Environmental Science: Numerical Questions – Air (Gaussian Plume Behaviour)

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Q1 Consider a tall stack emitting a pollutant at the rate 5.0 gms− 1 in the atmosphere where wind is blowing in X-direction with an average velocity of 2.0 ms− 1 at the stack height. What will be the maximum ground level concentration if the effective stack height is 30.0 m and the Gaussian plume is assumed with dispersion parameters σy = 50.0 m and σz = 30.0 m?

(1) ~180 μgm− 3

(2) ~320 μgm− 3

(3) ~240 μgm− 3

(4) ~415 μgm− 3

Answer: Option (2) ~320 μgm− 3

C x, y) = concentration at ground-level at the point (x, y , μg⟋m3

x = distance directly downwind, m

Y = horizontal distance from the plume centerline, m

Q = emission rate of pollutants

H = effective stack height

uH = average windspeed at the effective height of the stack, m⟋s

σy = horizontal dispersion coefficient (standard deviation) , m

σz = vertical dispersion coefficient (standard deviations) , m

Given Values,

Rate = 5.0 gms− 1

Velocity = 2.0 ms− 1

Effective Stack Height = 30.0 m

σy = 50.0 m

σz = 30.0 m

Mayank