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

Dr. Manishika Jain- Join online Paper 1 intensive course. Includes tests and expected questions.

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 σ_{y}=50. 0 m and σ_{z}=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/m^{3}

*x* = distance directly downwind, m

Y = horizontal distance from the plume centerline, m

Q = emission rate of pollutants

H = effective stack height

*u*_{H} = average windspeed at the effective height of the stack, m/s

σ_{y}= horizontal dispersion coefficient (standard deviation), m

σ_{z} = vertical dispersion coefficient (standard deviations), m

Given Values,

Rate = 5.0 gms^{−1}

Velocity = 2.0 ms^{−1}

Effective Stack Height = 30.0 m

σ_{y}=50. 0 m

σ_{z}=30.0 m

-Mayank