A plume model or a puff model is traditionally
used when investigating the influence of exhaust
from a chimney, being the core of assessment today.
As for the predictions of the influence on the
atmospheric environment by pollutants emitted
from motor vehicles and the whole city, for example,
various kinds of numerical simulation models have
been recently developed for this purpose.
For understanding the atmospheric influence
due to vehicle emission, the diffusion of exhaust
gases along a roadside and photochemical reactions
(especially ozone formation) over a broad area
are important phenomena. A calculation result
using an air quality model for the South Coast
Air Basin (SCAB) in California and measurments
have predicted the ozone concentration. There
is a plan (SIP) enforcing exhaust reduction by
2010 for atmosphere improvement in the SCAB. The
current ozone concentration was calculated using
the certification model UAM from US EPA, and the
ability of UAM was confirmed. The, ozone concentration
after emission regulation of SIP was then predicted.
As a result of the simulation under SIP conditions,
it became clear that the ozone concentration was
satisfied in the environmental standard. The relationships
between the highest ozone concentration in the
SCAB and amounts of NOx and HC emissions
were found and it became clear that the reduction
of HC was effective in this area.
The use of an electric vehicle was examined
for the SIP achievement. It became clear that
countermeasures for replacing the so-called high-emitter
or old vehicles with new ones was effective as
a result of the mobile exhaust prediction.
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