CRC Report No. A-34 - Coordinating Research Council

April 2005
(c)
average all hours
80
70
60
50
40
30
20
Lake Per r i s
Long Beach
Crestline Van Nuys Haw thorn
Diamond Bar
Lake Perris Anaheim LAX
LAX
Anaheim
Haw Van thorn Nuys
Long Beach Diamond Bar Lake Perris
Crestline
Gasoline
Diesel
Solvent
Biogenic
Backgd
CNG and Aged
LPG
Anahei m
10 Crestline
Di amond Bar Di amond Bar
AnaheiCrestline
mHawthor n
Long Beach
Lake Per r i s
0.00 Long Lake Anahei Di amond Van Beach Per mNuys
r Bar
0 Crestline Hawthor Van Di amond Nuysn
Bar i s
Anahei m
0 10 20 30 40 50 60 70 80
1:1
Actual Contr i buti on (%)
Figure 4-3. Comparison of CMB contributions to actual contributions for experiment 1 in
Round 4 at each receptor averaged over (a) 6-9 am (b) 1-4 pm and (c) all hours.
Hourly source apportionment results are compared in greater detail in Figures 4-4 for experiment
1 at Anaheim in Round 4. Anaheim was one of the better performing sites for CMB in Round 4.
Figure 4-4a shows all of the 13 source categories that CMB reported for this case in Round 4.
CMB was able to resolve a large number of categories in Round 4 because detailed source
profiles were available. Figure 4-4b shows the actual contributions aggregated to match Figure
4-4a. CMB was able to follow some major temporal features in the actual contributions such as
(1) the rush hour for on-road, gasoline-powered vehicle emissions, (2) the afternoon peak in
biogenics and (3) the daytime peak in degreasing. However, many of the other hour-to-hour
variations reported by CMB are noisy or incorrect. A large part of this noise likely results from
the sampling noise introduced into the “ambient” samples. With only four sampling days, each
hour is averaged over just 4 samples. These comparisons show that with the size of dataset
considered here (four days of continuous samples) CMB performance is much better for daily
average source contributions than for individual hours.
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