SSC JE Civil Engineering 30-Oct-2020 Shift 1 Paper

Emission from petrol engines contains a greater concentration of HC, ${\mathrm{CO}}_2$ , and CO while the four-stroke diesel engines (buses and trucks) contain a greater concentration of ${\mathrm{NO}}_{\mathrm{X}}$ 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, ${\mathrm{CO}}_{\mathrm{X}},{\mathrm{SO}}_{\mathrm{X}},{\mathrm{NO}}_{\mathrm{X}}$ , 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