Environmental Engineering Reference
In-Depth Information
x10
-4
100
4
Concentration at ground
surface
80
3
60
2
40
1
20
0
0
200
400
600
800
1000
x
Fig. 16.7 Concentration distribution at ground surface according to a Gaussian plume
solutions can be derived for the 2D situation. They decrease slowly after the peak is
reached at
350 m.
Figure
16.8
depicts ground concentrations along slices with constant
x
and
varying
y
. Clearly, all distributions are of Gaussian type. Global peak concentration
is found in the slice at
x ¼
300, the bell shaped concentrations
have small standard deviations, and local peak concentrations increase with
x
.
Beyond the slice with peak concentration, i.e. for
x >
300. For lower
x <
300, the standard deviations
increase, and the local maximum decreases with
x
.
Finally let us list the assumptions for the application of the Gaussian plume
model for the estimation of stack release:
The smokestack emission is continuous and constant
The terrain is relatively flat
The wind speed is constant in time and in elevation
In main wind direction, advection dominates over diffusion and dispersion
The diffusivities in horizontal and vertical direction are constant, i.e. they do not
change spatially and temporally
No settling velocity for the species
The pollutant is not involved in reactions, i.e. the species is neither produced nor
consumed; in particular there is no degradation
When the pollutants hit the ground, they are reflected and not absorbed
