Air that contains harmful particles and gases is said to be polluted. Some air pollution occurs naturally. But many types of air pollution are the result of human activities.
Many natural processes such as forest fires, dust storms release smoke and dust particles into the air. Volcanoes emit clouds of dust and poisonous gases along with ash. Which gas is emitted by volcanoes? Termites and cows also release large amounts of methane in the air. Considerable electrical discharges in the atmosphere produce nitrogen oxides.
Most of the air pollution is the result of burning fossil fuels, such as coal, petroleum, and natural gas. Nearly half of the air pollution comes from cars and other motor vehicles. Factories and power plants that burn coal or oil release poisonous gases into the air. Burning fossil fuels and incineration release carbon monoxide (CO), nitrogen oxides (NO, NO₂), and sulphur oxides (SO₂, SO₃). Table 10.1 shows the effects produced by air pollutants.
C(s) + O2(g) (limited) → CO(g) S(s) + O2(g) → SO2(g) N2(g) + O2(g) → 2NO(g) 2NO(g) + O2(g) → 2NO2(g)
| Air Pollutant | Physical Properties | Sources | Harmful Effects |
|---|---|---|---|
| Carbon monoxide | Colourless, odourless and poisonous gas | Incomplete burning of wood, fuels and vehicle exhaust. | Headache, brain damage, death. |
| Sulphur dioxide | Colourless gas with unpleasant and irritating odour | Power stations and industries using fossil fuels | Breathing difficulties, bronchitis, emphysema, lung cancer, acid rain and greenhouse effect |
| Oxides of nitrogen | NO is colourless, odourless gas soluble in water. NO₂ is reddish brown gas with pungent odour soluble in water. Both are highly toxic gases | Exhaust of motor vehicles, power stations and industries using fossil fuels | Coughs, headaches lung diseases, acid rain and greenhouse effect (global warming) |
1. Write three human activities that are responsible for air pollution.
2. Write three natural processes that are contributing to air pollution.
3. List main sources of the following air pollutants: