Environmental Engineering Reference
In-Depth Information
Notice that the normalized model results and measurements fit best for NO
2
.
However, for NO
2
the model systematically shows a slight underestimation of the
concentrations. At the moment it is not fully clear why and further research is
necessary. For NO the model predicts a slightly faster decay of the concentrations
behind the vegetation. For PM the model does not follow the measurements. The
measurements even show an increase in the concentrations due to the vegetation
while the model shows a pattern similar to those of the nitrogen oxides. Notice
that for PM only a limited measurement data set was available. For this reason it
would be to soon to draw hard conclusions on this and further research remains
necessary.
Veg -model
Ref -model
Veg -Meting
Ref -meting
Veg -model
Ref -model
Veg -Meting
Ref -meting
1.4
1.4
1.2
1.2
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
50
100
150
0
50
100
150
x
x
Fig. 1.
Normalised mean nitrogen oxides concentrations (NO left, NO
2
right) at 2 m height.
Green bar indicates the location of the vegetation, the red boxes the line sources. Green and red
dots represent the ECN measurements, continuous lines: model results. Red: Along the reference
measurement line, green: in front of and behind the vegetation barrier. Mean wind is blowing
from the left
Veg -model
Ref -model
Veg -Meting
Ref-meting
Veg-model
Ref -model
Veg -Meting
Ref -meting
1.2
1.2
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
50
100
150
0
50
100
150
x
x
Fig. 2.
Normalized mean PM concentrations (PM
2.5
left, PM
10
right) at 2 m height. Similar to
Fig. 1
In all cases the model predicts an increase in concentration in front of and just
behind the vegetation barrier. This is due to the decrease in wind speed at the
location of the emission source. Further away from the vegetation a decrease of
about 5% and for NO even more than 10% can be found (see
Fig. 3).
