Photochemical smog is an atmospheric pollutant formed when sunlight reacts with substances like nitrogen oxides (NOx) and volatile organic compounds (VOCs). The key components are:
- Nitrogen Oxides (NOx): These originate from vehicle emissions, power generation, and industrial output. NOx is vital for smog formation as it reacts with VOCs under sunlight.
- Volatile Organic Compounds (VOCs): These are hydrocarbon substances that readily evaporate into the air. In the presence of sunlight, they react with NOx to produce ozone, a primary constituent of photochemical smog.
- High Temperature (> 25 degrees): Elevated temperatures accelerate the chemical reactions leading to smog. Warmer conditions increase VOC evaporation and boost the photochemical reactions that create smog.
The potential causes of photochemical smog are:
- Smoke, water vapour, and low temperature (> 25 degrees)
- NOx, SO2, and high temperature (> 25 degrees)
- NOx, VOCs, and high temperature (> 25 degrees)
- Smoke, NOx, and low temperature (< 25 degrees)
The definitive factors in photochemical smog formation are NOx, VOCs, and high temperature (> 25 degrees), identifying this as the correct combination.