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 ES-2. The effects of chemical reaction on concentrations of high, medium and
low reactivity source categories at a downwind receptor (Crestline).
The impact of spatial heterogeneity in emissions on the relationship between actual contributions
and emission contributions is illustrated n Figure ES-3. The Figure compares actual
contributions in air samples to emissions contributions for 15-km square areas around 8
receptors. Points that are not along the 1:1 line are for receptors/source categories where the
contributions in the air are significantly different from the local emissions inventory. The largest
deviations are at downwind receptors (Crestline and Lake Perris) that have relatively low
emissions near the receptor but are influenced by transport from high emission areas upwind.
This is an example of spatial heterogeneity in emissions that was resolved by the 5-km gridded
emissions inventory. In the real-world, there also could be fine-scale heterogeneity if, for
example, a monitor is located close to a large source (e.g., a point source or freeway
intersection).
H:\crca34-receptor\report\Final\ExecSum_r.doc
ES-4