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CHAPTER 14 Plume Dispersion

CHAPTER 14 Plume Dispersion. Objectives:. Assess environmental impact of an emission source in terms of legislated standards for:. Toxicity, and Odour. In Ontario this constitutes regulation 419/05:. http:www.rwdi.com/regulation419/. Pg. 176 course notes.

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CHAPTER 14 Plume Dispersion

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  1. CHAPTER 14Plume Dispersion Objectives: Assess environmental impact of an emission source in terms of legislated standards for: • Toxicity, and • Odour

  2. In Ontario this constitutes regulation 419/05: http:www.rwdi.com/regulation419/ Pg. 176 course notes

  3. Our task is to estimate the impact of an emission source from an industrial plant:

  4. Plume dispersion occurs in the y- and z-directions Plume is convected by the wind in the x-direction Z-axis starts from ground level

  5. Turbulent dispersion: y-direction: z-direction: Where sy and sz are dispersion parameters that must be estimated

  6. Recall from our treatment of particle diffusion: where Dis the particle diffusivity Pg. 49-50 course notes

  7. Diffusion mechanisms: • Solute (gas or liquid) diffusion occurs by random molecular motion. • Particle diffusion occurs by random Brownian motion. • Plume dispersion occurs by random turbulent motion.

  8. syandsz must be estimated

  9. Ground-level concentrations will depend on … Wind … Wind rose shows average direction and magnitude of the wind vector Pg. 178 course notes

  10. Atmospheric stability … Dry adiabatic lapse rate (stable, neutral atmosphere) Natural balance between hydrostatic head,  g dA dZ, and pressure forces Pg. 179 course notes

  11. Super-adiabatic lapse rate: A “buoyant” atmosphere Pg. 180 course notes

  12. Sub-adiabatic lapse rate: Pg. 180 course notes

  13. The Gaussian plume model: The concentration of material downwind in the x-direction varies as the inverse of the local transport velocity, i.e., A Gaussian type distribution is used in the y-direction:

  14. If we choose The distribution will provide an integrated concentration of unity across the transverse cross-section … starting to look like a normal distribution!

  15. Z- direction requires special treatment … When the “edge” of the plume reaches the ground … we assume perfect “reflection”!

  16. (z - H) term accounts for the above ground contribution (z + H) term accounts for the imaginary source below ground

  17. Final form of the Gaussian plume model: • Product of the y- and z-direction distributions • Q is the emission rate in mass per unit time

  18. Variation of C with x is contained in the behaviour of y and z with downstream position, x, from the emission source.

  19. Fig 6-14 and 7-14, pg. 184 and 185

  20. Stability classes A - F Table 1-14 pg. 186

  21. Mathematical models for sy

  22. Mathematical models for sz • for class C, and • piecewise (in x) for other different classes

  23. Pg. 187 course notes

  24. But … Pg. 188 course notes

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