Solution:
Emission from petrol engines contains a greater concentration of HC, CO2 , and CO while the four-stroke diesel engines (buses and trucks) contain a greater concentration of NOX in addition to thick smoke and particulate matter.
AIR POLLUTANTS can be broadly classified into two general groups -
1. A primary pollutant is an air pollutant emitted directly from a source. Eg. Particulates, COX,SOX,NOX , Bacteria, Fog, Soot, Dew, etc
2. A secondary pollutant is not directly emitted as such, but forms when other pollutants (primary pollutants) react in the atmosphere. Eg. Ozone, PAN, PBN, PPN, Smog, CFC, and Acid Rain
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