Environmental Engineering Reference
In-Depth Information
z
u
y
x
Figure 9.4
Line source.
z
u
y
l
x
Figure 9.5
Area source.
φ
=
angle between the source axis and the prevailing wind direction (which by convention
always blows in the
x
direction), degrees
x
=
distance of the receptor from the source axis in the direction of the wind, m
Note that the distance parallel to the source axis does not appear in equation (9.8) because the
concentration does not change in that direction. Equation (9.8) should not be used when
φ
is less
than 45
◦
.
9.2.4.5 Steady-State Area Source
Emissions from an urban area can be considered as emanating from a bunch of parallel line sources,
as depicted in Figure 9.5. The ground-level mass concentration
c
(
x
)
of pollutant at a downwind
