Weekend/Weekday Ozone Observations in the South Coast Air Basin

O3, NO and NO2* (ppm)
0.20
0.16
0.12
0.08
Carry Over
O 3, NO 2, and PAN
HONO and HCHO
NO, CO, and VOC
CO
NO 2
Azusa, Summer 1995
O 3 Inhibition
(due to NO
titration)
O 3 Accumulation a
t = t O3max - t NO=O3
Post Maximum O 3
Declining photolysis rate,
increasing mixing and ventilation,
and titration of O 3 by fresh NO
emissions
3.0
2.5
2.0
1.5
1.0
CO (ppm)
0.04
NO
0.5
O 3
0.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour (PDT)
t NO=O3 on weekdays
0.0
t NO=O3 on weekends
WE O3 WD O3 WE NO WD NO
WE NO2* WD NO2* WE CO WD CO
a. O3 accumulation rate = [O3(max) - O3 (t NO=O3 )]/(t O3max - t NO=O3 )
Figure 2-1. Average summer 1995 diurnal variations of O3, NO, NO2, and CO at Azusa during
weekday and weekend. The shorter ozone inhibition period and higher rate of ozone formation
are the main factors causing higher ozone on weekends.
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