Re: What is a simple way to identify the different air pollutants in the air?

There is no "simple" way to identify all of the air pollutants, but there 
are some ways to identify a few.  If you can borrow a high-volume sampler 
or tape sampler from either your local air pollution control agency or a 
university or community college in your area, it will work better than 
vaseline and allow you to separate organic particles from inorganic 
particles.  These instruments collect particles on filter paper by pulling 
air through the filter with a pump.  You can determine the total 
particlulate matter by weighing the filter paper before and after 
collection (you need a chemical balance for this).  You should do the 
before-and-after weighing with your cotton and vaseline system also.  Using 
filter paper,, however, you can then dissolve out the organic particles 
with benzene or a similar solvent (alcohol might work), dry and reweigh the 
filter paper, and you will have separated the organic from the inorganic 
particles.  If you try washing out the organics in the vaseline system, it 
doesn't work as well, but you can determine the inorganic particles (the 
vaseline washes out with the organics).

You can get a qualitative estimate of nitrogen dioxide from the brown color 
in the air (take photos on successive days, perhaps) because nitrogen oxide 
gives smog its characteristic brown color.  You can also collect rainwater 
and check the pH, which gives you some idea of the combined concentration 
of sulfur and nitrogen oxides.

Refs:  Wark and Warner: AIR POLLUTIION: ITS ORIGIN AND CONTROL; Vesilind, 
Pierce, and Weiner: ENVIRONMENTAL ENGINEERING; any air pollution textbook.