationwide data bases for emissions, dispersion meteorology, and population patterns. These data are used as input for a Gaussian plume model for point sources and a box model for urbanwide area sources. Prototype modeling is used for point sources that are too numerous to define individually. Building wake effects and atmospheric chemical decay are addressed. 

Weber, A. H. (1976). Atmospheric Dispersion Parameters in Gaussian Plume Modeling, EPA-600/4-76-030A. U.S. Environ. Prot. Agency, Washington, D.C. 

Pheromone propagation by wind depends on the release rate of the pheromone (or any other odor) and air movements (turbulent dispersion). In wind, the turbulent diffusivity overwhelms the diffusion properties of a volatile compound or mixture itself. Diffusion properties are now properties of wind structure and boundary surfaces, and preferably termed dispersion coefficients. Two models have dominated the discussion of insect pheromone propagation. These are the time-average model (Sutton, 1953) and the Gaussian plume model. 

The Gaussian plume model estimates the average pheromone flux by multiplying the measured odor concentration by mean wind speed, using the following formula (Elkinton etal, 1984). Everything is the same as in the Sutton model, except that ay and az, respectively, replace the terms Cy and Cz of the Sutton model. Dispersion coefficients are determined for each experiment separately. 

One commonly used suite of models that is based on Gaussian plume modeling is the Industrial Source Complex (ISC) Dispersion Models (US EPA, 1995). This suite includes both a short-term model (ISCST), which calculates the hourly air pollutant concentrations in an area surrounding a source, as well as a long-term model (ISCLT), which calculates the average air pollutant concentrations over a year or longer. ISCLT uses meteorological data summarized by frequency for 16 radial sectors (22.5° each) this data format is referred to as a stability array (STAR). Within each sector of STAR, joint frequencies of wind direction, wind speed, and atmospheric stability class are provided. 

Brown, M.J., Arya, S.P., and Snyder, W.H., 1992. Vertical dispersion from surface and elevated releases an investigation of a non-Gaussian plume model, J. Appl. Meteorol., 32, pp. 490-505. 

Sykes, R.L, Lewellen, W.S., and Parker, F.S., 1986. A Gaussian plume model of atmospheric dispersion based on second order closure, J. Climate. Appl. Meteorol. 25, pp. 322-331. 

The Gaussian plume model for atmospheric diffusion has emerged as the most commonly used mathematical technique for dispersion calculations from continuous sources. There are a number of factors in its favor. 

The passive gas dispersion models are usually based on the Gaussian plume model. In Gaussian models, atmospheric dispersion is taken into account through empirical dispersion coefficients that vary by atmospheric turbulence class (stability class) and distance from source. Dilution by the wind is taken into account through division by wind speed. No consideration, however, is given to the difference of the density between the ambient air and the gas, other than to calculate an initial plume rise if the release is hot (buoyant plumes rise according to relatively well-established approximations and then behave as a plume characterized by Gaussian concentration profiles). Because of this, these models must only be used for gas mixtures with a density approximately the same as that of air. 

Our computations are based on the release estimates provided by the authorities (Lithuanian State Committee for Environmental Protection, 1989). We have applied a long-range dispersion model that uses a Gaussian plume model up to a specified transition distance, and... 

Fares et al. (1980) were the first to apply a general Gaussian plume model (3.5) to pheromone dispersion and the first to emphasize the importance of atmospheric stability on pheromone communication. They used dispersion coefficients derived from tracer experiments conducted in a pine forest. They hypothesized that the diurnal pattern of bark beetle responses to pheromone may relate to diurnal changes in stability. (For further discussion of the selective forces influencing diurnal activity patterns see Card6 and Baker, Chapter 12.)... 

Elkinton et al. (1984) used probit analysis to test the predictions of the Gaussian plume model using the dispersion coefficients suggested by Pasquill... 

Fig. 3.2 Predicted concentration isopleths of airborne material utilizing the Gaussian plume model and the Pasquill Prairie Grass dispersion coefficients versus the occurrence of male gypsy moth wing-fanning behavior over a 10-minute interval following pheromone release from a point source. The 1 x 10" isopleth approximates the minimum concentration that produces a similar wing-fanning response in the wind tunnel.

Develop an order-of-magnitude solution for the dispersion of atmospheric pollutants. The most commonly used models of atmospheric dispersion from continuous sources are the Gaussian plume models. For an infinite-line source such as might be used to simulate automotive emissions on a freeway, the model takes the form... 

The final step is calculation of dose to the public. The atmospheric dispersion model [7] typically uses a Gaussian plume model to predict exposure as a function of distance from the station the input is the predicted transient release of radionuclides from containment for each accident. The weather assumed is the worst weather occurring more than 10% of the time at the site. Exposure-to-dose calculations use standard ICRP recommended conversion factors. 

A smokestack plume is analogous to a groundwater plume, although the mechanism for mixing is turbulent diffusion instead of mechanical dispersion. The steady-state Gaussian plume model in air is traditionally... 

In Gaussian plume computations the change in wind velocity with height is a function both of the terrain and of the time of day. We model the air flow as turbulent flow, with turbulence represented by eddy motion. The effect of eddy motion is important in diluting concentrations of pollutants. If a parcel of air is displaced from one level to another, it can carry momentum and thermal energy with it. It also carries whatever has been placed in it from pollution sources. Eddies exist in different sizes in the atmosphere, and these turbulent eddies are most effective in dispersing the plume. 

One major item remains before we can apply the dispersion methodology to elevated emission sources, namely plume height elevation or rise. Once the plume rise has been determined, diffusion analyses based on the classical Gaussian diffusion model may be used to determine the ground-level concentration of the pollutant. Comparison with the applicable standards may then be made to demonstrate compliance with a legal discharge standard. 

BLP (Buoyant Line and Point Source Dispersion Model) is a Gaussian plume dispersion model associated witli aluminum reduction plants. 

In another review, Hoffert discussed the social motivations for modeling air quality for predictive purposes and elucidated the components of a model. Meteorologic factors were summarized in terms of windfields and atmospheric stability as they are traditionally represented mathematically. The species-balance equation was discussed, and several solutions of the equation for constant-diffusion coefficient and concentrated sources were suggested. Gaussian plume and puff results were related to the problems of developing multiple-source urban-dispersion models. Numerical solutions and box models were then considered. The review concluded with a brief outline of the atmospheric chemical effects that influence the concentration of pollutants by transformation. 

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