Environmental Chemistry

• Atmosphere — the blanket of air around Earth: ~78% N₂, ~21% O₂, ~0.04% CO₂, plus traces.

• Primary vs secondary — CO, SO₂, NOx, particulates & hydrocarbons are emitted directly; smog & acid form afterwards.

CO blocks O₂ in blood; SO₂ & NOx make acid rain; particulates harm lungs. In Karachi/Lahore winter smog, still air traps it all near the ground.

Acidic rain (pH 4–4.5) kills fish, eats marble buildings (CaCO₃) and damages forests. Control: scrub SO₂ with lime, fit catalytic converters.

One Cl• destroys tens of thousands of O₃ molecules → the ozone hole. The Montreal Protocol (1987) banned CFCs. Slide to release more chlorine and watch the hole grow.

• Greenhouse gases — CO₂ & CH₄ absorb the IR the ground radiates and send it back, trapping heat.

Too much → global warming: melting glaciers, rising seas, extreme weather. Pakistan's Himalayan glaciers feed the Indus.

• BOD — oxygen microbes use up; high BOD = heavily polluted.

Eutrophication: nitrate/phosphate runoff feeds an algal bloom; the algae die, decompose, and strip the water of oxygen. Heavy metals (Pb, Hg) are toxic too.

• Green chemistry — prevent pollution at the source instead of cleaning it up later.

Principles: prevent waste, maximise atom economy, use safer solvents & renewable feedstocks, use catalysts, design biodegradable products.

1. Atmosphere & its layers.
2. Air pollution: primary vs secondary.
3. Acid rain: SO₂/NOx → H₂SO₄/HNO₃.
4. Ozone: the CFC Cl• catalytic chain & the hole.
5. Greenhouse effect → global warming.
6. Water: BOD/COD, eutrophication; green chemistry.