# 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 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