Next time you
drive past a petroleum refinery, an automobile manufacturing plant, or any
large industrial facility, take a look at all the stacks, pipes, and vents. Imagine
how difficult it must be to quantify all of the air pollutants released by that
facility. Each facility typically contains a diverse set of processes that emit
different pollutants at different rates that must each be accounted for
separately. Now imagine taking on the task of compiling emissions for all industrial
facilities, large and small, across the United States. And what about
highway emissions? Consider all of the cars, trucks, and motorcycles driving on
a busy street or highway— how would you go about quantifying the emissions from
the different models being driven at various speeds?
having to account for emissions from all motor vehicles on every stretch of
road in the United States,
from the busiest interstate to the tiniest local road. Next, think about the
hundreds of thousands of other sources of air pollution across the nation.
There are off-road mobile sources, ranging from large engines used in
construction and agriculture to small engines used for yard maintenance and
recreation. There are nonindustrial stationary sources, including emissions
from heating homes and commercial buildings. There are forest fires, waste
disposal facilities, and gasoline stations. The list goes on and on.
From EM Magazine
, December 2006