Definition
Photochemical smog forms when sunlight reacts with pollutants (nitrogen oxides and hydrocarbons, mainly from vehicle exhaust) — this is why smog is worse in strong sunlight, not typically noticed in the same way in summer's different conditions.
A catalytic converter in a vehicle's exhaust uses a catalyst (platinum-group metals) to convert harmful gases (CO, unburnt hydrocarbons, nitrogen oxides) into less harmful ones (CO, water, nitrogen) before they leave the exhaust.
Definition
Sulfur dioxide and nitrogen oxides (mainly from burning fossil fuels) dissolve in atmospheric water to form sulfuric and nitric acid, falling as acid rain — this damages forests, acidifies water bodies, and corrodes buildings.
Remember
Areas near heavy industry or with high fossil-fuel vehicle traffic see more acid rain, since that's where sulfur and nitrogen oxide emissions are concentrated.
Definition
Greenhouse gases (carbon dioxide, methane, water vapour) trap heat radiated from Earth's surface, warming the atmosphere — necessary in the right amount for a livable climate, but excess trapping (global warming) disrupts climate patterns.
Remember
Only carbon dioxide in air still matters enormously because greenhouse gases are extremely effective at absorbing and re-radiating heat even in small concentrations — a small percentage doesn't mean a small effect. Not every pollutant is a greenhouse gas; only ones whose molecular structure lets them absorb infrared (heat) radiation contribute to the effect.
Renewable sources — solar energy (heating, electricity) and wind energy (electricity via turbines) — reduce dependence on fossil fuels and their pollution. Air Quality Index (AQI) is a single number summarizing how polluted the air currently is and the associated health risk, letting the public and authorities respond quickly.
Remember
Children, the elderly, and people with respiratory conditions are the high-risk groups for air pollution, since their lungs are either still developing, already weaker, or already compromised.
Quick Recap
- ●Photochemical smog: sunlight + vehicle pollutants. Catalytic converter: turns harmful exhaust gases into safer ones
- ●Acid rain: SO/NO + atmospheric water acidic rainfall, from fossil fuel burning
- ●Greenhouse effect: CO, methane, water vapour trap heat — small concentration, large effect
- ●Solar and wind energy reduce fossil-fuel pollution; AQI summarizes current air pollution risk
- ●High-risk groups: children, elderly, people with respiratory conditions
