CRC Report No. A-34 - Coordinating Research Council

April 2005
Comparison of Source Contributions at Crestline in
Experiments 12 (no chemical decay) and 11 (with chemical decay)
120
100
Expt 11 (with chemical decay) - ppbC
80
60
40
Gasoline - day
Gasoline - night
(Biogenics) x 2 - day
(Biogenics) X 2 - night
(CNG/aged + LPG) x 10 - day
(CNG/aged + LPG) x 10 - night
1:1
20
0
0 20 40 60 80 100 120
Expt 12 (no chemical decay) - ppbC
Figure 4-9. The effects of chemical reaction on concentrations of high, medium and low
reactivity source categories at a downwind receptor (Crestline).
Findings from Experiments 9-12
• CMB performs very well for 3-D cases under ideal conditions where source profiles are
well characterized, source profiles are not co-linear, there is no chemical decay, and no
sampling noise.
• Limitations to CMB performance in ideal 3-D cases are more related to co-linear source
profiles than either chemical decay or random measurement noise.
• CMB performance was very robust against effects of chemical decay in an ideal case
with fairly simple source contributions.
• The experiments performed leave open a possibility that chemical decay could be a
greater impediment to CMB in more complex cases with more sources that are more colinear
or for source categories with greater dependence on more reactive species to
properly apportion the source..
• CMB performance was very robust against random sampling noise in an ideal case with
fairly simple source contributions. Experiment 8 showed that CMB performance also
was robust against random sampling noise with more complex sources and profiles.
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