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NO₂ and SO₂ sources; role in acid rain

Short answer

SO2 from burning coal/oil and smelting; NO2 from vehicle exhaust and high-temperature combustion. They oxidize to H2SO4 and HNO3, making rain acidic (pH<5.6). Remedies: low-sulfur fuels and flue gas desulfurization; catalytic converters on vehicles and shift to clean energy.

What are the sources of NO₂ and SO₂ pollutants in air? How do they play role in acid rain? Give two possible remedies of acid rain.

Sources

  • SO₂: burning of coal and petroleum products, smelting of sulphide ores (ZnS, Cu₂S), brick kilns, thermal power plants; natural source: volcanoes.
  • NO₂: vehicle exhaust and other high-temperature combustion (N₂ + O₂ → 2NO, then 2NO + O₂ → 2NO₂), thermal power plants, nitric acid and fertiliser industries; natural source: lightning.

Role in acid rain

2SO₂ + O₂ → 2SO₃ ;   SO₃ + H₂O → H₂SO₄
4NO₂ + O₂ + 2H₂O → 4HNO₃

H₂SO₄ and HNO₃ dissolve in rain water and make its pH fall below 5.6, which damages water bodies, soil, forests, buildings and metals.

Two remedies

  1. Use low-sulphur fuel and fit flue gas desulphurisation (lime scrubbers) in industry.
  2. Fit catalytic converters in vehicles and shift to clean energy such as hydropower and solar.

✓ Answer checked by Claude Opus 5.5 (high effort)

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