Explain tropospheric pollution caused by oxides of nitrogen.

(N/A) Dinitrogen and dioxygen are the main constituents of air. These gases do not react with each other at a normal temperature.
At high altitudes when lightning strikes,they combine to form oxides of nitrogen. $NO_{2}$ is oxidised to nitrate ion,$NO_{3}^{-}$,which is washed into soil,where it serves as a fertilizer.
In an automobile engine,(at high temperature) when fossil fuel is burnt,dinitrogen and dioxygen combine to yield significant quantities of nitric oxide $(NO)$ and nitrogen dioxide $(NO_{2})$ as given below:
$N_{2(g)} + O_{2(g)} \xrightarrow{1405 \ K} 2 NO_{(g)}$
$NO$ reacts instantly with oxygen to give $NO_{2}$.
$2 NO_{(g)} + O_{2(g)} \rightarrow 2 NO_{2(g)}$
Rate of production of $NO_{2}$ is faster when nitric oxide reacts with ozone in the stratosphere.
$NO_{(g)} + O_{3(g)} \rightarrow NO_{2(g)} + O_{2(g)}$
The irritant red haze in the traffic and congested places is due to oxides of nitrogen.
Higher concentrations of $NO_{2}$ damage the leaves of plants and retard the rate of photosynthesis.
$NO_{2}$ is a lung irritant that can lead to an acute respiratory disease in children. It is toxic to living tissues also. Nitrogen dioxide is also harmful to various textile fibres and metals.