Environmental Engineering Reference
In-Depth Information
INDICATIONS OF IMPROVED AIR QUALITY
Although no technology for the control of CO
2
exists, substantial progress
has been made in the reduction of other emissions, and the skies over
Southern California are much cleaner as a result.This accomplishment has
been significant, for Southern California is the ideal location for the pro-
duction of photochemical smog: it has a huge car population, valleys that trap
stagnant air, and a frequent inversion layer that prevents emissions from dissi-
pating into the upper atmosphere. For many years it seemed as though the
region would be perpetually blighted, but technological advances have pro-
duced a noticeable improvement in air quality through a reduction of vehic-
ular emissions and other measures. By the 1990s, tailpipe emissions of carbon
monoxide and hydrocarbons had been reduced by 96 percent compared to
cars built in the 1960s, while oxides of nitrogen have been reduced by 76 per-
cent. The impressive progress that has been made in reducing air pollution
can be seen in the dramatic reduction of one index of smog severity, the con-
250
0.60
0.50
200
0.40
150
0.30
100
0.20
50
0.10
0
0.00
76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00
Days exceeding 1-hour federal standard
Maximum 1-hour average concentration (ppm)
FIGURE 1
Ozone air quality trends, South Coast Air Basin (California), 1976-2000. Left vertical
axis: days exceeding 1-hour federal standard. Right vertical axis: maximum 1-hour
average concentration (ppm). (South Coast Air Quality Management District)
