Q14.Discuss in detail the photochemical smog emphasizing its formation, effects and mitigation. Explain the 1999 Gothenburg Protocol.

Photochemical smog is a type of air pollution formed when sunlight reacts with nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere.

Formation of Photochemical Smog

It involves primary pollutants (NOx, VOCs from vehicles and industries) reacting in the presence of sunlight to generate secondary pollutants like ozone (O3), peroxyacetyl nitrates (PANs), and aldehydes.

Effects of Photochemical Smog

• Causes respiratory problems and eye irritation in humans.
• Damages vegetation and agricultural crops.
• Degrades materials and infrastructure.

Mitigation Strategies

Mitigation focuses on reducing precursor emissions through stricter vehicle emission standards, industrial controls, cleaner fuels, and promoting public transport and renewable energy.

The 1999 Gothenburg Protocol

This protocol, under the UNECE Convention on Long-range Transboundary Air Pollution, aims to reduce acidification, eutrophication, and ground-level ozone. It sets national emission ceilings for Sulphur Dioxide (SO2), Nitrogen Oxides (NOx), Volatile Organic Compounds (VOCs), and Ammonia (NH3).