of Use and Disposal
In the past, one of the main issues with
production of nitric acid has been the release of nitrogen oxides,
particularly nitrogen dioxide, into the atmosphere. Huge steps
have been taken in the control of emissions by the industrial
sector (see controlling emissions), and transport
is now of much greater concern.
Nitrogen oxides are in fact produced naturally
by lightning, and are washed down by rain. This is responsible
for much of the "fixed" nitrogen used by plants. Human
activity, however, often results in high local levels (from transport
in a busy city, for example). The overall contribution from the
manufacture of nitric acid is very small.