On Sat, 3 Oct 2015 21:43:35 +0100, "Richard"
wrote:


The whole 'cleaning up emissions' business has everything to do with the
climate change lobby.

You may be right if you are including all the emissions but I thought
this subject referred to oxides of nitrogen, I also thought the
particular significant one was nitrogen dioxide, which has an acrid
smell and is implicated in asthma problems. As it cools it is in
equilibrium with N2O4.

It is these components of exhaust that combine with other chemicals in
sunlight to form a photochemical smog in hot places like california.

I also thought it less of a problem in UK where rainfall is high
enough to wash these nitrogen compounds out as nitrous and nitric acid
(which is a fertiliser in these low dilutions we used it added to
irrigation water for ericaceous plants to counteract the calcium which
made the water alkaline) and there is not enough sunlight to cause the
problem experienced elsewhere.

So while NOx emissions in towns and cities can cause health problems
it is insignificant in the countryside other than making grass grow
more??

AJH