Secondary Pollutants: M.SC. IIIRD SEMESTER (3RD SEM) NOTES



Secondary pollutants include:

(A.)

            Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog. Smog is a kind of air pollution; the word “smog” is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulphur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

(B.)

            Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.

(C.)

            Peroxyacetyl nitrate (PAN) – similarly formed from NOx and VOCs and is a dangerous air pollutant mostly affects our respiratory system and nervous system.

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SOURCES OF AIR POLLUTION: M.SC. III SEMESTER (3RD SEM) NOTES

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