Question

In metropolitan cities like Bombay and Calcutta, the major atmospheric pollutants are

• A. Carbon monoxide and oxides of sulphur
• B. Hydrocarbons and hot air
• C. Pollens and marsh gas
• D. Ozone

Answer 1

The correct option is A Carbon monoxide and oxides of sulphur

Natural background levels of carbon monoxide (CO) fall in the range of 10-200 ppb. Levels in urban areas are highly variable, depending upon weather conditions and traffic density. For protection of both public health and welfare, EPA set a 8-hour primary standard at 9 parts per million (ppm) and a 1-hour primary standard at 35 ppm. In the presence of an adequate supply of $O_2$, most CO produced during combustion is immediately oxidised to carbon dioxide ($C{O}_2$).

However, this is not the case in spark ignition engines. Thus, the major source of atmospheric CO is the spark ignition combustion engine. The most important sources of $S{O}_2$ are fossil fuel combustion. Coal burning is the single largest man-made source of $S{O}_2$ accounting for about 50% of annual global emissions, with oil burning accounting for a further 25-30%. In 2010, EPA revised the primary $S{O}_2$ level by establishing a new 1-hour standard at a level of 75 parts per billion (ppb).