Q.Explain tropospheric pollution in 100 words.

The troposphere is the lowest layer of the atmosphere, extending up to about 10 km from the earth's surface, where all weather phenomena occur. Tropospheric pollution is caused by the presence of unwanted substances, called air pollutants, in this layer.

Air pollutants are of two main types:

1. Gaseous air pollutants: sulphur dioxide (SO2), oxides of nitrogen (NO, NO2), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons and ozone (O3).
2. Particulate pollutants: solid or liquid particles suspended in air, such as dust, mist, fumes, smoke and smog.

These pollutants arise mainly from the burning of fossil fuels in automobiles, thermal power plants and industries, as well as from volcanic eruptions and forest fires. Once in the troposphere they undergo further reactions — for example SO2 and NO2 are oxidised and dissolve in rain water to form acid rain, while NO2 and unburnt hydrocarbons react in sunlight to form photochemical smog. Tropospheric pollution causes respiratory diseases, damages plants and materials, corrodes buildings and monuments, and contributes to global warming through greenhouse gases such as CO2 and CH4.

Identify the troposphere as the layer of concern, list the two categories of pollutants (gaseous and particulate) with examples, and briefly connect them to their major consequences (smog, acid rain, greenhouse effect).

• Writing about the stratosphere/ozone layer instead of the troposphere — these are different layers with different pollution issues.
• Listing only gaseous pollutants and forgetting particulate pollutants.
• Exceeding/ignoring the word-limit guidance by writing an unstructured, overly long answer instead of a concise ~100-word account.